BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:A. V. Andrianov DTSTART:20241203T130000Z DTEND:20241203T140000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/1 DESCRIPTION:Title: Polarization squeezing in chalcogenide fibers\nby A. V. An drianov as part of Seminar on Quantum Optics and Related Topics\n\n\nAbstr act\nWe experimentally demonstrate the generation of polarization-squeezed light in a short piece of solid-core chalcogenide (ChG) (As2S3) fiber via the Kerr effect for femtosecond pulses at 1.56μm. Directly measured sque ezing of −2.8 dB is obtained in a setup without active stabilization. Nu merical simulations are in good agreement with the experimental results an d indicate that the measured squeezing in our setup is mainly limited by t he losses in the detection system rather than by the fiber properties.\n\n The talk is based on the paper “Polarization squeezing in chalcogenide f ibers” published in Optics Letters 2024.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/1/ END:VEVENT BEGIN:VEVENT SUMMARY:A. A. Gaidash DTSTART:20241218T130000Z DTEND:20241218T140000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/2 DESCRIPTION:Title: Algebraic approach to dynamics of open multimode bosonic syste ms\nby A. A. Gaidash as part of Seminar on Quantum Optics and Related Topics\n\n\nAbstract\nQuantum dynamics of open continuous variable systems is a multifaceted\, rapidly evolving field of both fundamental and techno logical significance. An important example is a multimode photonic system coupled to a Markovian bath (the environmental correlation times are short er than the system's relaxation or\ndecoherence time) so that the density matrix dynamics is governed by the master equation of the Lindblad form. Using currently available methods\, theoretical analysis of the Lindblad d ynamics complicated by intermode couplings can be rather involved even for exactly soluble models. The algebraic approach suggested in this paper si mplifies both quantitative and qualitative analysis of the intermode-coupl ing-induced effects in multimode systems by reducing the Lindblad equation to the form determined by the effective Hamiltonian. Specifically\, we de velop the algebraic method based on the Lie algebra of quadratic combinati ons of left and right superoperators associated with matrices to study the Lindblad dynamics of multimode bosonic systems coupled with a thermal bat h and described by the Liouvillian superoperator that takes into account b oth dynamical (coherent) and environment mediated (incoherent) interaction s between the modes. Our algebraic technique is applied to transform the L iouvillian into the diagonalized form by eliminating jump superoperators a nd solve the spectral problem. The temperature independent effective non-H ermitian Hamiltonian\, $\\hat{H}_{\\ind{eff}}$\, is found to govern both the diagonalized Liouvillian and the spectral properties. It is shown that the Liouvillian exceptional points are represented by the points in the p arameter space where the matrix\, $H$\, associated with $\\hat{H}_{\\ind{ eff}}$ is non-diagonalizable. We use our method to derive the low-tempera ture approximation for the superpropagator and to study the special case o f a two mode system representing the photonic polarization modes\,e.g. opt ical polarization qubit.For this system\, we describe the geometry of exce ptional points in the space of frequency and relaxation vectors parameteri zing the intermode couplings and\, for a single-photon state\, evaluate th e time dependence of the density matrix.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/2/ END:VEVENT BEGIN:VEVENT SUMMARY:B. A. Malomed DTSTART:20250109T130000Z DTEND:20250109T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/3 DESCRIPTION:Title: Trapping wave fields in an expulsive potential by means of lin ear coupling\nby B. A. Malomed as part of Seminar on Quantum Optics an d Related Topics\n\n\nAbstract\nWe demonstrate the existence of confined s tates in one- and two-dimensional (1D and 2D) systems of two linearly-coup led components\, with the confining harmonic-oscillator (HO) potential act ing upon one-component\, and an expulsive anti -HO potential acting upon t he other. The systems can be implemented in optical and BEC dual-core wave guides. In the 1D linear system\, codimension-one solutions are found in a n exact form for the ground state (GS) and