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BEGIN:VEVENT
SUMMARY:R. Singh
DTSTART:20240902T055000Z
DTEND:20240902T060000Z
DTSTAMP:20260422T212725Z
UID:QOART/1
DESCRIPTION:Title: Op
ening\nby R. Singh as part of Quantum Optics and Related Topics\n\nAbs
tract: TBA\n
LOCATION:https://researchseminars.org/talk/QOART/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. V. Masalov
DTSTART:20240902T060000Z
DTEND:20240902T070000Z
DTSTAMP:20260422T212725Z
UID:QOART/2
DESCRIPTION:Title: Un
solved problem in quantum optics\nby A. V. Masalov as part of Quantum
Optics and Related Topics\n\n\nAbstract\nThe report is devoted to the prob
lem of quantum calculations of radiation fields in nonlinear optical media
under conditions of powerful light beams\, i.e. when the number of photon
s is huge. The attempts known to the author to solve this problem are cons
idered.\n
LOCATION:https://researchseminars.org/talk/QOART/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. V. Akimov
DTSTART:20240902T074000Z
DTEND:20240902T091000Z
DTSTAMP:20260422T212725Z
UID:QOART/3
DESCRIPTION:Title: To
ward quantum simulations with Thulium atoms\nby A. V. Akimov as part o
f Quantum Optics and Related Topics\n\n\nAbstract\nBose-Einstein condensat
ion (BEC) is a powerful tool for a wide range of research activities\, a l
arge fraction of which is related to quantum simulations. Various problems
may benefit from different atomic species. Thulium atoms possess dipole m
oment of 4 Bohr magneton in the ground state\, allowing long-term interact
ions. It also has number of non-chaotic low-field Feshbach resonances\, al
lowing fine control of the near-filed interactions. It also has relatively
simple level structure compared to the other magnetic lanthanoids and thu
s is a quite promising subject for applications in quantum simulations.\nN
evertheless\, cooling down novel species interesting for quantum simulatio
ns to BEC temperatures requires a substantial amount of optimization and i
s usually considered to be a difficult experimental task. Here we report o
n implementation of the Bayesian machine learning technique to optimize th
e evaporative cooling of thulium atoms and achieved BEC in an optical dipo
le trap. Two dipole traps were used: 532 nm light and 1064 nm light\, in b
oth the condensation was achieved. We also analyzed the atomic loss mechan
ism for the 532 nm optical trap\, used in the Bose-condensation experiment
\, and compares it with the alternative and more traditional micron-range
optical dipole trap.\nWhile the condensate of the thulium atom has a lot o
f 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 was succ
essfully utilized to diagnose an optical lattice and detect unwanted refle
ctions in the experiments with the 1064 nm optical lattice\, which will fu
rther be used in a quantum gas microscope experiment.\nThis work was suppo
rted by Rosatom in the framework of the Roadmap for Quantum computing (Con
tract No. 868-1.3-15/15-2021 dated October 5\, 2021).\n
LOCATION:https://researchseminars.org/talk/QOART/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:D.A. Chermoshentsev
DTSTART:20240902T092000Z
DTEND:20240902T102000Z
DTSTAMP:20260422T212725Z
UID:QOART/4
DESCRIPTION:Title: No
nlinear Photonics for Coherent Computing and Signal Generation\nby D.A
. Chermoshentsev as part of Quantum Optics and Related Topics\n\n\nAbstrac
t\nOur scientific interests lie in the fields of nanophotonics\, quantum o
ptics\, and quantum computing. We are engaged in the development and study
of the nonlinear and quantum properties of the electromagnetic field in i
ntegrated photonic circuits. The use of such integrated systems allows for
the development of compact devices with unique properties: stable laser s
ources with low phase noise\, spectrometers\, gyroscopes\, sensors\, sourc
es of coherent and soliton frequency combs\, microwave signal generators\,
sources of non-classical states of light\, as well as optical and quantum
computers. The presentation will discuss the latest results obtained from
research in these systems.\n
LOCATION:https://researchseminars.org/talk/QOART/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:R. Singh
DTSTART:20240902T103000Z
DTEND:20240902T110000Z
DTSTAMP:20260422T212725Z
UID:QOART/5
DESCRIPTION:Title: Th
e formation of Schrodinger cat-like states in the process of spontaneous p
arametric down-conversion\nby R. Singh as part of Quantum Optics and R
elated Topics\n\n\nAbstract\nThe formation of Schrodinger cat-like states
during the spontaneous parametric down-conversion process (SPDC) is studie
d when the pump mode is considered quantum and depleted. The Schrodinger c
at-like state is formed in the fundamental and second harmonic modes\, and
the negativity in both modes is studied for certain initial state conditi
ons and interaction lengths. The Wigner function is used to visualize qual
itatively Schrodinger cat-like states.\n\nhttps://arxiv.org/abs/2405.14526
\n
LOCATION:https://researchseminars.org/talk/QOART/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:E. A. Anashkina
DTSTART:20240902T120000Z
DTEND:20240902T130000Z
DTSTAMP:20260422T212725Z
UID:QOART/6
DESCRIPTION:Title: Ph
ase-sensitive symmetry breaking in microresonators with Kerr nonlinearity<
/a>\nby E. A. Anashkina as part of Quantum Optics and Related Topics\n\n\n
Abstract\nSpontaneous symmetry breaking (SSB) is a fundamentally important
concept known in many areas of physics: particle physics\, condensed matt
er physics\, and optics\, to name a few. In photonics\, there has been an
