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BEGIN:VEVENT
SUMMARY:R. Singh
DTSTART:20240902T055000Z
DTEND:20240902T060000Z
DTSTAMP:20260404T095423Z
UID:QOART/1
DESCRIPTION:Title: Opening\nby R. Singh as part of Quantum Optics and Related Topics
\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/QOART/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. V. Masalov
DTSTART:20240902T060000Z
DTEND:20240902T070000Z
DTSTAMP:20260404T095423Z
UID:QOART/2
DESCRIPTION:Title: Unsolved problem in quantum optics\nby A. V. Masalov as part of Q
uantum Optics and Related Topics\n\n\nAbstract\nThe report is devoted to t
he problem of quantum calculations of radiation fields in nonlinear optica
l media under conditions of powerful light beams\, i.e. when the number of
photons is huge. The attempts known to the author to solve this problem a
re considered.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. V. Akimov
DTSTART:20240902T074000Z
DTEND:20240902T091000Z
DTSTAMP:20260404T095423Z
UID:QOART/3
DESCRIPTION:Title: Toward quantum simulations with Thulium atoms\nby A. V. Akimov as
part of Quantum Optics and Related Topics\n\n\nAbstract\nBose-Einstein co
ndensation (BEC) is a powerful tool for a wide range of research activitie
s\, a large fraction of which is related to quantum simulations. Various p
roblems may benefit from different atomic species. Thulium atoms possess d
ipole moment of 4 Bohr magneton in the ground state\, allowing long-term i
nteractions. It also has number of non-chaotic low-field Feshbach resonanc
es\, allowing fine control of the near-filed interactions. It also has rel
atively simple level structure compared to the other magnetic lanthanoids
and thus is a quite promising subject for applications in quantum simulati
ons.\nNevertheless\, cooling down novel species interesting for quantum si
mulations to BEC temperatures requires a substantial amount of optimizatio
n and is usually considered to be a difficult experimental task. Here we r
eport on implementation of the Bayesian machine learning technique to opti
mize the evaporative cooling of thulium atoms and achieved BEC in an optic
al dipole trap. Two dipole traps were used: 532 nm light and 1064 nm light
\, in both the condensation was achieved. We also analyzed the atomic loss
mechanism for the 532 nm optical trap\, used in the Bose-condensation exp
eriment\, and compares it with the alternative and more traditional micron
-range optical dipole trap.\nWhile the condensate of the thulium atom has
a lot of applications in quantum simulations and other areas of physics\,
it can also serve as a unique diagnostic tool for many atomic experiments.
In the present study\, the Bose-Einstein condensate of the thulium atom w
as successfully utilized to diagnose an optical lattice and detect unwante
d reflections in the experiments with the 1064 nm optical lattice\, which
will further be used in a quantum gas microscope experiment.\nThis work wa
s supported by Rosatom in the framework of the Roadmap for Quantum computi
ng (Contract No. 868-1.3-15/15-2021 dated October 5\, 2021).\n
LOCATION:https://stable.researchseminars.org/talk/QOART/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:D.A. Chermoshentsev
DTSTART:20240902T092000Z
DTEND:20240902T102000Z
DTSTAMP:20260404T095423Z
UID:QOART/4
DESCRIPTION:Title: Nonlinear Photonics for Coherent Computing and Signal Generation\
nby D.A. Chermoshentsev as part of Quantum Optics and Related Topics\n\n\n
Abstract\nOur scientific interests lie in the fields of nanophotonics\, qu
antum optics\, and quantum computing. We are engaged in the development an
d study of the nonlinear and quantum properties of the electromagnetic fie
ld in integrated photonic circuits. The use of such integrated systems all
ows for the development of compact devices with unique properties: stable
laser sources with low phase noise\, spectrometers\, gyroscopes\, sensors\
, sources of coherent and soliton frequency combs\, microwave signal gener
ators\, sources of non-classical states of light\, as well as optical and
quantum computers. The presentation will discuss the latest results obtain
ed from research in these systems.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:R. Singh
DTSTART:20240902T103000Z
DTEND:20240902T110000Z
DTSTAMP:20260404T095423Z
UID:QOART/5
DESCRIPTION:Title: The formation of Schrodinger cat-like states in the process of sponta
neous parametric down-conversion\nby R. Singh as part of Quantum Optic
s and Related Topics\n\n\nAbstract\nThe formation of Schrodinger cat-like
states during the spontaneous parametric down-conversion process (SPDC) is
studied when the pump mode is considered quantum and depleted. The Schrod
inger cat-like state is formed in the fundamental and second harmonic mode
s\, and the negativity in both modes is studied for certain initial state
conditions and interaction lengths. The Wigner function is used to visuali
ze qualitatively Schrodinger cat-like states.\n\nhttps://arxiv.org/abs/240
5.14526\n
LOCATION:https://stable.researchseminars.org/talk/QOART/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:E. A. Anashkina
DTSTART:20240902T120000Z
DTEND:20240902T130000Z
DTSTAMP:20260404T095423Z
UID:QOART/6
DESCRIPTION:Title: Phase-sensitive symmetry breaking in microresonators with Kerr nonlin
earity\nby E. A. Anashkina as part of Quantum Optics and Related Topic
s\n\n\nAbstract\nSpontaneous symmetry breaking (SSB) is a fundamentally im
portant concept known in many areas of physics: particle physics\, condens
ed matter physics\, and optics\, to name a few. In photonics\, there has b
een an increasing interest in studying symmetry breaking\, chiral and nonr
eciprocal light propagation in optical macro- and microresonators with cub
ic nonlinearities. Here\, we demonstrate theoretically and experimentally
that linear coupling due to the backscattering between two counterpropagat
ing modes in a microresonator with Kerr nonlinearity leads to extreme sens
itivity of the intensity asymmetry of light states to the relative phase b
etween the bidirectional pumps of equal power. In the absence of linear co
upling\, the relative pump phase does not affect counterpropagating intrar
esonator intensities\, and two asymmetric states arise due to spontaneous
symmetry breaking. Contrariwise\, in the presence of weak linear intermode
coupling\, the asymmetry of the states is deterministically controlled vi
a changes in phase (for all phases except 0 and π). Spontaneous symmetry
breaking at zero phase is suppressed when the linear intermode coupling is
increased\, while for the π phase it can be enhanced\, so that the overa
ll threshold for the spontaneous symmetry breaking can be significantly lo
wer for nonzero linear coupling. These results are important for fundament
al understanding of the processes in Kerr resonators and other systems wit
h Kerr-like nonlinearities and linear intermode coupling and have high pro
spects for the development of photonic devices such as ultrasensitive sens
ors. Moreover\, the study of such systems also allows one to obtain fundam
ental results that can be used outside of optics due to quantum-optical an
alogies (for example\, for studying the well-known Bose-Hubbard dimer).\n\
nThe work was supported by the Russian Science Foundation\, grant No.20-72
-10188-P.\n\nE.A. Anashkina\, A.V. Andrianov\, “Phase-sensitive symmetry
breaking in bidirectionally pumped Kerr microresonators\,” arXiv prepri
nt arXiv:2407.07594 (2024).\n
LOCATION:https://stable.researchseminars.org/talk/QOART/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. K. Fedorov
DTSTART:20240902T134000Z
DTEND:20240902T144000Z
DTSTAMP:20260404T095423Z
UID:QOART/7
DESCRIPTION:Title: Quantum complexity and quantum information technologies\nby A. K.
Fedorov as part of Quantum Optics and Related Topics\n\n\nAbstract\nCompl
exity is the cornerstone concept of physics\, and it plays a special role
in the context of quantum many-body physics. Recent progress in developing
computational devices based on quantum effects and demonstrations of solv
ing various tasks using them has actualized the question of the origin of
the quantum advantage. Although various attempts to quantify and character
ize the nature of quantum computational advantage have been made\, this qu
estion in the general context remains open: There is no universal approach
that helps to define a scope of problems that quantum computers are able
to speed up\, theoretically and in practice. In this talk\, we review an a
pproach to this question based on the concept of complexity and reachabili
ty of quantum states. On the one hand\, the class of quantum states that i
s of interest for quantum computing should be complex\, i.e. non-simulatab
le with classical computers with less than exponential resources. On the o
ther hand\, such quantum states should be reachable on a practical quantum
computer. This means that a unitary corresponding to the transformation o
f quantum states from initial to desired can be decomposed in a sequence o
f single- and two-qubit gates with of no more than polynomial in the numbe
r of qubits. Our consideration paves the way towards understanding the sco
pe of problems that can be solved by a quantum computer by formulating a s
equence of statements and conjectures on various sets of quantum states.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. A. Sukhorukov
DTSTART:20240903T060000Z
DTEND:20240903T070000Z
DTSTAMP:20260404T095423Z
UID:QOART/8
DESCRIPTION:Title: Photon-pair generation and quantum measurements with metasurfaces
\nby A. A. Sukhorukov as part of Quantum Optics and Related Topics\n\n\nAb
stract\nWe present the theoretical and experimental advances of our group
on quantum photon-pair generation through spontaneous parametric down-conv
ersion in nonlinear metasurfaces\, underpinning quantum entanglement engin
eering at a sub-wavelength scale for photon shaping with tailored polariza
tion and spatial correlations. In particular\, we demonstrate experimental
ly the generation of spatially entangled photon pairs through spontaneous
parametric down-conversion from a metasurface incorporating a nonlinear th
in film of lithium niobate covered by a silica meta-grating and achieve pr
ecise control of the emission angle of photons. We also outline the applic
ations of metasurfaces quantum imaging combining ghost and all-optical sca
nning at infrared wavelengths and perform single-shot characterization of
the indistinguishability between two photons.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.B. Mikhalychev
DTSTART:20240903T074000Z
DTEND:20240903T091000Z
DTSTAMP:20260404T095423Z
UID:QOART/9
DESCRIPTION:Title: Quantum measurement as a tool for probabilistic transformation of qua
ntum light states\nby A.B. Mikhalychev as part of Quantum Optics and R
elated Topics\n\n\nAbstract\nSpecific properties of quantum measurements (
backaction on the measured object\, randomness of the outcomes) lead to
“hidden” character of quantum information and hinder investigation of
quantum systems. On the other hand\, inevitable influence of the measuring
device on the quantum system can serve as an instrument for steering it t
o a useful target state. The talk is devoted to that aspect of quantum mea
surements: special measurement types capable of creating various target st
ates\; general ideas of measurement-induced control of quantum states\; in
terpretation of dissipative (non-unitary) dynamics of quantum systems in t
erms of continuous measurements and its usage for generation of non-classi
cal quantum-optical states. Namely\, a class of “elimination” measurem
ents is defined\, discussed\, and shown to be efficient for quantum light
state manipulation. Further\, the idea is extended to the field of quantum
imaging and an approach to conditional enhancement of photonic state sens
itivity to the illuminated object sub-Rayleigh features is proposed. The c
lose connection between dissipative non-unitary dynamics and measurement-i
nduced steering of a quantum state makes the concept of “elimination”
measurements also fruitful for description of an optical system subjected
to nonlinear coherent loss and showing its capability of generating sub-Po
issonian quantum-optical states.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:I.E. Sinayskiy
DTSTART:20240903T092000Z
DTEND:20240903T110000Z
DTSTAMP:20260404T095423Z
UID:QOART/10
DESCRIPTION:Title: Quantum Simulation of Open Quantum Systems\nby I.E. Sinayskiy as
part of Quantum Optics and Related Topics\n\n\nAbstract\nA simulation of
quantum systems is one of the most exciting use cases for quantum computer
s. The simulation of closed quantum systems\, or Hamiltonian simulation\,
has been explored in recent years. Novel methods have been developed\, imp
roving the widely used and wellknown Suzuki Lie Trotter product formulas.