dipole mode (the first excited state). Generic solutions are produced by the variational approximation\, and are found in a numerical form. Exact codimension-one solutions and gen eric numerical ones are obtained for the GS and vortex states in the 2D sy stem. Both the trapped and anti-trapped components of the bound states may be dominant ones\, in terms of the norm. The localized modes may be categ orized as bound states in continuum\, as they coexist with delocalized one s. The1D states\, as well as the GS in 2D\, are weakly affected and remain stable if the self-attractive or repulsive nonlinearity is added to the s ystem. The self-attraction makes the vortex states unstable against splitt ing\, while they remain stable under the action of the self-repulsion.\n\n Publications: N. Hacker and B. A. Malomed\, Nonlinear dynamics of wave pac kets in tunnel-coupled harmonic-oscillator traps\, Symmetry 13\, 372 (2021 )\; Trapping wave fields in an expulsive potential by means of linear coup ling\, Phys. Rev. E 105\, 034213 (2022).\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/3/ END:VEVENT BEGIN:VEVENT SUMMARY:A. Z. Khoury (Universidade Federal Fluminense) DTSTART:20250121T130000Z DTEND:20250121T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/4 DESCRIPTION:Title: Recognition of Light Orbital-Angular-Momentum Superpositions f or Quantum Communication\nby A. Z. Khoury (Universidade Federal Flumin ense) as part of Seminar on Quantum Optics and Related Topics\n\n\nAbstrac t\nWe study the tomography of spatial qudits encoded on structured light p hotons in the space of fixed order transverse modes. While direct position measurements with cameras do not provide an informationally complete Posi tive Operator Valued Measure (POVM)\, this property is achieved with the u se of astigmatic transformation\, allowing full characterization of the sp atial quantum state from simple intensity measurements in both the intense and in the low photocount regimes. These methods are useful for classical and quantum communication with structured light and will be tested in a q uantum network being set up in the Rio de Janeiro metropolitan area.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/4/ END:VEVENT BEGIN:VEVENT SUMMARY:A. D. Kiselev DTSTART:20250206T130000Z DTEND:20250206T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/5 DESCRIPTION:Title: Lindblad dynamics of multi-mode photonic systems: Exceptional points and speed of evolution\nby A. D. Kiselev as part of Seminar on Quantum Optics and Related Topics\n\n\nAbstract\nThis talk deals with inte rmode-interaction-induced effects in dynamics of open multi-mode photonic systems representing a family of continuous variable systems whose density matrix dynamics is governed by the master equation of the Lindblad form ( the so-called Gorini-Kossakowski-Sudarshan-Lindblad master equation). We b riefly discuss two analytical techniques to perform theoretical analysis o f the Lindblad dynamics complicated by intermode couplings: (a) an algebra ic approach based on the algebra of bilinear superoperators recently sugge sted in [Gaidash et al.\, arXiv:2412.13890[quant-phys]] and (b) the method of characteristic functions. We employ exact solution of the thermal bath Lindblad master equation with the Liouvillian superoperator that takes in to account both dynamic (coherent) and environment induced (incoherent) in termode couplings to study the speed of evolution and the quantum speed li mit (QSL) times of an open multi-mode bosonic system. For Gaussian states\ , we derive explicit expressions for the evolution speed and the QSL times . General analytical results are applied to the special case of a two-mode system where the intermode couplings can be parametrized using the two in termode coupling vectors: the frequency vector and the relaxation rate vec tor. For this system\, we describe the geometry of Liouvillian exceptional points in the space of these vectors and present a number of numerical re sults on evolution of Gaussian (two-mode squeezed states) and non-Gaussian (polarization qubit states) states.