increasing interest in studying symmetry breaking\, chiral and nonreciproc
al light propagation in optical macro- and microresonators with cubic nonl
inearities. Here\, we demonstrate theoretically and experimentally that li
near coupling due to the backscattering between two counterpropagating mod
es in a microresonator with Kerr nonlinearity leads to extreme sensitivity
of the intensity asymmetry of light states to the relative phase between
the bidirectional pumps of equal power. In the absence of linear coupling\
, the relative pump phase does not affect counterpropagating intraresonato
r intensities\, and two asymmetric states arise due to spontaneous symmetr
y breaking. Contrariwise\, in the presence of weak linear intermode coupli
ng\, the asymmetry of the states is deterministically controlled via chang
es in phase (for all phases except 0 and π). Spontaneous symmetry breakin
g at zero phase is suppressed when the linear intermode coupling is increa
sed\, while for the π phase it can be enhanced\, so that the overall thre
shold for the spontaneous symmetry breaking can be significantly lower for
nonzero linear coupling. These results are important for fundamental unde
rstanding of the processes in Kerr resonators and other systems with Kerr-
like nonlinearities and linear intermode coupling and have high prospects
for the development of photonic devices such as ultrasensitive sensors. Mo
reover\, the study of such systems also allows one to obtain fundamental r
esults that can be used outside of optics due to quantum-optical analogies
(for example\, for studying the well-known Bose-Hubbard dimer).\n\nThe wo
rk was supported by the Russian Science Foundation\, grant No.20-72-10188-
P.\n\nE.A. Anashkina\, A.V. Andrianov\, “Phase-sensitive symmetry breaki
ng in bidirectionally pumped Kerr microresonators\,” arXiv preprint arXi
v:2407.07594 (2024).\n
LOCATION:https://researchseminars.org/talk/QOART/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. K. Fedorov
DTSTART:20240902T134000Z
DTEND:20240902T144000Z
DTSTAMP:20260422T212725Z
UID:QOART/7
DESCRIPTION:Title: Qu
antum complexity and quantum information technologies\nby A. K. Fedoro
v as part of Quantum Optics and Related Topics\n\n\nAbstract\nComplexity i
s the cornerstone concept of physics\, and it plays a special role in the
context of quantum many-body physics. Recent progress in developing comput
ational devices based on quantum effects and demonstrations of solving var
ious tasks using them has actualized the question of the origin of the qua
ntum advantage. Although various attempts to quantify and characterize the
nature of quantum computational advantage have been made\, this question
in the general context remains open: There is no universal approach that h
elps to define a scope of problems that quantum computers are able to spee
d up\, theoretically and in practice. In this talk\, we review an approach
to this question based on the concept of complexity and reachability of q
uantum states. On the one hand\, the class of quantum states that is of in
terest for quantum computing should be complex\, i.e. non-simulatable with
classical computers with less than exponential resources. On the other ha
nd\, such quantum states should be reachable on a practical quantum comput
er. This means that a unitary corresponding to the transformation of quant
um states from initial to desired can be decomposed in a sequence of singl
e- and two-qubit gates with of no more than polynomial in the number of qu
bits. Our consideration paves the way towards understanding the scope of p
roblems that can be solved by a quantum computer by formulating a sequence
of statements and conjectures on various sets of quantum states.\n
LOCATION:https://researchseminars.org/talk/QOART/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. A. Sukhorukov
DTSTART:20240903T060000Z
DTEND:20240903T070000Z
DTSTAMP:20260422T212725Z
UID:QOART/8
DESCRIPTION:Title: Ph
oton-pair generation and quantum measurements with metasurfaces\nby A.
A. Sukhorukov as part of Quantum Optics and Related Topics\n\n\nAbstract\
nWe present the theoretical and experimental advances of our group on quan
tum photon-pair generation through spontaneous parametric down-conversion
in nonlinear metasurfaces\, underpinning quantum entanglement engineering
at a sub-wavelength scale for photon shaping with tailored polarization an
d spatial correlations. In particular\, we demonstrate experimentally the
generation of spatially entangled photon pairs through spontaneous paramet
ric down-conversion from a metasurface incorporating a nonlinear thin film
of lithium niobate covered by a silica meta-grating and achieve precise c
ontrol of the emission angle of photons. We also outline the applications
of metasurfaces quantum imaging combining ghost and all-optical scanning a
t infrared wavelengths and perform single-shot characterization of the ind
istinguishability between two photons.\n
LOCATION:https://researchseminars.org/talk/QOART/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.B. Mikhalychev
DTSTART:20240903T074000Z
DTEND:20240903T091000Z
DTSTAMP:20260422T212725Z
UID:QOART/9
DESCRIPTION:Title: Qu
antum measurement as a tool for probabilistic transformation of quantum li
ght states\nby A.B. Mikhalychev as part of Quantum Optics and Related
Topics\n\n\nAbstract\nSpecific properties of quantum measurements (backact
ion on the measured object\, randomness of the outcomes) lead to “hidden
” character of quantum information and hinder investigation of quantum s