However\, in many practical situations\, one must consider unavoidable int
eraction with the thermal environment. The success of quantum computers in
simulating physical systems has led to the development of quantum algorit
hms to simulate open quantum systems in the faulttolerant setting. However
\, these algorithms are limited to the Suzuki Lie Trotter product formulas
of the first and second order. In this talk\, I will give an overview of
the quantum simulation of quantum systems and focus on our recent work of
reducing the gate complexity in the simulation of an open quantum system b
y using two methods that rely on randomisation.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:S. Chaturvedi
DTSTART:20240903T120000Z
DTEND:20240903T133000Z
DTSTAMP:20260404T095423Z
UID:QOART/11
DESCRIPTION:Title: Bose’s derivation of the Planck's distribution\, his notion of ind
istinguishability and its quantum counterpart: A comparison\nby S. Cha
turvedi as part of Quantum Optics and Related Topics\n\n\nAbstract\nAfter
a brief discussion of the notion of indistinguishabilty introduced by S N
Bose in his seminal 1924 paper dealing with the derivation of Planck’s d
istribution we proceed to discuss its quantum counterpart. We highlight th
e commonalities and differences between all possible statistics that arise
after implementing respective notions of indistinguishabilty in the two s
cenarios and bring out the role the theory of symmetric functions plays in
achieving this objective.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.B. Klimov
DTSTART:20240903T134000Z
DTEND:20240903T151000Z
DTSTAMP:20260404T095423Z
UID:QOART/12
DESCRIPTION:Title: Discrete phase-space description of N-partite quantum systems: from
visualization to quantification of quantum correlations\nby A.B. Klimo
v as part of Quantum Optics and Related Topics\n\n\nAbstract\nWe review th
e application of the discrete phase-space approach to analyzing quantum co
rrelations in many body systems. Starting with a microscopic description\,
we proceed to analyze global features of quantum states detectable in col
lective measurements\, mainly focusing on N-qubit systems in the macroscop
ic limit N>>1. Applications to quantification/identification of quantum co
rrelations\, quantum tomography\, phase transitions\, quantum thermalizati
on\, and stability under local noise are outlined. A generalization to hig
her local dimensions is discussed.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:P. K. Panigrahi
DTSTART:20240904T060000Z
DTEND:20240904T070000Z
DTSTAMP:20260404T095423Z
UID:QOART/13
DESCRIPTION:Title: Meso and Macroscopic Quantum States of Light\nby P. K. Panigrahi
as part of Quantum Optics and Related Topics\n\n\nAbstract\nWe investigat
e the nature of correlated photons from three dipole-coupled two-level ato
mic systems and find the clear signatures of the entangled matter states o
n the nature of the emitted photons. The presence of two phases\, as predi
cted by Dicke a long time back\, is evident in the far-field spectrum. The
phase transition between these two phases and the behaviour of concurrenc
e\, discord and monogamy in both these phases are explicated. The effect o
f the atomic configuration is pointed out in the optical domain. We then i
nvestigate another macroscopic state of condensed photons\, where photonic
superfluidity and supersolidity are pointed out with exact solutions of t
he relevant mean field equations: nonlinear Schrodinger equation with a so
urce. The earlier experimental observation of the superfluid phase opens t
he way for the possible realization of photonic supersolidity. We further
highlight the deep connection between entanglement\, coherence\, and path
predictability in the much-studied multi- slit experiments.\n\nRef:\n\n(1)
M. K. Parit et al.\, “Correlated photons of desired characteristics fro
m a dipole coupled three-atom system”\, OSA Continuum 2 (8)\, pp. 2293-2
307 (2019).\n\n(2) Dynamical phase transition of photon condensate in an o
ptical cavity Neeraj\, MK Parit\, VM Vyas\, PK Panigrahi\,Journal of the O
ptical Society of America B 38 (2)\, 476-481\n\n(3) A scheme to observe un
iversal breathing mode and Berezinskii–Kosterlitz–Thouless phase trans
ition in a two-dimensional photon gas\, VM Vyas\, PK Panigrahi\, J Banerji
\, Physics Letters A 378 (20)\, 1434-1437\n\n(4) Coherence\, path predicta
bility\, and concurrence: A triality AK Roy\, N Pathania\, NK Chandra\, PK
Panigrahi\, T Qureshi\, Physical Review A 10\,(3)\, 032209\n
LOCATION:https://stable.researchseminars.org/talk/QOART/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:O. V. Tikhonova
DTSTART:20240904T074000Z
DTEND:20240904T084000Z
DTSTAMP:20260404T095423Z
UID:QOART/14
DESCRIPTION:Title: Entanglement and correlations of photons in bright squeezed vacuum l
ight\nby O. V. Tikhonova as part of Quantum Optics and Related Topics\
n\n\nAbstract\nSpatial and spectral features as well as strong photon corr
elations of non-classical multi-photon squeezed electromagnetic fields are
discussed. We consider the theoretical approach based on the Schmidt mode
analysis and able to describe analytically peculiarities of such bright s
queezed light with high agreement with experimental data. Methods to contr
ol and manage the mode content\, degree of squeezing and photon entangleme
nt are analyzed. Their advantages and applied prospects are highlighted. P
ractical applications based on the non-classical features of squeezed fiel
ds for precise quantum measurements and strong coupling to atomic systems
are discussed.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. E. Teretenkov
DTSTART:20240904T092000Z
DTEND:20240904T101000Z
DTSTAMP:20260404T095423Z
UID:QOART/15
DESCRIPTION:Title: Multimode quantum master equations: linear dynamics beyond quadratic
generators\nby A. E. Teretenkov as part of Quantum Optics and Related
Topics\n\n\nAbstract\nWe present several examples of quantum master equat
ions such that the dynamics of moments up to any finite order of bosonic c
reation and annihilation operators is (exactly) closed and linear.\nNamely
\, we consider the quantum master equations which occur in the case of ave
raging of unitary dynamics with quadratic generators with respect to class
ical Levy fields\, in particular with respect to Poisson and Wiener stocha
stic processes. We show that the dynamics of the moments of any fixed orde
r is described by the closed system of ordinary linear differential equati
ons.\nWe discuss some recent physical applications of these results.\n\nTh
e talk is based on the works:\n\nT. Linowski\, A. Teretenkov\, L. Rudnicki
\, Physical Review A\, 106 (2022)\, 052206.\n\nD. D. Ivanov\, A. E. Terete
nkov\, Math. Notes\, 112:2 (2022)\, 318-322.\n\nA. E. Teretenkov\, Math. N
otes\, 107:4 (2020)\, 695-698.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:W. V. Pogosov
DTSTART:20240904T120000Z
DTEND:20240904T123000Z
DTSTAMP:20260404T095423Z
UID:QOART/16
DESCRIPTION:Title: Effects of photon statistics in wave mixing on a single qubit\nb
y W. V. Pogosov as part of Quantum Optics and Related Topics\n\n\nAbstract
\nWe theoretically consider wave mixing under the irradiation of a single
qubit by two photon fields. The first signal is a classical monochromatic
drive\, while the second one is a nonclassical light. Particularly\, we ad
dress two examples of a nonclassical light: (i) a broadband squeezed light
and (ii) a periodically excited quantum superposition of Fock states with
0 and 1 photons. The mixing of classical and nonclassical photon fields g
ives rise to side peaks due to the elastic multiphoton scattering. We show
that side peaks structure is distinct from the situation when two classic
al fields are mixed. The most striking feature is that some peaks are abse
nt. Thus\, the analysis of peak amplitudes can be used to probe photon sta
tistics in the nonclassical mode. A cascade of two-level superconducting a
rtificial atoms – a source and a probe – strongly coupled to a semi-in
finite waveguide is a promising tool for observing such non-trivial phenom
ena. The probe atom can scatter an antibunched output from the source\, th
ereby generating the field with specific properties. We experimentally dem
onstrate wave mixing between non-classical light from the coherently pumpe
d source and another coherent wave acting on the probe. We observe unique
features in the wave-mixing stationary spectrum that cannot be reproduced
by mixing two classical waves on the probe. These features are well descri
bed by the theory for a strongly coupled cascaded system of two atoms.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. E. Afanas'ev
DTSTART:20240904T134000Z
DTEND:20240904T144000Z
DTSTAMP:20260404T095423Z
UID:QOART/17
DESCRIPTION:Title: Quantum metrology with atom chip\nby A. E. Afanas'ev as part of
Quantum Optics and Related Topics\n\n\nAbstract\nThe goal of quantum metro
logy is to increase the sensitivity of physical fields measuring. It can b
e achieved by using quantum mechanics effects such as interferometry of qu
antum states\, squeezing\, etc. Quantum sensors used as instruments for hi
gh sensitivity measurements reached outstanding results in laboratory cond
itions. There is currently a growing trend towards outdoor experimentation
. The main development trend is the decreasing of dimensions and power con
sumption of quantum sensor in comparison with used sensors in classical ap
proaches. Increasing sensitivity of outdoor sensors will allows us to move
to the next technological level.\nAmong various types of quantum sensors\
, the sensors using neutral atoms are promising. To increase the quantum s
enser sensitivity the approach of atomic state interference is used.\nAtom
interferometry is considered as a platform for high precision fundamental
experiments and for solving numerous applied problems [1]. For instance\,
microwave atomic clock used interference pattern of Ramsey fringe for hig
h stability of frequency standards. The precision of quantum sensors is li
mited by the quantum projection noise. Therefore\, the number of atoms for
ming the interference pattern is the cornerstone of quantum sensor. To rea
ch high precision of quantum sensors based on atom interferometry the effe
ctive source of cold atoms is necessary. There are three types of atoms so
urces can be used for atom interferometry: (1) atomic beam\; (2) cold atom
s in magneto-optical trap (MOT)\; (3) ultracold atoms trapped on atom chip
. The use of the first type of atom source leads to quantum sensors of lar
ge spatial dimensions. Cold atoms from MOT are actively used in quantum se
nsors\, for instance\, in atomic gravimeter [2\,3]. The drawback of MOT as
an atomic source is the temperature of atomic ensemble. In case of sub-Do
ppler cooling the temperature is about several microkelvins. Lower tempera
tures require evaporative cooling. Unfortunately\, MOT is not suitable for
evaporative cooling\, which is usually done in a magnetic trap.\nThe atom
chip operation is based on a cold atom trapping near the microwire. In th
is case a high gradient of magnetic field can be achieved relatively easy.