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/5/ END:VEVENT BEGIN:VEVENT SUMMARY:J. E. Gough DTSTART:20250213T130000Z DTEND:20250213T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/6 DESCRIPTION:Title: Non-Markovian Quantum Stochastic Models\nby J. E. Gough as part of Seminar on Quantum Optics and Related Topics\n\n\nAbstract\nWe gi ve a derivation of the non-Markovian quantum state diffusion equation of D iósi and Strunz starting from a model of a quantum mechanical system coup led to a bosonic bath. We show that the complex trajectories arises as a c onsequence of using the Bargmann-Segal (complex wave) representation of th e bath. In particular\, we construct a reproducing kernel Hilbert space fo r the bath auto-correlation and realize the space of complex trajectories as a Hilbert subspace. The reproducing kernel naturally arises from a feat ure space where the underlying feature space is the one-particle Hilbert s pace of the bath quanta. We exploit this to derive the unravelling of the open quantum system dynamics and show equivalence to the equation of Diós i and Strunz. We also give an explicit expression for the reduced dynamics of a two-level system coupled to the bath via a Jaynes-Cummings interacti on and show that this does indeed correspond to an exact solution of the D iósi-Strunz equation. Finally\, we discuss the physical interpretation of the complex trajectories and show that they are intrinsically unobservabl e.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/6/ END:VEVENT BEGIN:VEVENT SUMMARY:P. Shukla DTSTART:20250216T130000Z DTEND:20250216T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/7 DESCRIPTION:Title: Entanglement dynamics of many body quantum states with evolvin g system conditions\nby P. Shukla as part of Seminar on Quantum Optics and Related Topics\n\n\nAbstract\nThe entanglement analysis of a pure sta te of a many body quantum system requires a prior information about its de nsity matrix/ state matrix\, obtained in principle by solving the Hamilton ian matrix. The missing information due to complexity of the many body int eractions however renders it necessary to consider an ensemble of Hamilton ians and thereby an ensemble for each eigenstate. This in turn leaves a st atistical description of the entanglement measures as the only option. For an ensemble to appropriately represent a many body Hamiltonian\, the ense mble parameters must be determined from the system parameters. A variation of the latter is therefore expected to manifest in variation of the the e nsemble for each eigenstate and thereby their entanglement aspects. We the oretically analyze the effect of varying system conditions on the eigensta tes of a wide range of Hamiltonians and derive a common mathematical formu lation for the bipartite entanglement statistics. As the system informatio n in the formulation enters through a single functional of the ensemble pa rameters\, this implies the analogy of statistics for different eigenstate ensembles (non-Haar type) if they share the same complexity parameter and thereby reveals a deep web of connection underlying among quantum states of different Hamiltonians (with same global symmetry class). Besides revea ling universality among non-haar states\, the information is also relevant for quantum state engineering e.g. how to achieve a near Haar random stat e starting from a random non-ergodic state.\n\nWork done in collaboration with my PhD student Devanshu Sekhar.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/7/ END:VEVENT BEGIN:VEVENT SUMMARY:S.P. Vyatchanin DTSTART:20250220T130000Z DTEND:20250220T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/8 DESCRIPTION:Title: Broadband variational measurement of a classical force using s trongly nondegenerate dichromatic optical pump\nby S.P. Vyatchanin as part of Seminar on Quantum Optics and Related Topics\n\n\nAbstract\nMaxima l sensitivity of classical force detectors utilizing nonlinear opto-mechan ical transducers is generally de\nfined by the standard quantum limit res ulting from the contamination of the detected signal with noncommuting\nqu antum noises. This restriction can be circumvented by the optimal detectio n protocols. We here show theoretically that interrogating a resonant opto -mechanical displacement transducer with a strongly nondegenerate dichroma tic optical probe enables a quantum back-action evading measurement of a c lassical force acting on the mechanical oscillator being a part of the opt o-mechanical transducer.