ystems. On the other hand\, inevitable influence of the measuring device o
n the quantum system can serve as an instrument for steering it to a usefu
l target state. The talk is devoted to that aspect of quantum measurements
: special measurement types capable of creating various target states\; ge
neral ideas of measurement-induced control of quantum states\; interpretat
ion of dissipative (non-unitary) dynamics of quantum systems in terms of c
ontinuous measurements and its usage for generation of non-classical quant
um-optical states. Namely\, a class of “elimination” measurements is d
efined\, discussed\, and shown to be efficient for quantum light state man
ipulation. Further\, the idea is extended to the field of quantum imaging
and an approach to conditional enhancement of photonic state sensitivity t
o the illuminated object sub-Rayleigh features is proposed. The close conn
ection between dissipative non-unitary dynamics and measurement-induced st
eering of a quantum state makes the concept of “elimination” measureme
nts also fruitful for description of an optical system subjected to nonlin
ear coherent loss and showing its capability of generating sub-Poissonian
quantum-optical states.\n
LOCATION:https://researchseminars.org/talk/QOART/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:I.E. Sinayskiy
DTSTART:20240903T092000Z
DTEND:20240903T110000Z
DTSTAMP:20260422T212725Z
UID:QOART/10
DESCRIPTION:Title: Q
uantum Simulation of Open Quantum Systems\nby I.E. Sinayskiy as part o
f Quantum Optics and Related Topics\n\n\nAbstract\nA simulation of quantum
systems is one of the most exciting use cases for quantum computers. The
simulation of closed quantum systems\, or Hamiltonian simulation\, has bee
n explored in recent years. Novel methods have been developed\, improving
the widely used and wellknown Suzuki Lie Trotter product formulas. However
\, in many practical situations\, one must consider unavoidable interactio
n with the thermal environment. The success of quantum computers in simula
ting physical systems has led to the development of quantum algorithms to
simulate open quantum systems in the faulttolerant setting. However\, thes
e 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 qua
ntum simulation of quantum systems and focus on our recent work of reducin
g the gate complexity in the simulation of an open quantum system by using
two methods that rely on randomisation.\n
LOCATION:https://researchseminars.org/talk/QOART/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:S. Chaturvedi
DTSTART:20240903T120000Z
DTEND:20240903T133000Z
DTSTAMP:20260422T212725Z
UID:QOART/11
DESCRIPTION:Title: B
ose’s derivation of the Planck's distribution\, his notion of indistingu
ishability and its quantum counterpart: A comparison\nby S. Chaturvedi
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 distribu
tion we proceed to discuss its quantum counterpart. We highlight the commo
nalities and differences between all possible statistics that arise after
implementing respective notions of indistinguishabilty in the two scenario
s and bring out the role the theory of symmetric functions plays in achiev
ing this objective.\n
LOCATION:https://researchseminars.org/talk/QOART/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.B. Klimov
DTSTART:20240903T134000Z
DTEND:20240903T151000Z
DTSTAMP:20260422T212725Z
UID:QOART/12
DESCRIPTION:Title: D
iscrete phase-space description of N-partite quantum systems: from visuali
zation to quantification of quantum correlations\nby A.B. Klimov as pa
rt of Quantum Optics and Related Topics\n\n\nAbstract\nWe review the appli
cation of the discrete phase-space approach to analyzing quantum correlati
ons in many body systems. Starting with a microscopic description\, we pro
ceed to analyze global features of quantum states detectable in collective
measurements\, mainly focusing on N-qubit systems in the macroscopic limi
t N>>1. Applications to quantification/identification of quantum correlati
ons\, quantum tomography\, phase transitions\, quantum thermalization\, an
d stability under local noise are outlined. A generalization to higher loc
al dimensions is discussed.\n
LOCATION:https://researchseminars.org/talk/QOART/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:P. K. Panigrahi
DTSTART:20240904T060000Z
DTEND:20240904T070000Z
DTSTAMP:20260422T212725Z
UID:QOART/13
DESCRIPTION:Title: M
eso and Macroscopic Quantum States of Light\nby P. K. Panigrahi as par
t of Quantum Optics and Related Topics\n\n\nAbstract\nWe investigate the n
ature of correlated photons from three dipole-coupled two-level atomic sys
tems and find the clear signatures of the entangled matter states on the n
ature of the emitted photons. The presence of two phases\, as predicted by
Dicke a long time back\, is evident in the far-field spectrum. The phase
transition between these two phases and the behaviour of concurrence\, dis
cord and monogamy in both these phases are explicated. The effect of the a
tomic configuration is pointed out in the optical domain. We then investig
ate another macroscopic state of condensed photons\, where photonic superf
luidity and supersolidity are pointed out with exact solutions of the rele
vant mean field equations: nonlinear Schrodinger equation with a source. T
he earlier experimental observation of the superfluid phase opens the way
for the possible realization of photonic supersolidity. We further highlig
ht the deep connection between entanglement\, coherence\, and path predict
ability in the much-studied multi- slit experiments.\n\nRef:\n\n(1) M. K.