Approach for ultracold atom source sensor baser on atom chip has been dem
onstrated with high bandwidth [4]. Until now\, most demonstrated atom chip
s have been technically sophisticated\, with multiple layers of microwires
to cool and trap atoms. We demonstrated single-layer atom chip which can
be used as atom source for atom interferometry and quantum sensors [5]. Th
e new type of single-layer atom chip developed\, which makes it possible t
o increase the number of atoms up to 5?107 [6]. The magnetic trapping of a
toms gives the possibility to use evaporative cooling to reach the tempera
tures below 1 mkK. It gives us the possibility of coherent manipulations w
ith atomic ensemble.\n\nThe study was supported by the Russian Science Fou
ndation\, grant No. 23-22-00255.\n\nReferences\n\n[1] R. Geiger\, et al.\,
AVS Quantum Sci. 2\, 024702 (2020).\n\n[2] V. Menoret\, et al.\, Sci Rep
8\, 12300 (2018).\n\n[3] Pan-Wei Huang\, et al.\, Metrologia 56\, 045012 (
2019).\n\n[4] J. Rudolph\, et al.\, New J. Phys. 17\, 065001 (2015).\n\n[5
] A.E. Afanasiev\, et al.\, Optics & Laser Technology\, 148\, 107698 (2022
).\n\n[6] P. Skakunenko\, et al.\, Chinese Optics Letters\, 22\, 060201 (2
024).\n
LOCATION:https://stable.researchseminars.org/talk/QOART/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:L.L. Sanchez-Soto
DTSTART:20240905T060000Z
DTEND:20240905T073000Z
DTSTAMP:20260404T095423Z
UID:QOART/18
DESCRIPTION:Title: Quantum Superresolution in Time and Frequency\nby L.L. Sanchez-S
oto as part of Quantum Optics and Related Topics\n\n\nAbstract\nAccurate t
ime is at the core of many modern technologies. I will present new schemes
that allow one to achieve the ultimate quantum precision for the estimati
on of the time (or frequency) offset of an incoherent mixture of ultrashor
t pulses at the single-photon level. Amazingly\, these techniques are able
to resolve temporal separations 10 times smaller than the pulse duration\
, as well as imbalanced intensities differing by a factor of $10^2$. This
represents an improvement of more than an order of magnitude over the best
standard methods based on intensity detection and pave the way for new te
chnologies in this field.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. N. Rubtsov
DTSTART:20240905T074000Z
DTEND:20240905T084000Z
DTSTAMP:20260404T095423Z
UID:QOART/19
DESCRIPTION:Title: Samplers: their description and its complexity\nby A. N. Rubtsov
as part of Quantum Optics and Related Topics\n\n\nAbstract\nBosonic sampl
ers are quantum optical devices operating with multimode interference of n
on-classical fields\, and are intended to provide practical demonstration
of quantum advantage.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. P. Alodjants
DTSTART:20240905T092000Z
DTEND:20240905T102000Z
DTSTAMP:20260404T095423Z
UID:QOART/20
DESCRIPTION:Title: Physical graph structures for Quantum and Quantum-like Simulators\nby A. P. Alodjants as part of Quantum Optics and Related Topics\n\n\nAb
stract\nCurrently speedup of information transmission represents one of th
e vital interdisciplinary problems in computer science\, physics and engin
eering. Recently\, various systems based on photonic information processin
g have been suggested to get advantages in information processing. Typical
ly\, such a system mimics some quantum-like physical process that enables
to solve NP-hard problem established by means of specific graph\, or the n
etwork. In my talk\, I will analyze the quantum -inspired algorithms based
on special network and/or quantum devices (simulators)\, leading to an ac
celeration of the solution of some Karp problem. I discuss recently propos
ed by us novel quantum material (computational “hardware”) concept\, w
hich enables interaction of two-level systems with the photonic field in t
wo-dimensional materials possessing complex network interface . The multic
hannel (multimode) structure of matter–field interaction leads to speedu
p of photonic information processing. The results obtained pave the way fo
r the design of new photonic circuits\, quantum networks for efficient pro
cessing of optical information.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. V. Khmelev
DTSTART:20240905T120000Z
DTEND:20240905T130000Z
DTSTAMP:20260404T095423Z
UID:QOART/21
DESCRIPTION:Title: Satellite quantum communication: experiments in Russia and prospects
\nby A. V. Khmelev as part of Quantum Optics and Related Topics\n\n\nA
bstract\nAbstract: The report will be devoted to satellite quantum key dis
tribution (QKD)\, a direction in quantum communication that allows using a
satellite to organize a secure communication channel on a global scale in
order to share cryptographic keys between users. Based on the recent rese
arch of our group [1]\, the results of establishing a quantum-secured link
between the Zvenigorod and Nanshan ground stations using the Micius satel
lite will be presented. Moreover\, we validate the simulation outcomes of
our QKD model for the developed realistic ground station using obtained ex
perimental findings\, which\, as we believe\, provide valuable insights on
the applied side of the satellite-based QKD technology.\n\n[1] A Khmelev
et al. Opt. Express 32\, 11964-11978 (2024)\n\n[2] A Khmelev et al. Entrop
y 25(4)\, 670 (2023)\n
LOCATION:https://stable.researchseminars.org/talk/QOART/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:B. I. Bantysh
DTSTART:20240905T134000Z
DTEND:20240905T151000Z
DTSTAMP:20260404T095423Z
UID:QOART/22
DESCRIPTION:Title: Resolution limits for multiple single-photon emitters\nby B. I.
Bantysh as part of Quantum Optics and Related Topics\n\n\nAbstract\nFluore
scent microscopy is essential for many biological applications. It uses dy
e molecules or quantum dots that emit photons to create images. The resolu
tion of such emitters is limited by the Rayleigh criterion. In recent year
s\, several attempts have been made to overcome this limit for resolving t
wo single-photon emitters. However\, for emitters with unbalanced intensit
ies\, the absolute error in determining the distance increased as the sour
ces moved closer together [1]. In a recent study\, we demonstrated that a
more accurate model\, which takes into account photon statistics\, allows
for the resolution of sources with arbitrary intensity ratios [2]. In this
report\, an analysis of the resolution limits of complex two-dimensional
objects composed of a larger number of sources will be presented.\n\n[1] K
. A. G. Bonsma-Fisher\, W.-K. Tham\, H. Ferretti\, and A. M. Steinberg\, R
ealistic sub-rayleigh imaging with phase-sensitive measurements\, New Jour
nal of Physics 21\, 093010 (2019).\n\n[2] K. G. Katamadze\, B. I. Bantysh\
, A. Yu. Chernyavskiy\, Yu. I. Bogdanov\, and S. P. Kulik\, Breaking Rayle
igh's curse for two unbalanced single-photon emitters using BLESS techniqu
e. arXiv preprint arXiv:2112.13244 (2024).\n
LOCATION:https://stable.researchseminars.org/talk/QOART/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:E. Losero
DTSTART:20240906T063000Z
DTEND:20240906T073000Z
DTSTAMP:20260404T095423Z
UID:QOART/23
DESCRIPTION:Title: Nitrogen Vacancy (NV) centers in diamond for bio-sensing\nby E.
Losero as part of Quantum Optics and Related Topics\n\n\nAbstract\nNitroge
n-vacancy (NV) centers are color-defects in the diamond crystal lattice wh
ich have raised a lot of attention in the last decades for their promising
sensing capabilities (especially for magnetic field and temperature)\, ba
sed on spin-dependent photoluminescence. Moreover\, diamond biocompatibili
ty and good sensitivity at room temperature naturally lead to biological a
pplications. Both bulk diamond and nanodiamonds can be used in this contex
t\, each presenting its own advantages and challenges.\n\nIn this presenta
tion\, I’ll describe our recent results in both directions. On one side
I'll discuss how diamond chips can be nanostructured and used as substrate
s for cellular growth. On the other\, I'll show how nanodiamonds can be us
ed for nanoscale thermometry inside cells. Both approaches can be combined
with existing measurements techniques and give new insights on many biolo
gical processes which are still not completely understood.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. B. Fedotov
DTSTART:20240906T074000Z
DTEND:20240906T084000Z
DTSTAMP:20260404T095423Z
UID:QOART/24
DESCRIPTION:Title: Four-wave mixing in photonic crystal fibers for generation of tailor
ed quantum states of light\nby A. B. Fedotov as part of Quantum Optics
and Related Topics\n\n\nAbstract\nWe demonstrate a versatile fiber-optic
platform for the generation of tailored quantum states of light\, designed
to enhance the performance of quantum sensing and imaging. The developed
platform is based on optical fibers of special design\, including photonic
-crystal fibers (PCFs).\n\nThe design of optical fibers is optimized to pr
ovide an ultrahigh-contrast generation of entangled photon pairs confined
to entanglement volumes many orders of magnitude smaller than the entangle
ment volumes attainable through spontaneous parametric down-conversion. Fo
ur-wave mixing (FWM) with cross-polarized pump and cross-polarized sideban
ds enables efficient generation of entangled photon pairs. Generation of c
ross-polarized photon pairs is achieved by coupling the laser pump into or
thogonal polarization modes of a highly birefringent\, highly nonlinear\,
anomalously dispersive PCF. The contrast of photon pairs against the Raman
noise is enhanced by setting the pump wavelength to lie deeply within the
anomalous dispersion region of the fiber. Broadband quantum states of lig
ht generated via vectorial FWM are tailored\, by varying the pump waveleng
th and polarization geometry\, from a high-purity\, low-dimensional entang
led state to a high-entropy entangled state in a space of a very high dime
nsionality.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yu. A. Nosal
DTSTART:20240906T093000Z
DTEND:20240906T100000Z
DTSTAMP:20260404T095423Z
UID:QOART/25
DESCRIPTION:Title: Dynamics of moments of higher orders in exactly solvable models of t
he theory of open quantum systems\nby Yu. A. Nosal as part of Quantum
Optics and Related Topics\n\n\nAbstract\nIn this work we consider quantum
master equations for which the dynamics can be obtained explicitly. A Leib
niz-type formula has been derived which allows one to compute the action o
f the conjugate Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) generator on
the product of the creation and annihilation operators\, up to higher orde
rs. Also\, the Heisenberg equations for arbitrary moments of higher orders
of the birth and annihilation operators in the case of a generator in the
form of GKSL quadratic in terms of the bosonic creation and annihilation
operators have been obtained in explicit form. Moreover\, solutions of suc
h equations in the case of time-dependent coefficients have been obtained.