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/8/ END:VEVENT BEGIN:VEVENT SUMMARY:D. I. Salykina DTSTART:20250227T130000Z DTEND:20250227T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/9 DESCRIPTION:Title: Intracavity squeezing as a tool for improving the quantum nond emolition (QND) measurement scheme\nby D. I. Salykina as part of Semin ar on Quantum Optics and Related Topics\n\n\nAbstract\nWe consider the sch eme of quantum nondemolition measurement of optical quanta based on the Ke rr nonlinearity in an optical microresonator. We demonstrate that by using the intracavity squeezing of a probe beam it is possible to cancel the in terfering effect of self-phase modulation. This results in improvement of scheme sensitivity\, allowing it theoretically to approach the single-phot on sensitivity. Our estimates show that generation and verification of bri ght non-Gaussian quantum states with mean photon numbers up to 1000 is fea sible.\n\nPublications:\n\nBalybin S.\, Salykina D.\, Khalili F. Ya. (2023 ). Improving the sensitivity of Kerr quantum nondemolition measurement via squeezed light. Physical Review A\, 108(5)\, 053708.\n\nSalykina D.\, Bal ybin S.\, Khalili F. Ya. (2025). Intracavity squeezing for a Kerr quantum nondemolition measurement scheme. Physical Review A\, 111(1)\, 013715.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/9/ END:VEVENT BEGIN:VEVENT SUMMARY:E. A. Anashkina DTSTART:20250312T130000Z DTEND:20250312T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/10 DESCRIPTION:Title: Symmetry breaking of counterpropagating Raman waves in optica l microresonators: unexpected findings\nby E. A. Anashkina as part of Seminar on Quantum Optics and Related Topics\n\n\nAbstract\nRecently\, sym metry breaking and related issues in high-Q nonlinear optical microresonat ors have been of growing interest for fundamental research and photonic de vice development. Most studies employ Kerr nonlinearity\, but this is not the only way. We present our recent results on symmetry breaking of counte rpropagating Raman waves at Stokes frequencies in a bidirectionally pumped silica microresonator. We experimentally demonstrate symmetry-broken Rama n lasing with previously unreported features such as intensity switching o f counterpropagating waves and symmetry restoring during pump frequency sw eeping. Symmetric and asymmetric stationary states have been found theoret ically\, but asymmetric states after a pitchfork bifurcation have proven t o be unstable. Such behavior is surprising\, since in the case of pure Ker r nonlinearity (without stimulated Raman scattering)\, a pair of stable as ymmetric states is born after a pitchfork bifurcation\, and the symmetric solution becomes unstable. The explanation of our experimental findings is based on a weak asymmetry in the scheme\, which dramatically changes the dynamic behavior of the system. This is confirmed by numerical simulations with added back reflection for a single Raman wave.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/10/ END:VEVENT BEGIN:VEVENT SUMMARY:N. G. Veselkova DTSTART:20250319T124500Z DTEND:20250319T134500Z DTSTAMP:20260404T111243Z UID:QOARTseminar/11 DESCRIPTION:Title: Creation and manipulation of Schrödinger cat states based on semiclassical predictions\nby N. G. Veselkova as part of Seminar on Q uantum Optics and Related Topics\n\n\nAbstract\nWe consider the generation of Schrödinger cat states using a quantum measurement-induced logical ga te where entanglement between the input state of the target oscillator and the Fock state of the ancillary system produced by the quantum non-demoli tion entangling CZ operation is combined with the homodyne measurement. We utilize the semiclassical approach to construct both the input-output map ping of the field variables in the phase space and the wave function of th e output state. This approach is found to predict that the state at the ga te output is represented by a minimum disturbed cat-like state which is a superposition of two initial state copies symmetrically displaced by momen tum variable. For the target oscillator prepared in the coherent state\, w e show that the fidelity between the exact solution for the gate output st ate and the “perfect” Schrödinger cat reconstructed from the semiclas sical theory can reach high values exceeding 0.99.