Parit et al.\, “Correlated photons of desired characteristics from a dip
ole coupled three-atom system”\, OSA Continuum 2 (8)\, pp. 2293-2307 (20
19).\n\n(2) Dynamical phase transition of photon condensate in an optical
cavity Neeraj\, MK Parit\, VM Vyas\, PK Panigrahi\,Journal of the Optical
Society of America B 38 (2)\, 476-481\n\n(3) A scheme to observe universal
breathing mode and Berezinskii–Kosterlitz–Thouless phase transition i
n a two-dimensional photon gas\, VM Vyas\, PK Panigrahi\, J Banerji\, Phys
ics Letters A 378 (20)\, 1434-1437\n\n(4) Coherence\, path predictability\
, and concurrence: A triality AK Roy\, N Pathania\, NK Chandra\, PK Panigr
ahi\, T Qureshi\, Physical Review A 10\,(3)\, 032209\n
LOCATION:https://researchseminars.org/talk/QOART/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:O. V. Tikhonova
DTSTART:20240904T074000Z
DTEND:20240904T084000Z
DTSTAMP:20260422T212725Z
UID:QOART/14
DESCRIPTION:Title: E
ntanglement and correlations of photons in bright squeezed vacuum light\nby O. V. Tikhonova as part of Quantum Optics and Related Topics\n\n\nAb
stract\nSpatial and spectral features as well as strong photon correlation
s of non-classical multi-photon squeezed electromagnetic fields are discus
sed. We consider the theoretical approach based on the Schmidt mode analys
is and able to describe analytically peculiarities of such bright squeezed
light with high agreement with experimental data. Methods to control and
manage the mode content\, degree of squeezing and photon entanglement are
analyzed. Their advantages and applied prospects are highlighted. Practica
l applications based on the non-classical features of squeezed fields for
precise quantum measurements and strong coupling to atomic systems are dis
cussed.\n
LOCATION:https://researchseminars.org/talk/QOART/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. E. Teretenkov
DTSTART:20240904T092000Z
DTEND:20240904T101000Z
DTSTAMP:20260422T212725Z
UID:QOART/15
DESCRIPTION:Title: M
ultimode quantum master equations: linear dynamics beyond quadratic genera
tors\nby A. E. Teretenkov as part of Quantum Optics and Related Topics
\n\n\nAbstract\nWe present several examples of quantum master equations su
ch that the dynamics of moments up to any finite order of bosonic creation
and annihilation operators is (exactly) closed and linear.\nNamely\, we c
onsider the quantum master equations which occur in the case of averaging
of unitary dynamics with quadratic generators with respect to classical Le
vy fields\, in particular with respect to Poisson and Wiener stochastic pr
ocesses. We show that the dynamics of the moments of any fixed order is de
scribed by the closed system of ordinary linear differential equations.\nW
e discuss some recent physical applications of these results.\n\nThe talk
is based on the works:\n\nT. Linowski\, A. Teretenkov\, L. Rudnicki\, Phys
ical Review A\, 106 (2022)\, 052206.\n\nD. D. Ivanov\, A. E. Teretenkov\,
Math. Notes\, 112:2 (2022)\, 318-322.\n\nA. E. Teretenkov\, Math. Notes\,
107:4 (2020)\, 695-698.\n
LOCATION:https://researchseminars.org/talk/QOART/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:W. V. Pogosov
DTSTART:20240904T120000Z
DTEND:20240904T123000Z
DTSTAMP:20260422T212725Z
UID:QOART/16
DESCRIPTION:Title: E
ffects of photon statistics in wave mixing on a single qubit\nby W. V.
Pogosov as part of Quantum Optics and Related Topics\n\n\nAbstract\nWe th
eoretically consider wave mixing under the irradiation of a single qubit b
y two photon fields. The first signal is a classical monochromatic drive\,
while the second one is a nonclassical light. Particularly\, we address t
wo examples of a nonclassical light: (i) a broadband squeezed light and (i
i) a periodically excited quantum superposition of Fock states with 0 and
1 photons. The mixing of classical and nonclassical photon fields gives ri
se to side peaks due to the elastic multiphoton scattering. We show that s
ide peaks structure is distinct from the situation when two classical fiel
ds are mixed. The most striking feature is that some peaks are absent. Thu
s\, the analysis of peak amplitudes can be used to probe photon statistics
in the nonclassical mode. A cascade of two-level superconducting artifici
al atoms – a source and a probe – strongly coupled to a semi-infinite
waveguide is a promising tool for observing such non-trivial phenomena. Th
e probe atom can scatter an antibunched output from the source\, thereby g
enerating the field with specific properties. We experimentally demonstrat
e wave mixing between non-classical light from the coherently pumped sourc
e and another coherent wave acting on the probe. We observe unique feature
s in the wave-mixing stationary spectrum that cannot be reproduced by mixi
ng two classical waves on the probe. These features are well described by
the theory for a strongly coupled cascaded system of two atoms.\n
LOCATION:https://researchseminars.org/talk/QOART/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. E. Afanas'ev
DTSTART:20240904T134000Z
DTEND:20240904T144000Z
DTSTAMP:20260422T212725Z
UID:QOART/17
DESCRIPTION:Title: Q
uantum metrology with atom chip\nby A. E. Afanas'ev as part of Quantum
Optics and Related Topics\n\n\nAbstract\nThe goal of quantum metrology is
to increase the sensitivity of physical fields measuring. It can be achie
ved by using quantum mechanics effects such as interferometry of quantum s
tates\, squeezing\, etc. Quantum sensors used as instruments for high sens
itivity measurements reached outstanding results in laboratory conditions.