In addition\, the Isserlis-Wick theorem was proved in the notations used
in the paper and the consistency of the results obtained earlier with the
theorem was demonstrated. On the basis of the Heisenberg equations obtaine
d in the paper\, analogous equations were derived for the quantum master e
quation arising after averaging the dynamics by a quadratic generator over
a classical Poisson process. This allowed us to show that the dynamics of
arbitrary moments of finite order of the creation and annihilation operat
ors in this case is completely determined by a finite number of linear dif
ferential equations.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:M.V. Fedorov
DTSTART:20240906T130000Z
DTEND:20240906T133000Z
DTSTAMP:20260404T095423Z
UID:QOART/26
DESCRIPTION:Title: Variations of the degree of angular entanglement in noncollinear reg
imes of Spontaneous Parametric Down-Conversion (SPDC)\nby M.V. Fedorov
as part of Quantum Optics and Related Topics\n\n\nAbstract\nAs known\, th
e process of Spontaneous Parametric Down-Conversion in birefringent crysta
ls (SPDC) produces states of photon pairs [1-3] which can be entangled. Th
e variables of the biphoton wave function can be different and characteriz
ing different degrees of freedom of photons: their polarizations\, or prop
agation angles\, or frequencies of photons ω1 and ω2. In the last case o
ne can speak about spectral entanglement of sates characterized by the wav
e function Ψ(ω1\, ω2). The phenomenon of spectral entanglement and its
degree were rather thoroughly investigated in the work [4]\, both theoreti
cally and experimentally . On the other hand\, the double Fourier transfor
mation of Ψ(ω1\, ω2) gives the temporal biphoton wave function Φ(t1\,
t2)\, in which the time variables t1 and t2 can be interpreted as the arri
val times of photons to detectors. In terms of the temporal wave function
Φ(t1\, t2) one can speak about temporal entanglement of biphoton states\,
which is discussed in this talk.\n\n1. D.N. Klyshko\, JETP Lett\, 6\, 90
(1967).\n\n2. S.E. Harris\, M.K. Oshman\, and R.L. Byer\, PRL\, 18\, 732 (
1967).\n\n3. D. Magde\, H. Marr\, PRL\, 18\, 905 (1967).\n\n4. G. Brida\,
V. Caricato\, M.V. Fedorov\, M. Genovese\, S.P. Kulik\, EPL\, 87\, 64003 (
2009).\n
LOCATION:https://stable.researchseminars.org/talk/QOART/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.A. Kalachev
DTSTART:20240906T134000Z
DTEND:20240906T141000Z
DTSTAMP:20260404T095423Z
UID:QOART/27
DESCRIPTION:Title: Quantum hashing via single-photon states\nby A.A. Kalachev as pa
rt of Quantum Optics and Related Topics\n\n\nAbstract\nA quantum hashing i
s a promising generalization of the cryptographic hashing concept on the q
uantum domain. In this case\, the hash function encodes a classical input
state into a quantum state so that to optimize the trade-off between one-w
ay property and collision resistance. In the present work\, we develop a q
uantum hashing technique wherein a quantum hash is constructed as a sequen
ce of single-photon qubits [1] or qudits [2]. A proof-of-principle impleme
ntation of the quantum hashing protocol using orbital-angular momentum enc
oding of single photons demonstrates good agreement with theoretical predi
ctions. In particular\, it shows that the number of qudits decreases with
increase of their dimension for an optimal ratio between collision probabi
lity and decoding probability of the hash [2]. The prospects of increasing
dimension of information carriers\, which makes quantum hashing with sing
le photons more efficient\, are discussed [3].\n\n[1] D. A. Turaykhanov\,
D. O. Akat'ev\, A. V. Vasiliev\, F. M. Ablayev\, and A. A. Kalachev. Quant
um hashing via single-photon states with orbital angular momentum. Physica
l Review A\, 104\, 052606 (2021)\n\n[2] D.O. Akat’ev\, A.V. Vasiliev\, N
.M. Shafeev\, F.M. Ablayev\, A.A. Kalachev. Multiqudit quantum hashing and
its implementation based on orbital angular momentum encoding. Laser Phys
ics Letters 19\, 125205 (2022)\n\n[3] D. A. Turaykhanov\, N.M. Shafeev\, A
. V. Vasiliev\, F. M. Ablayev\, and A. A. Kalachev. Quantum hashing with o
rbital angular momentum and polarization encoding. (to be submitted)\n
LOCATION:https://stable.researchseminars.org/talk/QOART/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rajiuddin Sk
DTSTART:20240907T060000Z
DTEND:20240907T063000Z
DTSTAMP:20260404T095423Z
UID:QOART/28
DESCRIPTION:Title: Role of Stark shift effect in preserving quantum correlations\nb
y Rajiuddin Sk as part of Quantum Optics and Related Topics\n\n\nAbstract\
nIn this talk\, I will present an analysis of the dynamics of quantum corr
elations in a\nsystem of two two-level atoms undergoing two-photon transit
ions via an intermediate virtual\nstate. Each atom is coupled to a dissipa
tive reservoir at zero temperature\, with the presence\nof the Stark shift
effect playing a crucial role. We explore the exact expressions for Bures
\ndistance entanglement\, trace distance discord\, and local quantum uncer
tainty under two\ndifferent environmental initial conditions: the ground s
tate and the first excited state. Notably\,\nthe first excited state revea
ls the influence of both Stark shift parameters\, whereas the\nground stat
e only highlights one. Our findings indicate that quantum correlations can
be\nmaintained for extended periods due to the Stark shift effect\, with
a more pronounced impact\nobserved in non-Markovian reservoirs\, even at m
inimal Stark shift values. Additionally\, we\nidentify a sudden change phe
nomenon in local quantum uncertainty\, marked by an abrupt\nshift in the d
ecay rate. These results are crucial for understanding how to preserve qua
ntum\ncorrelations\, which are essential for optimizing performance in qua
ntum information\nprocessing.\n\nReference:\n\n(1) Chandra\, Nitish Kumar\
, Rajiuddin Sk\, and Prasanta K. Panigrahi. "Preservation and\nenhancement
of quantum correlations under Stark effect." Journal of Modern Optics 70.
4 (2023):\n232-242.\n\n(2) Bashkirov\, E. K.\, and M. S. Rusakova. "Entang
lement for two-atom Tavis–Cummings model with\ndegenerate two-photon tra
nsitions in the presence of the Stark shift." Optik 123.19 (2012): 1694-16
99.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. Yu. Karasev
DTSTART:20240907T064000Z
DTEND:20240907T071000Z
DTSTAMP:20260404T095423Z
UID:QOART/29
DESCRIPTION:Title: High order quantum corrections to the parametric approximation\n
by A. Yu. Karasev as part of Quantum Optics and Related Topics\n\n\nAbstra
ct\nThis report presents the kinetic equations for an open two-level syste
m weakly interacting with a dissipative laser field. Corrections to the pa
rametric approximation in all orders of perturbation theory are calculated
. We studied the contribution of the coherent state of the environment to
the renormalization of the initial conditions.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:J. Lugani
DTSTART:20240907T074000Z
DTEND:20240907T084000Z
DTSTAMP:20260404T095423Z
UID:QOART/30
DESCRIPTION:Title: Integrated platforms for quantum information processing\nby J. L
ugani as part of Quantum Optics and Related Topics\n\n\nAbstract\nIntegrat
ed optical platforms are bound to play crucial role in developing quantum
optical technologies. Benefitting from their inherent stability\, scalabil
ity and tunability\, different integrated platforms are being widely explo
red for the generation and manipulation of photonics qubits. In this work\
, I will provide a brief overview of how such quantum tasks are realized o
n optical chips. In addition\, I will focus on a novel platform based on t
hin film lithium niobate to develop such quantum optical devices\n
LOCATION:https://stable.researchseminars.org/talk/QOART/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.V. Andrianov
DTSTART:20240907T092000Z
DTEND:20240907T110000Z
DTSTAMP:20260404T095423Z
UID:QOART/31
DESCRIPTION:Title: Kerr squeezing in optical waveguides and its use to improve the sens
itivity of interferometers\nby A.V. Andrianov as part of Quantum Optic
s and Related Topics\n\n\nAbstract\nSqueezed light is one of the key resou
rces of photonic quantum technology. Among the various applications of squ
eezed light states\, measurement beyond the standard quantum limit is one
of the most prominent. Squeezed light is regularly used in large-scale gra
vitational wave detectors. Among the various nonlinear interactions that c
an produce squeezing\, the optical Kerr effect is particularly interesting
because it can potentially be implemented in a wide variety of materials
and arrangements. It does not require phase matching\, and one can use opt
ical waveguides to achieve long interaction lengths. The amount of squeezi
ng can reach significant levels due to the tight confinement in the fibres
(and thus high intensity). However\, the advantages of generating bright
squeezed states in third-order nonlinear media are somewhat masked by diff
iculties in using them for applications such as interferometry\, because t
he uncertainty distribution in phase\nspace for these states is tilted wit
h respect to both phase and amplitude quadrature. In this talk\, we review
various techniques for generating squeezed light in optical waveguides (a
nd in particular optical fibres)\, and discuss a novel approach to overcom
e difficulties in applying Kerr-squeezed light to quantum-enhanced interfe
rometry. One popular approach to work with the Kerr-squeezed tilted states
is to create a polarisation-squeezed state by combining two such states i
n orthogonal polarisations of the same spatial mode. In a polarisation squ
eezed state the fluctuations of a particular Stokes parameter are smaller
than in a coherent state with the same mean polarisation state. In such se
tups\, it is important to use pulsed light and to protect the polarisation
modes from cross-Kerr interaction by temporally separating the pulses. Th
is can be done efficiently and in a very stable manner using polarisation-
maintaining fibres and/or polarisation-sensitive group delay compensators.