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/11/ END:VEVENT BEGIN:VEVENT SUMMARY:V.N. Sivkin DTSTART:20250328T120000Z DTEND:20250328T133000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/12 DESCRIPTION:Title: Tomography and Radon transform\nby V.N. Sivkin as part of Seminar on Quantum Optics and Related Topics\n\n\nAbstract\nMathematical tomography is a section of mathematics that describes methods for determin ing the structure of an object using scattering data. Such problems arise in microscopy\, medicine\, and technical control. In this report\, we will write out the basic differential equation of X-ray tomography. In the cou rse of its solution\, the Radon transform arises. We will establish a conn ection between the Fourier transform and the Radon transform\, and get acq uainted with the methods of its inversion.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/12/ END:VEVENT BEGIN:VEVENT SUMMARY:D.B. Zotev DTSTART:20250410T130000Z DTEND:20250410T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/13 DESCRIPTION:Title: On continuous observables in quantum mechanics\nby D.B. Z otev as part of Seminar on Quantum Optics and Related Topics\n\n\nAbstract \nThe theory of continuous observables in quantum mechanics has been arisi ng mistrust among mathematicians. Von Neumann banished from it the delta-f unction and such exotic entities as "Hermitian product matrices" with cont inuous indices and quasi-elements in the form of generalized functions. Th anks to von Neumann the paradigm has been spread according to which the st ate space of a quantum system must only be Hilbert. De'facto he replaced C openhagen quantum mechanics by a new theory with new physical consequence s. In addition\, along with the delta-function\, quantum mechanics in many ways lost its heuristic power. Dirac brilliantly anticipated the theory of generalized functions and\, in fact\, there was no need for such a refo rm. The report presents the theory of continuous observables in the formal form given to it by Heisenberg and Dirac. At the same time\, Dirac's appr oach is strictly formalized within the framework of the theory of generali zed functions. But Hilbert spaces are met here too.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/13/ END:VEVENT BEGIN:VEVENT SUMMARY:I.E. Protsenko DTSTART:20250415T120000Z DTEND:20250415T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/14 DESCRIPTION:Title: Theoretical modelling of superradiant lasers and other open q uantum resonant systems\nby I.E. Protsenko as part of Seminar on Quant um Optics and Related Topics\n\n\nAbstract\nAn approach for solving the st ationary nonlinear quantum Langevin equations for micro-lasers and other s mall resonant optical devices (for nonlinear optics\, plasmonics etc.) is presented. The method uses frequency dependent operators and calculates th e mean fluctuation power spectra and photon number. Various approximations for finding analytical expressions are shown. Results for thresholdless l asing\, collective Rabi splitting\, super-thermal photon statistics and th e power increase by the population fluctuations for the superradiant laser s are discussed.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/14/ END:VEVENT BEGIN:VEVENT SUMMARY:S. Lakshmi Bala DTSTART:20250425T130000Z DTEND:20250425T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/15 DESCRIPTION:Title: Optimal sensing of photon addition and subtraction on quantiz ed light\nby S. Lakshmi Bala as part of Seminar on Quantum Optics and Related Topics\n\n\nAbstract\nPhoton addition to\, and subtraction from qu antum states of light is of immense current interest\, both experimentally and theoretically. We identify a set of markers of photon addition to coh erent light and nonclassical single mode states of light such as the squee zed vacuum and the cat states\, which are directly computable from relevan t optical tomograms. These markers quantify the ‘distance’ between pro bability density functions corresponding to different states. Examples of such markers are the Wasserstein distance\, the Kullback Leibler divergenc e and the Bhattacharyya distance.\nAlthough the details in the manner in w hich these markers vary with changes in relevant parameters\, depends on t he state concerned\, they are\, in general\, sensitive to the underlying i nterference structures that arise in the tomogram after photon addition/su btraction. Our procedure is universally applicable to the cat and squeezed states\, the former displaying the characteristic negativity in its Wigne r function\, while the latter does not do so. We explicate this in the cas e of the squeezed vacuum and even coherent states and show that photon add ition (or subtraction) is mirrored in the shift in the intensity of specif ic regions in the tomogram.