There is currently a growing trend towards outdoor experimentation. The m
ain development trend is the decreasing of dimensions and power consumptio
n of quantum sensor in comparison with used sensors in classical approache
s. Increasing sensitivity of outdoor sensors will allows us to move to the
next technological level.\nAmong various types of quantum sensors\, the s
ensors using neutral atoms are promising. To increase the quantum senser s
ensitivity the approach of atomic state interference is used.\nAtom interf
erometry is considered as a platform for high precision fundamental experi
ments and for solving numerous applied problems [1]. For instance\, microw
ave atomic clock used interference pattern of Ramsey fringe for high stabi
lity of frequency standards. The precision of quantum sensors is limited b
y the quantum projection noise. Therefore\, the number of atoms forming th
e interference pattern is the cornerstone of quantum sensor. To reach high
precision of quantum sensors based on atom interferometry the effective s
ource of cold atoms is necessary. There are three types of atoms sources c
an be used for atom interferometry: (1) atomic beam\; (2) cold atoms in ma
gneto-optical trap (MOT)\; (3) ultracold atoms trapped on atom chip. The u
se of the first type of atom source leads to quantum sensors of large spat
ial dimensions. Cold atoms from MOT are actively used in quantum sensors\,
for instance\, in atomic gravimeter [2\,3]. The drawback of MOT as an ato
mic source is the temperature of atomic ensemble. In case of sub-Doppler c
ooling the temperature is about several microkelvins. Lower temperatures r
equire evaporative cooling. Unfortunately\, MOT is not suitable for evapor
ative cooling\, which is usually done in a magnetic trap.\nThe atom chip o
peration is based on a cold atom trapping near the microwire. In this case
a high gradient of magnetic field can be achieved relatively easy. Approa
ch for ultracold atom source sensor baser on atom chip has been demonstrat
ed with high bandwidth [4]. Until now\, most demonstrated atom chips have
been technically sophisticated\, with multiple layers of microwires to coo
l and trap atoms. We demonstrated single-layer atom chip which can be used
as atom source for atom interferometry and quantum sensors [5]. The new t
ype of single-layer atom chip developed\, which makes it possible to incre
ase the number of atoms up to 5?107 [6]. The magnetic trapping of atoms gi
ves the possibility to use evaporative cooling to reach the temperatures b
elow 1 mkK. It gives us the possibility of coherent manipulations with ato
mic ensemble.\n\nThe study was supported by the Russian Science Foundation
\, grant No. 23-22-00255.\n\nReferences\n\n[1] R. Geiger\, et al.\, AVS Qu
antum Sci. 2\, 024702 (2020).\n\n[2] V. Menoret\, et al.\, Sci Rep 8\, 123
00 (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 (2024).\n
LOCATION:https://researchseminars.org/talk/QOART/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:L.L. Sanchez-Soto
DTSTART:20240905T060000Z
DTEND:20240905T073000Z
DTSTAMP:20260422T212725Z
UID:QOART/18
DESCRIPTION:Title: Q
uantum Superresolution in Time and Frequency\nby L.L. Sanchez-Soto as
part of Quantum Optics and Related Topics\n\n\nAbstract\nAccurate time is
at the core of many modern technologies. I will present new schemes that a
llow one to achieve the ultimate quantum precision for the estimation of t
he time (or frequency) offset of an incoherent mixture of ultrashort pulse
s at the single-photon level. Amazingly\, these techniques are able to res
olve temporal separations 10 times smaller than the pulse duration\, as we
ll as imbalanced intensities differing by a factor of $10^2$. This represe
nts an improvement of more than an order of magnitude over the best standa
rd methods based on intensity detection and pave the way for new technolog
ies in this field.\n
LOCATION:https://researchseminars.org/talk/QOART/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. N. Rubtsov
DTSTART:20240905T074000Z
DTEND:20240905T084000Z
DTSTAMP:20260422T212725Z
UID:QOART/19
DESCRIPTION:Title: S
amplers: their description and its complexity\nby A. N. Rubtsov as par
t of Quantum Optics and Related Topics\n\n\nAbstract\nBosonic samplers are
quantum optical devices operating with multimode interference of non-clas
sical fields\, and are intended to provide practical demonstration of quan
tum advantage.\n
LOCATION:https://researchseminars.org/talk/QOART/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. P. Alodjants
DTSTART:20240905T092000Z
DTEND:20240905T102000Z
DTSTAMP:20260422T212725Z
UID:QOART/20
DESCRIPTION:Title: P
hysical graph structures for Quantum and Quantum-like Simulators\nby A
. P. Alodjants as part of Quantum Optics and Related Topics\n\n\nAbstract\
nCurrently speedup of information transmission represents one of the vital
interdisciplinary problems in computer science\, physics and engineering.
Recently\, various systems based on photonic information processing have
been suggested to get advantages in information processing. Typically\, su
ch a system mimics some quantum-like physical process that enables to solv
e NP-hard problem established by means of specific graph\, or the network.