We report on a very stable approach to build an all-fiber setup for the g
eneration of Kerr-squeezed light states based on polarisation-maintaining
silica fibers [1]\, and on a demonstration of interferometric sensitivity
enhancement beyond the shot noise limit using these states [2]. We also pr
esent the first experimental observation of squeezed light generation in c
halcogenide fibres. Chalcogenide glass fibres have 3-5 orders of magnitude
higher nonlinearity than standard\nsilica fibres. They also exhibit a wid
e range of mid-IR transparency. This stimulates the study of chalcogenide
(and other soft highly nonlinear glasses such as tellurite) as it promotes
the\ndevelopment of non-classical light sources in an extended wavelength
range that is not readily accessible with current technologies. In the ta
lk we also discuss some aspects of numerical modelling and optimisation [3
] of squeezed light generation in nonlinear waveguides made of different m
aterials (silica\, soft tellurite and chalcogenide glasses)\, paying speci
al attention to parasitic effects such as Raman scattering.\n\n[1] N. Kali
nin\, T. Dirmeier\, A. A. Sorokin\, E. A. Anashkina\, L. L. Sánchez‐Sot
o\, J. F. Corney\, G. Leuchs\, and A. V. Andrianov\, "Observation of Robus
t Polarization Squeezing via the Kerr Nonlinearity in an Optical Fiber\,"
Adv Quantum Tech 6(3)\, 2200143 (2023).\n\n[2] N. Kalinin\, T. Dirmeier\,
A. A. Sorokin\, E. A. Anashkina\, L. L. Sánchez-Soto\, J. F. Corney\, G.
Leuchs\, and A. V. Andrianov\, "Quantum-enhanced interferometer using Kerr
squeezing\," Nanophotonics 12(14)\, 2945–2952 (2023).\n\n[3] A. V. Andr
ianov\, N. A. Kalinin\, A. A. Sorokin\, E. A. Anashkina\, L. L. Sánchez-S
oto\, J. F. Corney\, and G. Leuchs\, "Optimizing the generation of polariz
ation squeezed light in nonlinear optical fibers driven by femtosecond pul
ses\," Opt. Express 31(1)\, 765 (2023).\n
LOCATION:https://stable.researchseminars.org/talk/QOART/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:C.H. Raymond Ooi
DTSTART:20240907T120000Z
DTEND:20240907T133000Z
DTSTAMP:20260404T095423Z
UID:QOART/32
DESCRIPTION:Title: Correlated Raman photon pairs and finite-temperature quantum memory<
/a>\nby C.H. Raymond Ooi as part of Quantum Optics and Related Topics\n\n\
nAbstract\nQuantum communication technology would need a reliable quantum
system for quantum information storage. Many studies of optical quantum me
mory involve the Raman scheme for writing and reading of optical pulses an
d single photons that carry quantum information. Optical quantum memory is
an essential component in quantum information technology\, particularly f
or secure long-distance quantum communication networks. Many quantum memor
y schemes have been proposed and demonstrated experimentally but there are
limitations\, especially with regard to practicality and scalability. We
will discuss our work towards room temperature quantum memory which has be
en regarded as formidable due to the rapid decoherence and broadened absor
ption/emission peaks. Counter-propagating laser schemes can be applied to
achieve optimal performances by overcoming these problems. This would be a
step forward to realizing a practical quantum network. \n\nWe will discu
ss the use of Heisenberg-Langevin-Maxwell coupled equations to study quant
um correlations and relative squeezing of Raman photon pairs for forward a
nd backward propagating gemetries with arbitrary pump and control lasers u
sing double Raman scheme. We generalized the quantum theory of stimulated
Raman scattering to study the spatial-temporal dynamics of photons during
storage and retrieval stages of quantum memory with all dissipative mechan
isms included\, such as atomic motion\, collisions and radiation baths. We
will discuss the effects of controllable laser pulses\, velocity distribu
tion and atomic initial conditions (like atomic frequency comb). Our study
involves numerical solutions of Heisenberg-Langevin-Maxwell coupled equat
ions generalized analytical solutions that can be used to study the quantu
m memory performance like storage time\, efficiency and the correlations b
etween storage and retrieval photons.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/32/
END:VEVENT
BEGIN:VEVENT
SUMMARY:O.V. Lychkovskiy
DTSTART:20240907T134000Z
DTEND:20240907T151000Z
DTSTAMP:20260404T095423Z
UID:QOART/33
DESCRIPTION:Title: Many-body correlation functions by the recursion method: symbolic ne
sted commutators\, universal operator growth hypothesis and pseudomode exp
ansion\nby O.V. Lychkovskiy as part of Quantum Optics and Related Topi
cs\n\n\nAbstract\nRecursion method is a technique to solve coupled Heisenb
erg equations in a tridiagonal operator basis constructed via Lanczos algo
rithm. We report an implementation of the recursion method that addresses
quantum many-body dynamics in the nonperturbative regime. The implementat
ion has three key ingredients: a computer-algebraic routine for symbolic c
alculation of nested commutators\, a procedure to extrapolate the sequence
of Lanczos coefficients according to the universal operator growth hypoth
esis and the pseudomode expansion addressing the large time asymptotics. W
e apply the method to calculate infinite-temperature correlation functions
for spin-1/2 systems on one- and two-dimensional lattices. The method all
ows one to accurately calculate transport coefficients. As an illustration
\, we compute the diffusion constant for the transverse-field Ising model
on a square lattice. The talk is based on arXiv 2401.17211\, 2407.12495. \
n\nThe research is supported by the Russian Science Foundation under the g
rant No. 24-22-00331.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:L.C. Kwek
DTSTART:20240908T070000Z
DTEND:20240908T073000Z
DTSTAMP:20260404T095423Z
UID:QOART/34
DESCRIPTION:Title: Integrated Silicon Photonics\nby L.C. Kwek as part of Quantum Op
tics and Related Topics\n\n\nAbstract\nQuantum and classical neural networ
ks with integrated photonics have recently emerged as a promising approach
towards efficient and high-performance information processing. By harness
ing the unique features of photons\, such as their quantum nature\, ecofri
endliness or high-speed characteristics\, these integrated systems have be
en applied to optical neural network and boson sampling. We report recent
work done in this direction.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:T. Qureshi
DTSTART:20240908T074000Z
DTEND:20240908T091000Z
DTSTAMP:20260404T095423Z
UID:QOART/35
DESCRIPTION:Title: Generalized Two-Particle Interference\nby T. Qureshi as part of
Quantum Optics and Related Topics\n\n\nAbstract\nTwo-photon interference i
s an interesting quantum phenomenon that is usually captured in two distin
ct types of experiments\, namely the Hanbury-Brown-Twiss (HBT) experiment
and the Hong-Ou-Mandel (HOM) experiment. First\, a duality relation\, betw
een the particle distinguishability and the visibility of two-particle int
erference\, is derived. The distinguishability of the two particles\, aris
ing from some internal degree of freedom\, puts a bound on the sharpness o
f the two-particle interference they can produce\, in a HOM or HBT kind of
experiment. This points to a common origin of both the experiments which
are generally considered distinct. Then a generalized formulation of two-p
article interference is presented. The HOM and the HBT effects emerge as s
pecial cases in the general analysis. A two-particle interference experime
nt\, which is intermediate between the two effects\, is proposed and analy
zed. Thus two-particle interference is shown to be a single phenomenon wit
h various possible implementations\, including the HBT and HOM setups.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/35/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. Rai
DTSTART:20240908T092000Z
DTEND:20240908T110000Z
DTSTAMP:20260404T095423Z
UID:QOART/36
DESCRIPTION:Title: Quantum Physics with integrated waveguide arrays\nby A. Rai as p
art of Quantum Optics and Related Topics\n\n\nAbstract\nWithin the last fe
w years\, lattices of evanescently coupled optical waveguides have proven
to be a versatile platform for investigating a variety of quantum effects.