\nIn the case of coherent light\, the amplifica tion gain due to photon addition\, and the dependence of quadrature varian ces on relevant parameters\, are calculated from the tomograms (circumvent ing state reconstruction)\, and compared with results obtained (after stat e reconstruction)\, in a recent experiment reported in the literature. Our results match well with the fidelity and variance plots obtained by the e xperimenters.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Ray-Kuang Lee DTSTART:20250430T130000Z DTEND:20250430T140000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/16 DESCRIPTION:Title: Adding or subtracting a single photon is the same\, but only for pure squeezed vacuum states\nby Ray-Kuang Lee as part of Seminar o n Quantum Optics and Related Topics\n\n\nAbstract\nThe addition of a singl e photon to a light field can lead to exactly the same outcome as the subt raction of a single photon: starting from the same initial state\, both pr ocedures can generate the same final quantum state. We prove that this ide ntity-of-outcome is true for pure squeezed vacuum states of light\, and in some sense only for those. We show that mixed states can show this identi ty-of-outcome for the addition or subtraction of a photon if they are gene rated from the incoherent sums of pure squeezed vacuum states with the sam e squeezing. We point out that our results give a reinterpretation to the fact that pure squeezed.\n\nPublication:\n\nOle Steuernagel\, Shao-Hua Hu\ , and Ray-Kuang Lee\, APL Quantum 2\, 016117 (2025)\; https://doi.org/10.1 063/5.0246230\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/16/ END:VEVENT BEGIN:VEVENT SUMMARY:R. Sh. Kalmetev DTSTART:20250527T130000Z DTEND:20250527T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/17 DESCRIPTION:Title: On Averaging of One-Parameter Semigroups and Their Generators \nby R. Sh. Kalmetev as part of Seminar on Quantum Optics and Related Topics\n\n\nAbstract\nThe talk discusses methods for averaging one-paramet er semigroups and their generators\, focusing on random unbounded operator s in Hilbert spaces. Key findings include the construction of generalized expectations through Chernoff equivalence\, illustrative examples for reso lvent and semigroup averaging\, and the role of Feynman formulas in approx imating quantum evolution operators. The results highlight the flexibility and limitations of these methods\, offering insights into their use in di ssipative dynamics\, quantization ambiguities\, and stochastic differentia l equations in mathematical physics.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/17/ END:VEVENT BEGIN:VEVENT SUMMARY:N. S. Arefyeva DTSTART:20250617T130000Z DTEND:20250617T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/18 DESCRIPTION:Title: Non-Markovian entropy production and its connection to global entanglement in quantum chaos\nby N. S. Arefyeva as part of Seminar o n Quantum Optics and Related Topics\n\n\nAbstract\nWe focus on the problem of identifying dynamical signatures of quantum behavior\, particularly qu antum chaos. Recently\, we proposed a method for efficiently computing the dynamics of an open quantum system\, based on emergent integrals of motio n that dynamically form in the environment after a local quench. These int egrals carry away the system’s entanglement entropy.\n\nWe show that in the Markovian limit\, resembling ancilla-based models\, entropy production grows linearly and integrable and chaotic behavior are indistinguishable. In contrast\, in the non-Markovian regime\, entropy production closely fo llows the Meyer–Wallach global entanglement measure and serves as a sens itive probe of quantum chaos. Thus\, we propose non-Markovian entropy prod uction as a marker of quantum chaos.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/18/ END:VEVENT BEGIN:VEVENT SUMMARY:A. A. Aleksandrov DTSTART:20250707T130000Z DTEND:20250707T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/19 DESCRIPTION:Title: Quantum analog of classical Arnold tongues\nby A. A. Alek sandrov as part of Seminar on Quantum Optics and Related Topics\n\n\nAbstr act\nI will review papers by Lee et. al related to synchronization of open quantum systems. Each system is nothing more than a simple harmonic oscil lator\, interacting with an environment. To start with\, I present the ess ential facts about phase-locking and synchronization in simple dynamical s ystem on torus. Next one will see how does the quatum limit cylce can appe ar\, then we will see how does the classical synchronization domain (Arnol d tongue) evolves into its quantum version. The talk is on physical level of rigour.