In my talk\, I will analyze the quantum -inspired algorithms based on spe
cial network and/or quantum devices (simulators)\, leading to an accelerat
ion of the solution of some Karp problem. I discuss recently proposed by u
s novel quantum material (computational “hardware”) concept\, which en
ables interaction of two-level systems with the photonic field in two-dime
nsional materials possessing complex network interface . The multichannel
(multimode) structure of matter–field interaction leads to speedup of ph
otonic information processing. The results obtained pave the way for the d
esign of new photonic circuits\, quantum networks for efficient processing
of optical information.\n
LOCATION:https://researchseminars.org/talk/QOART/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. V. Khmelev
DTSTART:20240905T120000Z
DTEND:20240905T130000Z
DTSTAMP:20260422T212725Z
UID:QOART/21
DESCRIPTION:Title: S
atellite quantum communication: experiments in Russia and prospects\nb
y A. V. Khmelev as part of Quantum Optics and Related Topics\n\n\nAbstract
\nAbstract: The report will be devoted to satellite quantum key distributi
on (QKD)\, a direction in quantum communication that allows using a satell
ite to organize a secure communication channel on a global scale in order
to share cryptographic keys between users. Based on the recent research of
our group [1]\, the results of establishing a quantum-secured link betwee
n the Zvenigorod and Nanshan ground stations using the Micius satellite wi
ll be presented. Moreover\, we validate the simulation outcomes of our QKD
model for the developed realistic ground station using obtained experimen
tal findings\, which\, as we believe\, provide valuable insights on the ap
plied 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. Entropy 25(4)
\, 670 (2023)\n
LOCATION:https://researchseminars.org/talk/QOART/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:B. I. Bantysh
DTSTART:20240905T134000Z
DTEND:20240905T151000Z
DTSTAMP:20260422T212725Z
UID:QOART/22
DESCRIPTION:Title: R
esolution limits for multiple single-photon emitters\nby B. I. Bantysh
as part of Quantum Optics and Related Topics\n\n\nAbstract\nFluorescent m
icroscopy is essential for many biological applications. It uses dye molec
ules or quantum dots that emit photons to create images. The resolution of
such emitters is limited by the Rayleigh criterion. In recent years\, sev
eral attempts have been made to overcome this limit for resolving two sing
le-photon emitters. However\, for emitters with unbalanced intensities\, t
he absolute error in determining the distance increased as the sources mov
ed closer together [1]. In a recent study\, we demonstrated that a more ac
curate 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\, Realisti
c sub-rayleigh imaging with phase-sensitive measurements\, New Journal 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 Rayleigh's c
urse for two unbalanced single-photon emitters using BLESS technique. arXi
v preprint arXiv:2112.13244 (2024).\n
LOCATION:https://researchseminars.org/talk/QOART/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:E. Losero
DTSTART:20240906T063000Z
DTEND:20240906T073000Z
DTSTAMP:20260422T212725Z
UID:QOART/23
DESCRIPTION:Title: N
itrogen Vacancy (NV) centers in diamond for bio-sensing\nby E. Losero
as part of Quantum Optics and Related Topics\n\n\nAbstract\nNitrogen-vacan
cy (NV) centers are color-defects in the diamond crystal lattice which hav
e raised a lot of attention in the last decades for their promising sensin
g capabilities (especially for magnetic field and temperature)\, based on
spin-dependent photoluminescence. Moreover\, diamond biocompatibility and
good sensitivity at room temperature naturally lead to biological applicat
ions. Both bulk diamond and nanodiamonds can be used in this context\, eac
h presenting its own advantages and challenges.\n\nIn this presentation\,
I’ll describe our recent results in both directions. On one side I'll di
scuss how diamond chips can be nanostructured and used as substrates for c
ellular growth. On the other\, I'll show how nanodiamonds can be used for
nanoscale thermometry inside cells. Both approaches can be combined with e
xisting measurements techniques and give new insights on many biological p
rocesses which are still not completely understood.\n
LOCATION:https://researchseminars.org/talk/QOART/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. B. Fedotov
DTSTART:20240906T074000Z
DTEND:20240906T084000Z
DTSTAMP:20260422T212725Z
UID:QOART/24
DESCRIPTION:Title: F
our-wave mixing in photonic crystal fibers for generation of tailored quan
tum states of light\nby A. B. Fedotov as part of Quantum Optics and Re
lated Topics\n\n\nAbstract\nWe demonstrate a versatile fiber-optic platfor
m for the generation of tailored quantum states of light\, designed to enh
ance the performance of quantum sensing and imaging. The developed platfor
m is based on optical fibers of special design\, including photonic-crysta
l fibers (PCFs).\n\nThe design of optical fibers is optimized to provide a
n ultrahigh-contrast generation of entangled photon pairs confined to enta
nglement volumes many orders of magnitude smaller than the entanglement vo
lumes attainable through spontaneous parametric down-conversion. Four-wave
mixing (FWM) with cross-polarized pump and cross-polarized sidebands enab
les efficient generation of entangled photon pairs. Generation of cross-po
larized photon pairs is achieved by coupling the laser pump into orthogona
l polarization modes of a highly birefringent\, highly nonlinear\, anomalo
usly dispersive PCF. The contrast of photon pairs against the Raman noise
is enhanced by setting the pump wavelength to lie deeply within the anomal
ous dispersion region of the fiber. Broadband quantum states of light gene
rated via vectorial FWM are tailored\, by varying the pump wavelength and
polarization geometry\, from a high-purity\, low-dimensional entangled sta
te to a high-entropy entangled state in a space of a very high dimensional
ity.\n
LOCATION:https://researchseminars.org/talk/QOART/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yu. A. Nosal
DTSTART:20240906T093000Z
DTEND:20240906T100000Z
DTSTAMP:20260422T212725Z
UID:QOART/25
DESCRIPTION:Title: D