The possibility of engineering various interactions by design makes these
arrays an experimentally accessible tool for studying a variety of effect
s from a large number of fields of physics. Another salient feature of thi
s system is the possibility of controlling the exact initial conditions fo
r the light propagating inside the array. Moreover\, the decoherence rate
in this system is very low\, even for longer propagation distances. In thi
s talk\, we present a summary of some of our studies on optical waveguide
arrays.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/36/
END:VEVENT
BEGIN:VEVENT
SUMMARY:I. I. Dzhadan
DTSTART:20240908T120000Z
DTEND:20240908T123000Z
DTSTAMP:20260404T095423Z
UID:QOART/37
DESCRIPTION:Title: Многофтонная запутанность\nby I. I. Dzha
dan as part of Quantum Optics and Related Topics\n\n\nAbstract\nПроан
ализированы особенности передачи инфор
мации через закрытые каналы на основе мн
огофотонной запутанности. Важным преиму
ществом таких каналов является возможно
сть дополнительного шифрования сообщен
ий классическим ключом нумерации канало
в. На примере многоканального квантовог
о транслятора с шифроключом рассмотрена
кажущаяся передача информации "в прошло
е". Показано\, что такое "ретрокаузальное"
действие не приводит к нарушению класси
ческой причинности и находит свои парал
лели в физике и других дисциплинах.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/37/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kh. Sh. Meretukov
DTSTART:20240908T123000Z
DTEND:20240908T130000Z
DTSTAMP:20260404T095423Z
UID:QOART/38
DESCRIPTION:Title: Nonlinear equations in open quantum systems\nby Kh. Sh. Meretuko
v as part of Quantum Optics and Related Topics\n\n\nAbstract\nThis report
presents the kinetic equation for the mean values obtained by the method o
f time-dependent projective operators. This equation is applied to the Ker
r model. For this system\, a closed system of differential equations for t
he averages from the creation and annihilation operators and their squares
is obtained. 2 regimes of the system are considered: without external fie
ld and with small external field. For the 1st regime\, the obtained result
s are compared with analytical results\n
LOCATION:https://stable.researchseminars.org/talk/QOART/38/
END:VEVENT
BEGIN:VEVENT
SUMMARY:D.V. Kupriyanov
DTSTART:20240908T130000Z
DTEND:20240908T134000Z
DTSTAMP:20260404T095423Z
UID:QOART/39
DESCRIPTION:Title: Radiative Coupling of a Multilevel Atom with a Dielectric Structure<
/a>\nby D.V. Kupriyanov as part of Quantum Optics and Related Topics\n\n\n
Abstract\nThe coupling of quantum emitters\, such as cold atoms\, with nan
oscale structures like dielectric waveguides and subwavelength resonators
brings new opportunities for quantum technology. The directional emission
of individual photons could create certain conditions for a quantum comput
er interface based on neutral atoms. Prototypes of similar nanophotonic de
vices have been already demonstrated in experiments involving the confinem
ent of atoms within microresonators\, photonic crystal structures\, and na
nofibers [1]. We propose a microscopic scheme for calculating radiation co
rrections to the energy spectrum of a single-electron atom in the presence
of a nanoscale dielectric object. The calculation takes into account the
complete Zeeman structure of an isolated atomic transition and can be appl
ied to systems with arbitrary geometric configurations. At the studied fre
quencies\, the dielectric properties can be replicated by replacing the bu
lk material with an ensemble of two-level atoms with resonant transition f
requencies being offset from the radiation frequency of a reference atom [
2]. We demonstrate the approach by applying it to various nanostructure ge
ometries used in the experiments [3] and conduct a comparative analysis to
demonstrate the advantages of exciting an atom at frequencies close to th
e edge of the Brillouin zone in asymmetric photonic crystals. Figure 1 dem
onstrates spectral parameters of the caesium-133 atom placed near the one-
dimensional asymmetric photonic crystal. Quasi-energy sublevels exhibit tw
ofold degeneracy and non-orthogonality between states from different energ
y levels\, which we show is connected to the nontrivial axial symmetry in
atomic excitation and decay channels. The observed increase in atomic deca
y rate is accompanied by its directional radiation into a waveguide mode\,
which is significant for developing quantum interfaces based on individua
l atoms and photons. Due\nto this radiation\, a resonant scattering channe
l can be used to create a chain of entangled atoms. The phase of the atomi
c state changes by 180 degrees during the resonant scattering of photons\,
that is a critical aspect of the C-Z entanglement protocol\, a promising
scheme proposed as an alternative to the Rydberg blockade protocol.\n\nAck
nowledgements: The work was funded by the Russian Science Foundation (Proj
ect No. 23-72-10012).\n\nReferences\n\n[1] D E Chang\, J S Douglas\, A Gon
zález-Tudela\, C-L Hung and H J Kimble\, Rev. Mod. Phys. 90\, 031002 (201
8)\n\n[2] N A Moroz\, L V Gerasimov\, A D Manukhova and D V Kupriyanov\, P
hys. Rev. A 109\, 013714 (2024)\n\n[3] N Fayard\, A Bouscal\, J Berroir\,
A Urvoy\, T Ray\, S Mahapatra\, M Kemiche\, J A Levenson\, J-J\nGreffet\,
K Bencheikh\, J Laurat and C Sauvan\, Opt. Express 30\, 45093 (2022)\n
LOCATION:https://stable.researchseminars.org/talk/QOART/39/
END:VEVENT
BEGIN:VEVENT
SUMMARY:I.V. Volovich
DTSTART:20240909T060000Z
DTEND:20240909T073000Z
DTSTAMP:20260404T095423Z
UID:QOART/40
DESCRIPTION:Title: On the Absence of Bell-CHSH Inequality Violations at Large Distances
\nby I.V. Volovich as part of Quantum Optics and Related Topics\n\n\nA
bstract\nThe standard derivation of Bell-type inequality violations is typ
ically applied only to scenarios involving short distances between detecto
rs. This conventional approach often overlooks the dependence of quantum m
echanical wave functions on space-time variables. In this study\, we exami
ne the behavior of entangled photons produced in spontaneous parametric do
wnconversion (SPDC) experiments and demonstrate that Bell-CHSH inequalitie
s are not violated at large distances. We analyze the propagation of entan
gled photon wave packets and show that these initially entangled states te
nd to disentangle over large spacelike separations. This finding aligns wi
th the observed violations of Bell inequalities at shorter detector separa
tions. To further explore this phenomenon\, we propose an experiment to in
vestigate how the quantum correlation function and Bell values change with
increasing detector distance\, predicting that these quantities will decr
ease inversely with distance.\nOn the absence of violation of Bell-CHSH in
equalities at large distances.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/40/
END:VEVENT
BEGIN:VEVENT
SUMMARY:G.N. Goltsman
DTSTART:20240909T074000Z
DTEND:20240909T084000Z
DTSTAMP:20260404T095423Z
UID:QOART/41
DESCRIPTION:Title: Superconducting single photon detector: research and applications\nby G.N. Goltsman as part of Quantum Optics and Related Topics\n\n\nAbst
ract\nDuring last twenty years\, a new generation of superconducting detec
tors based on hot-electron-phenomena was developed. These sensors have alr
eady demonstrated performance that makes them devices-of-choice for many t
erahertz\, infrared and optical applications. The development of compact h
elium-free cryocoolers together with effective sources of terahertz\nand i
nfrared radiation greatly expanded the field of application of superconduc
ting detectors including astronomy\, medicine\, security and quantum commu
nications\, and made them friendly in use. To date\, due to the growing in
terest\, the market for superconducting devices is gradually expanding\, a
s evidenced by the emergence of small companies engaged in the development
\, improvement and commercialization of superconducting devices. \nOne suc
h device is the superconducting nanowire single-photon detector (SNSPD or
SSPD). SNSPDs combine high detection efficiency\, low dark count rate\, an
d high temporal resolution in a single device in visible and near IR range
. SNSPDs have been successfully employed for classical and quantum optics
applications ranging from optical time domain reflectometry (OTDR)\, light
detection and ranging (LiDAR)\, space-to-ground communications\, quantum
dot photonics\, quantum key distribution to experiments with indistinguish
able and entangled photon pairs and applications in the life sciences. \nF
ew years ago\, a fully integrated circuit including a single photon source
(carbon nanotube)\, detectors (SNSPDs) and Si3N4 waveguides has already b
een implemented on a chip. Going beyond such proof-of-principle concepts\,
the realization of large scale QPICs is expected to have profound impact
on science and technology\, material engineering\, as well as quantum info
rmation processing including quantum computing\, simulation and metrology.
\nIt has recently been shown that the nanosize of the current-carrying str
ip is not a necessary attribute for single-photon detection. Using a kinet
ic-equation approach\, the dynamics of electrons and phonons in current-ca
rrying superconducting strip with a current close to the depairing current
after the absorption of a single photon of the near-infrared or optical r
ange was studied. Second\, it has been experimentally demonstrated that si
ngle-photon detection is indeed achieved in micrometer-wide NbN bridges bi
ased by a direct current close to the experimental critical current\, whic
h is estimated to be at least 50% of the theoretically expected depairing
current. These results offer an alternative to the standard superconductin
g single-photon detectors\, based on nanometer-scale nanowires implemented
in a long meandering structure. The results are consistent with improved
theoretical modeling based on the theory of nonequilibrium superconductivi
ty\, including the vortex-assisted mechanism of initial dissipation. To th
ink about practical devices\, we choose to work with wide wires fabricated
with photolithography rather than narrower wires commonly fabricated with
e-beam lithography. These wider wires consume more area\, which is proble
matic in large integrated systems. We find that elimination of even a\nsin
gle e-beam lithography step greatly simplifies fabrication process. \nFurt
her development of SSPDs associated with the implementation of complex int
egrated photonic (PICs) and quantum photonic integrated circuits (QPICs) o
n a single chip. Integrated circuits are resistant to mechanical vibration
s and temperature fluctuations\, they do not require long alignment proced
ure and can be easily scaled. To date\, integrated SNSPDs have been implem
ented on various material platforms\, such as silicon on insulator (SOI)\,
gallium arsenide (GaAs)\, silicon nitride (Si3N4) and polycrystalline dia
mond. Each platform has its advantages and disadvantages\, so further deve
lopment takes place in parallel. Despite the fact that all the building bl
ocks for a fully-functional QPIC\, including single-photon sources\, detec
tors and passive circuits\, have been demonstrated\, full integration of a
ll the components on a single chip is still a somewhat challenging and com
plicated task.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/41/
END:VEVENT
BEGIN:VEVENT
SUMMARY:E.O. Kiktenko
DTSTART:20240909T092000Z
DTEND:20240909T110000Z
DTSTAMP:20260404T095423Z
UID:QOART/42
DESCRIPTION:Title: Quantum computing with qudits\nby E.O. Kiktenko as part of Quant
um Optics and Related Topics\n\n\nAbstract\nRecent progress in a developme
nt of quantum computing platforms operating with qudits (d-dimensional qua
ntum particles with d>2) rises important questions of how such platforms c
an be used in the most efficient way for implementing known quantum algori
thms. In my presentation\, I will be discussing possible approaches for th
e implementation of qubit-based circuits using qudit-based hardware. These
approaches include: (i) employing higher-level qudits to substitute ancil
lary qubits in the decomposition of multiqubit gates\, (ii) embedding the
computational space of multiple qubits into a single qudit\, and (iii) com
bining approaches (i) and (ii). Special attention will be paid to the poss
ible experimental implementation of the discussed approaches within the sy
stems of superconducting qubits and trapped ion qudits.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/42/
END:VEVENT
BEGIN:VEVENT
SUMMARY:G.G. Amosov
DTSTART:20240909T120000Z
DTEND:20240909T130000Z
DTSTAMP:20260404T095423Z
UID:QOART/43