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/19/ END:VEVENT BEGIN:VEVENT SUMMARY:M. A. Gorlach DTSTART:20250717T120000Z DTEND:20250717T133000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/20 DESCRIPTION:Title: Time-optimal transfer of the quantum state in long qubit arra ys\nby M. A. Gorlach as part of Seminar on Quantum Optics and Related Topics\n\n\nAbstract\nRecent technological advances have allowed the fabri cation of large arrays of coherently operating coupled qubits\, serving as prototypes for quantum processors. However\, the optimal control of such systems is notoriously challenging because of the extremely large number o f degrees of freedom. The lack of such control limits the potential of lar ge-scale quantum systems.\nIn this talk\, I will discuss a model problem o f quantum state transfer in a large nearest-neighbor-coupled qubit array. I will present the optimal control strategy that simultaneously achieves m aximal fidelity and minimal transfer time\, reaching the quantum speed lim it in a lattice with time-varying couplings. \n\nRelated paper:\n\nhttps:/ /arxiv.org/abs/2501.11933\, accepted to Physical Review Letters\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/20/ END:VEVENT BEGIN:VEVENT SUMMARY:I. V. Iorsh DTSTART:20250725T130000Z DTEND:20250725T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/21 DESCRIPTION:Title: Polaron effect in waveguide quantum optomechanics\nby I. V. Iorsh as part of Seminar on Quantum Optics and Related Topics\n\n\nAbst ract\nIn my talk I will discuss the impact of the quantized mechanical mot ion of optically trapped atoms\, arranged in proximity to a one-dimensiona l waveguide\, on the propagation of polariton modes. Our study identifies a regime of resonant phonon-assisted mixing between lower and upper polari tons\, resulting in a pronounced polaron effect. This effect is characteri zed by the formation of new band gaps and the appearance of weakly dispers ive states within the original polariton band gap. The polaron spectrum\, which can be directly probed via resonant elastic scattering\, provides no vel opportunities for quantum optical applications. These findings open av enues for enhanced control in state-of-the-art waveguide quantum electrody namics experiments with cold atoms\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/21/ END:VEVENT BEGIN:VEVENT SUMMARY:M. V. Bastrakova DTSTART:20250728T130000Z DTEND:20250728T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/22 DESCRIPTION:Title: Josephson "flying qubit" revival: Flux-based control optimiza tion\nby M. V. Bastrakova as part of Seminar on Quantum Optics and Rel ated Topics\n\n\nAbstract\nA decade ago\, Josephson "flying qubits" based on adiabatic superconducting logic cells showed promise as quantum data bu ses\, but their development stalled due to the incompatibility of traditio nal qubit control methods with their design. We revisit this concept by ex ploring the control of the inductively shunted two-junction superconductin g interferometer (adiabatic quantum flux parametron\, AQFP) in the quantum regime using unipolar magnetic field pulses generated by adiabatic superc onducting electronics. Our research demonstrates the feasibility of high f idelity quantum operations (fidelity more than 99.99 percent) in this syst em via Landau–Zener tunneling. To this end\, a method is proposed for se lecting the duration and shape of control pulses to eliminate unwanted lea kage into high-lying states in AQFP-based systems.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/22/ END:VEVENT BEGIN:VEVENT SUMMARY:A. Yu. Karasev DTSTART:20250806T130000Z DTEND:20250806T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/23 DESCRIPTION:Title: Projection approach for composite open quantum systems\nb y A. Yu. Karasev as part of Seminar on Quantum Optics and Related Topics\n \n\nAbstract\nThis report presents the application of the Nakajima–Zwanz ig projection method to the derivation of kinetic equations for systems tr eated as weakly interacting open subsystems. As illustrative examples\, we analyze the Jaynes–Cummings model with dissipation and the spontaneous parametric down-conversion model involving two dissipative modes. For both systems\, the approach enables a systematic derivation of corrections to the parametric approximation by accounting for quantum depletion of the pu mping field.