ynamics of moments of higher orders in exactly solvable models of the theo
ry 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 Leibniz-typ
e formula has been derived which allows one to compute the action of the c
onjugate Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) generator on the pro
duct of the creation and annihilation operators\, up to higher orders. Als
o\, the Heisenberg equations for arbitrary moments of higher orders of the
birth and annihilation operators in the case of a generator in the form o
f GKSL quadratic in terms of the bosonic creation and annihilation operato
rs have been obtained in explicit form. Moreover\, solutions of such equat
ions in the case of time-dependent coefficients have been obtained. In add
ition\, 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 obtained in th
e paper\, analogous equations were derived for the quantum master equation
arising after averaging the dynamics by a quadratic generator over a clas
sical Poisson process. This allowed us to show that the dynamics of arbitr
ary moments of finite order of the creation and annihilation operators in
this case is completely determined by a finite number of linear differenti
al equations.\n
LOCATION:https://researchseminars.org/talk/QOART/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:M.V. Fedorov
DTSTART:20240906T130000Z
DTEND:20240906T133000Z
DTSTAMP:20260422T212725Z
UID:QOART/26
DESCRIPTION:Title: V
ariations of the degree of angular entanglement in noncollinear regimes of
Spontaneous Parametric Down-Conversion (SPDC)\nby M.V. Fedorov as par
t of Quantum Optics and Related Topics\n\n\nAbstract\nAs known\, the proce
ss of Spontaneous Parametric Down-Conversion in birefringent crystals (SPD
C) produces states of photon pairs [1-3] which can be entangled. The varia
bles of the biphoton wave function can be different and characterizing dif
ferent degrees of freedom of photons: their polarizations\, or propagation
angles\, or frequencies of photons ω1 and ω2. In the last case one can
speak about spectral entanglement of sates characterized by the wave funct
ion Ψ(ω1\, ω2). The phenomenon of spectral entanglement and its degree
were rather thoroughly investigated in the work [4]\, both theoretically a
nd experimentally . On the other hand\, the double Fourier transformation
of Ψ(ω1\, ω2) gives the temporal biphoton wave function Φ(t1\, t2)\, i
n which the time variables t1 and t2 can be interpreted as the arrival tim
es 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. Cari
cato\, M.V. Fedorov\, M. Genovese\, S.P. Kulik\, EPL\, 87\, 64003 (2009).\
n
LOCATION:https://researchseminars.org/talk/QOART/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.A. Kalachev
DTSTART:20240906T134000Z
DTEND:20240906T141000Z
DTSTAMP:20260422T212725Z
UID:QOART/27
DESCRIPTION:Title: Q
uantum hashing via single-photon states\nby A.A. Kalachev as part of Q
uantum Optics and Related Topics\n\n\nAbstract\nA quantum hashing is a pro
mising generalization of the cryptographic hashing concept on the quantum
domain. In this case\, the hash function encodes a classical input state i
nto a quantum state so that to optimize the trade-off between one-way prop
erty and collision resistance. In the present work\, we develop a quantum
hashing technique wherein a quantum hash is constructed as a sequence of s
ingle-photon qubits [1] or qudits [2]. A proof-of-principle implementation
of the quantum hashing protocol using orbital-angular momentum encoding o
f single photons demonstrates good agreement with theoretical predictions.
In particular\, it shows that the number of qudits decreases with increas
e of their dimension for an optimal ratio between collision probability an
d decoding probability of the hash [2]. The prospects of increasing dimens
ion of information carriers\, which makes quantum hashing with single phot
ons more efficient\, are discussed [3].\n\n[1] D. A. Turaykhanov\, D. O. A
kat'ev\, A. V. Vasiliev\, F. M. Ablayev\, and A. A. Kalachev. Quantum hash
ing via single-photon states with orbital angular momentum. Physical Revie
w A\, 104\, 052606 (2021)\n\n[2] D.O. Akat’ev\, A.V. Vasiliev\, N.M. Sha
feev\, F.M. Ablayev\, A.A. Kalachev. Multiqudit quantum hashing and its im
plementation based on orbital angular momentum encoding. Laser Physics Let
ters 19\, 125205 (2022)\n\n[3] D. A. Turaykhanov\, N.M. Shafeev\, A. V. Va
siliev\, F. M. Ablayev\, and A. A. Kalachev. Quantum hashing with orbital
angular momentum and polarization encoding. (to be submitted)\n
LOCATION:https://researchseminars.org/talk/QOART/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rajiuddin Sk
DTSTART:20240907T060000Z
DTEND:20240907T063000Z
DTSTAMP:20260422T212725Z
UID:QOART/28
DESCRIPTION:Title: R
ole of Stark shift effect in preserving quantum correlations\nby Rajiu
ddin Sk as part of Quantum Optics and Related Topics\n\n\nAbstract\nIn thi
s talk\, I will present an analysis of the dynamics of quantum correlation
s in a\nsystem of two two-level atoms undergoing two-photon transitions vi
a an intermediate virtual\nstate. Each atom is coupled to a dissipative re
servoir at zero temperature\, with the presence\nof the Stark shift effect
playing a crucial role. We explore the exact expressions for Bures\ndista
nce entanglement\, trace distance discord\, and local quantum uncertainty
under two\ndifferent environmental initial conditions: the ground state an
d the first excited state. Notably\,\nthe first excited state reveals the
influence of both Stark shift parameters\, whereas the\nground state only
highlights one. Our findings indicate that quantum correlations can be\nma
intained for extended periods due to the Stark shift effect\, with a more
pronounced impact\nobserved in non-Markovian reservoirs\, even at minimal
Stark shift values. Additionally\, we\nidentify a sudden change phenomenon
in local quantum uncertainty\, marked by an abrupt\nshift in the decay ra
te. These results are crucial for understanding how to preserve quantum\nc
orrelations\, which are essential for optimizing performance in quantum in
formation\nprocessing.\n\nReference:\n\n(1) Chandra\, Nitish Kumar\, Rajiu
ddin Sk\, and Prasanta K. Panigrahi. "Preservation and\nenhancement of qua