DESCRIPTION:Title: On a generalized approach to quantum tomography via projective unita
ry representations of groups\nby G.G. Amosov as part of Quantum Optics
and Related Topics\n\n\nAbstract\nSuppose that $\\mathfrak {M}$ is a posi
tive operator-valued measure on a measurable space $X$ with values in the
set of all positive bounded operators\n$B(H)_+$ in a separable Hilbert spa
ce $H$. If $g\\to U_g$ is a projective unitary representation of a group $
G$ in $H$ and one can define an action of $G$\non $X$ by the rule $x\\in X
\\to gx\\in X\,\\ g\\in G$\, then $\\mathfrak M$ is said to be covariant
with respect to $\\mathcal {U}=\\{U_g\,\\ g\\in G\\}$ under the condition
$U_g\\mathcal {M}(B)U_g^*=\\mathfrak {M}(gB)$ for all measurable subsets $
B\\subset X$ and $g\\in G$. In quantum tomography theory we use a set of f
unctions instead of a density operator $\\rho $. Using a covariant POVM $\
\mathfrak M$ equipped with a projective unitary representation $\\mathcal
U$ we can determines two possible functions of this kind. One is $f_{\\rho
}(g)=Tr(\\rho U_g)$ and the other is $F_{\\rho }(B)=Tr(\\rho \\mathfrak {M
}(B))$. The first function can be named a characteristic function of $\\rh
o $\, while the second one is associated with a measurement of $\\rho $ by
$\\mathfrak {M}$. We attribute these two functions to homodyne and hetero
dyne measurements and discuss the connection between them.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/43/
END:VEVENT
BEGIN:VEVENT
SUMMARY:V.V. Dodonov
DTSTART:20240909T134000Z
DTEND:20240909T151000Z
DTSTAMP:20260404T095423Z
UID:QOART/44
DESCRIPTION:Title: Quantum dynamics of oscillator-like systems when some parameters cha
nge signs\nby V.V. Dodonov as part of Quantum Optics and Related Topic
s\n\n\nAbstract\nI shall talk about some recent results concerning the evo
lution of a quantum particle in time-dependent oscillator-like potentials\
, when the frequency or its square change the sign. The main attention is
given to the limit cases of adiabatic and fast evolutions. Applications to
a charged particle in time-dependent magnetic fields will be discussed\,
as well.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/44/
END:VEVENT
BEGIN:VEVENT
SUMMARY:S.L. Bala
DTSTART:20240910T060000Z
DTEND:20240910T070000Z
DTSTAMP:20260404T095423Z
UID:QOART/45
DESCRIPTION:Title: Reading-off properties about the quantized radiation field from the
optical tomogram\nby S.L. Bala as part of Quantum Optics and Related T
opics\n\n\nAbstract\nOptical tomograms are readily obtained from experimen
tal data. The tomogram is the starting point for reconstructing the densit
y operator or Wigner function. The reconstruction program is often challen
ging\, particularly in the case of systems with infinite dimensional Hilbe
rt spaces\, as for instance in optics. It is therefore well-advised to ext
ract as many properties of the radiation field as possible directly from t
he tomogram avoiding detailed state reconstruction. The importance of opti
cal tomograms\, and the fact that they contain all the information about t
he quantized radiation field have been highlighted in detail by different
research groups\, primarily from Russia. We will expand on this aspect and
identify certain nonclassical properties of states of light directly from
qualitative features of appropriate optical tomograms\, and also quantify
these properties.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/45/
END:VEVENT
BEGIN:VEVENT
SUMMARY:K. Thapliyal
DTSTART:20240910T074000Z
DTEND:20240910T091000Z
DTSTAMP:20260404T095423Z
UID:QOART/46
DESCRIPTION:Title: Quantum state engineering of multi-mode and entangled optical fields
using photon counting\nby K. Thapliyal as part of Quantum Optics and
Related Topics\n\n\nAbstract\nNonclassical states\, having negative Glaube
r-Sudarshan P-function\, do not have a classical analogue.\nThese states h
ave paved way for second quantum revolution and photonic quantum technolog
y. A few\nexamples of generation of such states in nonlinear optical proce
sses and its challenges will be\ndiscussed. Photon number measurements and
post-selection make a plethora of quantum state\nengineering operations f
easible. Quantum state engineering using non-Gaussian operations provides\
npowerful tool for continuous variable quantum information. Practical chal
lenges in their\nimplementation and feasibility of generation of such stat
es will be discussed [1-4]. Twin beams are\ngenerated in a nonlinear optic
al process\, namely spontaneous parametric down conversion\, under\nstrong
er pumping. They are endowed with ideally perfect photon number correlatio
ns in the\nconstituting signal and idler beams. This quantum feature is re
vealed by the sub-shot noise photon\nnumber correlations. However\, the ma
rginal signal and idler photon number distributions are\nmultimode thermal
. We illustrate the generation of engineered multimode quantum states from
twin\nbeams by photon subtraction and addition with supporting experiment
al realization. Future prospects\,\nin view of our results\, will be discu
ssed.\n\n[1] K. Thapliyal\, J. Peřina Jr.\, O. Haderka\, V. Michálek\, a
nd R. Machulka\, Experimental characterization of\nmultimode photon-subtra
cted twin beams\, Phys. Rev. Res. 6\, 013065 (2024).\n\n[2] J. Peřina Jr.
\, K. Thapliyal\, O. Haderka\, V. Michálek\, and R. Machulka\, Generalize
d sub-Poissonian states of\ntwo-beam fields\, Opt. Express 32\, 537 (2024)
.\n\n[3] K. Thapliyal\, J. Peřina Jr.\, O. Haderka\, V. Michálek\, and R
. Machulka\, Experimental photon addition and\nsubtraction in multi-mode a
nd entangled optical fields\, Opt. Lett. 49\, 4521 (2024).\n\n[4] J. Peři
na Jr.\, K. Thapliyal\, O. Haderka\, V. Michálek\, and R. Machulka\, Sub-
Poissonian twin beams\, Optica\nQuantum 2\, 148 (2024).\n
LOCATION:https://stable.researchseminars.org/talk/QOART/46/
END:VEVENT
BEGIN:VEVENT
SUMMARY:P.R. Sharapova
DTSTART:20240910T092000Z
DTEND:20240910T102000Z
DTSTAMP:20260404T095423Z
UID:QOART/47
DESCRIPTION:Title: Multimode squeezing: generation and characterization\nby P.R. Sh
arapova as part of Quantum Optics and Related Topics\n\n\nAbstract\nMultim
ode squeezed light is an increasingly popular tool in photonic quantum tec
hnologies\, including sensing\, imaging\, and computing [1]. In metrology\
, it provides the measurement of the phase beyond the classical sensitivit
y limit [2\,3]\, its role was crucial for the first observation of gravita
tional waves [4]. At the same time\, multiple squeezed modes are promising
tools for continuous-variable quantum computing\, quantum information pro
cessing and quantum communication\, where each mode (qumode) serves as an
information carrier and a large set of modes can be used for the cluster s
ates generation and measurement-based quantum computation [5].\nWith numer
ous applications of multimode squeezed light\, it is important to characte
rize squeezing in multiple spatial and temporal modes taking into account
internal losses in the system: \nWhen PDC is generated in transparent bulk
nonlinear crystals the absorption is small enough to be neglected\, howev
er\, internal losses can be significant for structured media like waveguid
es\, where the guided light can be lost due to scattering from surface rou
ghness.\nWe investigate the mode structure of lossy broadband multimode sq
ueezed light and show how the maximal possible squeezing can be extracted
and measured. In opposite to an ideal multimode squeezed states\, where th
e unique basis of Schmidt modes can be found via Bloch-Messiah reduction o
f Bogoliubov transformation [6]\, the broadband basis of Schmidt modes for
lossy squeezed states cannot be uniquely defined. We introduce a new type
of broadband basis for lossy systems in which the squeezing is maximized\
, i.e.\, the upper bound for squeezing is reached\, and show how these mod
es can be constructed [7].\nFurthermore\, the existing experimental method
s of multimode squeezed vacuum characterization (homodyne detection\, proj
ective filtering) are technically complicated\, and in the best case\,\nde
al with a single mode at a time. We present a method [8] based on a cascad
ed system of nonlinear crystals to simultaneously measure squeezing in dif
ferent spatial modes. In such a system\, the second crystal serves as an a
mplifier/deamplifier for the squeezed light generated in the first crystal
(squeezer). The direct intensity measurement of light after the amplifier
allows us to reconstruct the squeezing of the light generated in the firs
t crystal.\n\n[1] U. L. Andersen\, T. Gehring\, C. Marquardt\, and G. Leuc
hs\, Phys. Scr. 91 053001 (2016).\n\n[2] V. Giovannetti\, S. Lloyd\, and L
. Maccone\, Science 306\, 1330-1336 (2004).\n\n[3] D. Scharwald\, T. Meier
\, P. R. Sharapova\, Phys. Rev. Research 5\, 043158 (2023).\n\n[4] B.P. Ab
bott et al. (LIGO Scientific Collab. and Virgo Collab.)\, Phys. Rev. Lett.
119\, 161101 (2017).\n\n[5] M. V. Larsen\, X. Guo\, C. R. Breum\, J. S. N
eergaard-Nielsen\, U. L. Andersen\, Science 366\, 6463 (2018).\n\n[6] M. G
. Raymer and I. A. Walmsley\, Phys. Scripta 95\, 064002 (2020).\n\n[7] D.
A. Kopylov\, T. Meier\, P. R. Sharapova\, arXiv:2403.05259 (2024).\n\n[8]
I. Barakat\, M. Kalash\, D. Scharwald\, P. R. Sharapova\, N. Lindlein\, M.
V. Chekhova\, arXiv:2402.15786 (2024).\n
LOCATION:https://stable.researchseminars.org/talk/QOART/47/
END:VEVENT
BEGIN:VEVENT
SUMMARY:I.V. Ermakov
DTSTART:20240910T120000Z
DTEND:20240910T133000Z
DTSTAMP:20260404T095423Z
UID:QOART/48
DESCRIPTION:Title: Polynomially restricted operator growth in dynamically integrable mo
dels\nby I.V. Ermakov as part of Quantum Optics and Related Topics\n\n
\nAbstract\nWe provide a framework to determine the upper bound to the com
plexity of a computing a given observable with respect to a Hamiltonian. B
y considering the Heisenberg evolution of the observable\, we show that ea
ch Hamiltonian defines an equivalence relation\, causing the operator spac
e to be partitioned into equivalence classes. Any operator within a specif
ic class never leaves its equivalence class during the evolution. We provi
de a method to determine the dimension of the equivalence classes and eval
uate it for various models\, such as the XY chain and Kitaev model on tree
s. Our findings reveal that the complexity of operator evolution in the XY
model grows from the edge to the bulk\, which is physically manifested as
suppressed relaxation of qubits near the boundary. Our methods are used t
o reveal several new cases of simulable quantum dynamics\, including a XY-
ZZ model which cannot be reduced to free fermions.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/48/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.N. Pechen
DTSTART:20240910T134000Z
DTEND:20240910T151000Z
DTSTAMP:20260404T095423Z
UID:QOART/49
DESCRIPTION:Title: Phenomenon of a stronger trapping behaviour in $\\Lambda$-type quant
um systems and quantum control landscapes\nby A.N. Pechen as part of Q
uantum Optics and Related Topics\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/QOART/49/
END:VEVENT
BEGIN:VEVENT
SUMMARY:R.-K. Lee
DTSTART:20240911T060000Z
DTEND:20240911T073000Z
DTSTAMP:20260404T095423Z
UID:QOART/50
DESCRIPTION:Title: Machine-learning enhanced quantum state tomography and its applicati
ons for optical cat states\nby R.-K. Lee as part of Quantum Optics and
Related Topics\n\n\nAbstract\nWith this talk\, I will first illustrate th
e implementation of our machine-learning (ML) enhanced quantum state tomog
raphy (QST) for continuous variables\, through the experimentally measured
data generated from squeezed vacuum states [1]\, as an example of quantum
machine learning [2]. Our recent progress will be demonstrated in applyin
g such a ML-QST on Wigner currents [3]\, single-photon Fock state [4]\, op
tical cat state [5]\, Bayesian estimation for gravitational wave detector
s [6\, 7]\, and quantumness measure [8].\n\n[1] Hsien-Yi Hsieh\, et al.\,
"Extract the Degradation Information in Squeezed States with Machine Learn
ing\," Phys. Rev. Lett. 128\, 073604 (2022).\n\n[2] Alexey Melnikov\, Moh
ammad Kordzanganeh\, Alexander Alodjants\, and RKL\," Quantum Machine Lear
ning: from physics to software engineering\," Adv. in Phys. X (Review Arti
cle) 8\, 2165452 (2023).\n\n[3] Yi-Ru Chen\, et al.\, "Experimental recons
truction of Wigner phase-space current\," Phys. Rev. A 108\, 023729 (2023)
.\n\n[4] Hsien-Yi Hsieh\, et al.\, "Neural network enhanced single-photon
Fock state tomography\," revised to Phys. Rev. A (2024)\; [arXiv: 2405.02
812].\n\n[5] Yi-Ru Chen\, et al.\, "Generation of heralded optical `Schroe
dinger cat' states by photon-addition\," Phys. Rev. A 110\, 023703 (2024).