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/23/ END:VEVENT BEGIN:VEVENT SUMMARY:S. S. Sysoev DTSTART:20250827T130000Z DTEND:20250827T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/24 DESCRIPTION:Title: Some Practical Problems of Quantum Gate Teleportation (QGT)\nby S. S. Sysoev as part of Seminar on Quantum Optics and Related Topic s\n\n\nAbstract\nQuantum teleportation is unquestionably an important reso urce\, especially in the one-way computation model. However\, we will focu s on the circuit-based model and explore what this technique can contribut e to its toolset. Quantum algorithms can benefit from teleportation if we teleport gates rather than states. This idea was investigated two decades ago by Gottesman and Chuang\, whose paper optimistically claimed that tele portation is a universal computational resource. \nApart from teleporting the CX gate within the KLM protocol\, though\, it is hard to find convinc ing practical uses for this technique. Furthermore\, the derivation of the CX-gate procedure itself was never fully clarified. In this talk we will revisit their method\, extend it to the Toffoli gate\, offer fresh motivat ion for pursuing gate teleportation\, and identify the obstacles encounter ed along the way.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/24/ END:VEVENT BEGIN:VEVENT SUMMARY:A. S. Solntsev DTSTART:20251014T060000Z DTEND:20251014T083000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/25 DESCRIPTION:Title: Nonlinear quantum optics: from photonic chips to nanoscale\nby A. S. Solntsev as part of Seminar on Quantum Optics and Related Topi cs\n\n\nAbstract\nQuantum optics has a range of applications including sec ure communication\, precise sensing\, and ultrafast computing. Optical non linearities have long been utilised as a source of quantum light. Nowadays \, nonlinear quantum photonics is undergoing rapid miniaturisation\, movin g from bulk optics\, to photonic chips\, and\, more recently\, to nano-sca le components. This transition is what this talk is about.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/25/ END:VEVENT BEGIN:VEVENT SUMMARY:M. A. Gavreev DTSTART:20251016T130000Z DTEND:20251016T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/26 DESCRIPTION:Title: Tensor Networks: From Numerical Methods to Understanding Quan tum Systems\nby M. A. Gavreev as part of Seminar on Quantum Optics and Related Topics\n\n\nAbstract\nTensor networks are a modern mathematical l anguage that allows for a compact and efficient description of many-body q uantum states\, where direct computation becomes impossible. This talk dis cusses how this approach helps to understand the structure of entanglement and the dynamics of systems with a large number of particles\, as well as how it is used for the numerical solution of quantum mechanical problems. The main ideas underlying tensor networks\, intuitive examples of how the y work\, and key directions of practical application — from modeling man y-body quantum systems to describing states of light — will be presented . Special attention is given to how tensor methods unify theory\, computat ion\, and experiment\, opening new possibilities for the study of quantum systems.\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/26/ END:VEVENT BEGIN:VEVENT SUMMARY:I. D. Remizov DTSTART:20251023T130000Z DTEND:20251023T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/27 DESCRIPTION:Title: Estimates on the rate of convergence of Chernoff approximatio ns to C0 -semigroups (Part 1 of 2)\nby I. D. Remizov as part of Semina r on Quantum Optics and Related Topics\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/27/ END:VEVENT BEGIN:VEVENT SUMMARY:I. D. Remizov DTSTART:20251030T130000Z DTEND:20251030T143000Z DTSTAMP:20260404T111243Z UID:QOARTseminar/28 DESCRIPTION:Title: Estimates on the rate of convergence of Chernoff approximatio ns to C0 -semigroups (Part 2 of 2)\nby I. D. Remizov as part of Semina r on Quantum Optics and Related Topics\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/QOARTseminar/28/ END:VEVENT END:VCALENDAR