\n\n[6] Hsien-Yi Hsieh\, et al.\, in preparation for publication (2024).\n
\n[7] Yuhang Zhao\, et al.\, "Frequency-dependent squeezed vacuum source f
or broadband quantum noise reduction in advanced gravitational-wave detect
ors\," Phys. Rev. Lett. 124\, 171101 (2020)\; Editors' Suggestion\; Feat
ured in Physics.\n\n[8] Ole Steuernagel and RKL\, "Quantumness Measure fro
m Phase Space Distributions\," [arXiv: 2311.17399].\n
LOCATION:https://stable.researchseminars.org/talk/QOART/50/
END:VEVENT
BEGIN:VEVENT
SUMMARY:D.B. Yusupov
DTSTART:20240911T074000Z
DTEND:20240911T081000Z
DTSTAMP:20260404T095423Z
UID:QOART/51
DESCRIPTION:Title: Quasi-Phase Matching in Nonlinear Optics\nby D.B. Yusupov as par
t of Quantum Optics and Related Topics\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/QOART/51/
END:VEVENT
BEGIN:VEVENT
SUMMARY:S.A. Moiseev
DTSTART:20240911T081000Z
DTEND:20240911T091000Z
DTSTAMP:20260404T095423Z
UID:QOART/52
DESCRIPTION:Title: Photon echo protocols of optical quantum memory\nby S.A. Moiseev
as part of Quantum Optics and Related Topics\n\n\nAbstract\nThe main prop
erties of the conventional photon echo quantum memory protocols are analyz
ed and the results of recent experiments are discussed. The distinctive f
eatures of the effect of spectral dispersion and nonlinear interaction of
light pulses with resonant atoms on the quantum storage of broadband signa
l pulses in the studied echo protocols are identified and discussed. Usin
g the photon echo area theorem\, closed analytical solutions for quantum m
emory echo protocols are obtained\, describing the storage of weak and int
ense signal pulses\, allowing us to find conditions for the implementation
of high efficiency in echo protocols with strong nonlinear interaction of
signal and control pulses with atoms. The key existing practical problems
and ways to solve them in realistic experimental conditions are described
. Finally\, new optical quantum memory protocols based on the use of long-
lived macroscopic quantum coherence are also proposed and their advantages
are discussed.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/52/
END:VEVENT
BEGIN:VEVENT
SUMMARY:O.V. Man'ko
DTSTART:20240911T092000Z
DTEND:20240911T110000Z
DTSTAMP:20260404T095423Z
UID:QOART/53
DESCRIPTION:Title: Probability representation for quantum states on examples of oscilla
tor and qubit\nby O.V. Man'ko as part of Quantum Optics and Related To
pics\n\n\nAbstract\nIn conventional formulation of quantum mechanics syste
m states are described by wave functions\, density operators and their rep
resentations as the Wigner function\, the Husimi function\, the Glauber-Su
darshan function. Many decades (practically century) the idea to construct
usual probability distributions to describe the states of quantum systems
was not realized. Only recently such probability distribution representat
ion for quantum states was constructed for all systems. The spin (qudit) s
tates are described by conditional probability distribution w(X|j) and osc
illator states are described by quantum tomograms (symplectic tomographic
probability distribution function). In the talk explicit expressions for t
hese probabilities are given. The tomograms describing oscillator states a
re given by Gaussian probability distributions which contain all informati
on about usual wave functions of the states and density matrices of the st
ate. Two qubit states are described by conditional probabilities and usual
density matrices of quantum states are expressed in terms of these probab
ilities. The Schrödinger equation for wave function is mapped onto kineti
c equation for the introduced probability distributions. The general appro
ach for quantization based on the formalism of star-product of functions-s
ymbols of operators is reviewed.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/53/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.S. Trushechkin
DTSTART:20240911T120000Z
DTEND:20240911T133000Z
DTSTAMP:20260404T095423Z
UID:QOART/54
DESCRIPTION:Title: Quantum communication networks with bipartite entanglement sources\nby A.S. Trushechkin as part of Quantum Optics and Related Topics\n\n\n
Abstract\nQuantum networks attract much interest now. One of obvious purpo
ses of quantum networks is secure communications. The usual quantum key di
stribution (QKD) deals with bipartite communication\, but scaling of QKD t
o network solutions is developed now. In the first part of the talk\, we w
ill consider networks of users connected by bipartite QKD links. Such netw
orks already exist. A problem arises: Having a network of bipartite QKD li
nks\, how to generate a conference key at maximal rate? An optimal solutio
n is given by a spanning-tree-packing protocol for conference key propagat
ion.\n\nThe second part of the talk will be devoted to foreseeable future
quantum networks with bipartite entanglement sources. Such networks provid
e more possibilities and problems to be considered. The problem of confere
nce key distribution is still relevant for these networks (but with more p
ossibilities). A fully quantum counterpart of this problem is the Greenber
ger-Horne-Zeilinger (GHZ) multipartite entangled state distillation. GHZ s
tates find many cryptographic\, metrologic and computational applications.
Spanning tree packing protocol also can be used for GHZ distillation and
is also optimal whenever the distributed bipartite entangled states are pu
re. For general (mixed) bipartite quantum states\, we present fundamental
bounds on the conference key distribution and GHZ distillation rates for s
uch networks.\n
LOCATION:https://stable.researchseminars.org/talk/QOART/54/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.V. Sergienko
DTSTART:20240911T134000Z
DTEND:20240911T151000Z
DTSTAMP:20260404T095423Z
UID:QOART/55
DESCRIPTION:Title: Directionally unbiased linear optics enable novel high-resolution se
nsors and quantum network routers\nby A.V. Sergienko as part of Quantu
m Optics and Related Topics\n\n\nAbstract\nGrover multiports are higher-di
mensional generalizations of beam splitters in which inputs to any of the
four ports have an equal probability of exiting at any of the four ports\,
including the input port. This offers direct access to a greater number o
f degrees of freedom [1]: We demonstrate that traditional interferometers
can obtain novel features when directionally unbiased multi-ports replace
traditional beam splitters. It will be shown that the Grover-based counter
part of the conventional Michelson interferometer can substantially enhanc
e the phase measurement resolution.\nThe Grover-Michelson interferometer d
emonstrates a tunable intensity-phase slope instead of a traditional fixed
cos2 profile\, thus enabling super-resolution phase measurement while uti
lizing only linear optical elements and classical states of light [2].\nTh
e traditional two-photon Hong-Ou-Mandel (HOM) effect could be expanded ont
o a higherdimensional set of four spatial modes when combining the Grover
coin with quantum-correlated twophoton input and coincidence measurements.
We introduce a novel quantum photonic state router design that allows con
trollable redistribution (switching) of (|2\,0>+|0\,2>) quantum states ove
r these four modes using directionally unbiased linear-optical four-ports
without post-selection [3]. The original HOM effect only enables photon pa
irs to exit in two directions in space. However\, when beam splitters and
phase shifters accompany the Grover coin\, the result is a directionally c
ontrollable two-photon HOM effect in four spatial modes\, with the outgoin
g photon direction controlled by changing the phases in the system. By thi
s means\, spatial and temporal control of the propagation of the two-photo
n superposition state through a network or quantum nodes (quantum state ro
uting) can be achieved.\n\n[1] Shuto Osawa\, David S. Simon\, and Alexande
r V. Sergienko "Directionally-Unbiased Unitary Optical Devices in Discrete
-Time Quantum Walks\,” Entropy\, v. 21\, p. 853 (2019).\n\n[2] Christoph
er R. Schwarze\, David S. Simon\, and Alexander V. Sergienko\,'' Enhanced-
Sensitivity Interferometry With Phase-Sensitive Unbiased Multiports\,” P
hys. Rev. A 107\, 052615 (2023)\n\n[3] Shuto Osawa\, David S. Simon\, and
Alexander V. Sergienko "Higher-Dimensional Hong-Ou-Mandel Effect and State
Redistribution With Linear-Optical Multiports\,” Phys. Rev. A 102\, 063
712 (2020).\n
LOCATION:https://stable.researchseminars.org/talk/QOART/55/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.L. Sokolov
DTSTART:20240909T152000Z
DTEND:20240909T162000Z
DTSTAMP:20260404T095423Z
UID:QOART/56
DESCRIPTION:Title: Пучки с осесимметричной поляризацио
нной структурой\nby A.L. Sokolov as part of Quantum Opti
cs and Related Topics\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/QOART/56/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. E. Teretenkov
DTSTART:20240911T152000Z
DTEND:20240911T153000Z
DTSTAMP:20260404T095423Z
UID:QOART/57
DESCRIPTION:Title: Closing\nby A. E. Teretenkov as part of Quantum Optics and Relat
ed Topics\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/QOART/57/
END:VEVENT
END:VCALENDAR