ntum correlations under Stark effect." Journal of Modern Optics 70.4 (2023
):\n232-242.\n\n(2) Bashkirov\, E. K.\, and M. S. Rusakova. "Entanglement
for two-atom Tavis–Cummings model with\ndegenerate two-photon transition
s in the presence of the Stark shift." Optik 123.19 (2012): 1694-1699.\n
LOCATION:https://researchseminars.org/talk/QOART/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. Yu. Karasev
DTSTART:20240907T064000Z
DTEND:20240907T071000Z
DTSTAMP:20260422T212725Z
UID:QOART/29
DESCRIPTION:Title: H
igh order quantum corrections to the parametric approximation\nby A. Y
u. Karasev as part of Quantum Optics and Related Topics\n\n\nAbstract\nThi
s report presents the kinetic equations for an open two-level system weakl
y interacting with a dissipative laser field. Corrections to the parametri
c approximation in all orders of perturbation theory are calculated. We st
udied the contribution of the coherent state of the environment to the ren
ormalization of the initial conditions.\n
LOCATION:https://researchseminars.org/talk/QOART/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:J. Lugani
DTSTART:20240907T074000Z
DTEND:20240907T084000Z
DTSTAMP:20260422T212725Z
UID:QOART/30
DESCRIPTION:Title: I
ntegrated platforms for quantum information processing\nby J. Lugani a
s part of Quantum Optics and Related Topics\n\n\nAbstract\nIntegrated opti
cal platforms are bound to play crucial role in developing quantum optical
technologies. Benefitting from their inherent stability\, scalability and
tunability\, different integrated platforms are being widely explored for
the generation and manipulation of photonics qubits. In this work\, I wil
l provide a brief overview of how such quantum tasks are realized on optic
al chips. In addition\, I will focus on a novel platform based on thin fil
m lithium niobate to develop such quantum optical devices\n
LOCATION:https://researchseminars.org/talk/QOART/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.V. Andrianov
DTSTART:20240907T092000Z
DTEND:20240907T110000Z
DTSTAMP:20260422T212725Z
UID:QOART/31
DESCRIPTION:Title: K
err squeezing in optical waveguides and its use to improve the sensitivity
of interferometers\nby A.V. Andrianov as part of Quantum Optics and R
elated Topics\n\n\nAbstract\nSqueezed light is one of the key resources of
photonic quantum technology. Among the various applications of squeezed l
ight states\, measurement beyond the standard quantum limit is one of the
most prominent. Squeezed light is regularly used in large-scale gravitatio
nal wave detectors. Among the various nonlinear interactions that can prod
uce squeezing\, the optical Kerr effect is particularly interesting becaus
e it can potentially be implemented in a wide variety of materials and arr
angements. It does not require phase matching\, and one can use optical wa
veguides to achieve long interaction lengths. The amount of squeezing can
reach significant levels due to the tight confinement in the fibres (and t
hus high intensity). However\, the advantages of generating bright squeeze
d states in third-order nonlinear media are somewhat masked by difficultie
s in using them for applications such as interferometry\, because the unce
rtainty distribution in phase\nspace for these states is tilted with respe
ct to both phase and amplitude quadrature. In this talk\, we review variou
s techniques for generating squeezed light in optical waveguides (and in p
articular optical fibres)\, and discuss a novel approach to overcome diffi
culties in applying Kerr-squeezed light to quantum-enhanced interferometry
. One popular approach to work with the Kerr-squeezed tilted states is to
create a polarisation-squeezed state by combining two such states in ortho
gonal polarisations of the same spatial mode. In a polarisation squeezed s
tate the fluctuations of a particular Stokes parameter are smaller than in
a coherent state with the same mean polarisation state. In such setups\,
it is important to use pulsed light and to protect the polarisation modes
from cross-Kerr interaction by temporally separating the pulses. This can
be done efficiently and in a very stable manner using polarisation-maintai
ning fibres and/or polarisation-sensitive group delay compensators. We rep
ort on a very stable approach to build an all-fiber setup for the generati
on of Kerr-squeezed light states based on polarisation-maintaining silica
fibers [1]\, and on a demonstration of interferometric sensitivity enhance
ment beyond the shot noise limit using these states [2]. We also present t
he first experimental observation of squeezed light generation in chalcoge
nide fibres. Chalcogenide glass fibres have 3-5 orders of magnitude higher
nonlinearity than standard\nsilica fibres. They also exhibit a wide range
of mid-IR transparency. This stimulates the study of chalcogenide (and ot
her soft highly nonlinear glasses such as tellurite) as it promotes the\nd
evelopment of non-classical light sources in an extended wavelength range
that is not readily accessible with current technologies. In the talk we a
lso discuss some aspects of numerical modelling and optimisation [3] of sq
ueezed light generation in nonlinear waveguides made of different material
s (silica\, soft tellurite and chalcogenide glasses)\, paying special atte
ntion to parasitic effects such as Raman scattering.\n\n[1] N. Kalinin\, T
. Dirmeier\, A. A. Sorokin\, E. A. Anashkina\, L. L. Sánchez‐Soto\, J.
F. Corney\, G. Leuchs\, and A. V. Andrianov\, "Observation of Robust Polar
ization Squeezing via the Kerr Nonlinearity in an Optical Fiber\," Adv Qua
ntum Tech 6(3)\, 2200143 (2023).\n\n[2] N. Kalinin\, T. Dirmeier\, A. A. S
orokin\, E. A. Anashkina\, L. L. Sánchez-Soto\, J. F. Corney\, G. Leuchs\
, and A. V. Andrianov\, "Quantum-enhanced interferometer using Kerr squeez
ing\," Nanophotonics 12(14)\, 2945–2952 (2023).\n\n[3] A. V. Andrianov\,
N. A. Kalinin\, A. A. Sorokin\, E. A. Anashkina\, L. L. Sánchez-Soto\, J
. F. Corney\, and G. Leuchs\, "Optimizing the generation of polarization s
queezed light in nonlinear optical fibers driven by femtosecond pulses\,"
Opt. Express 31(1)\, 765 (2023).\n
LOCATION:https://researchseminars.org/talk/QOART/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:C.H. Raymond Ooi
DTSTART:20240907T120000Z
DTEND:20240907T133000Z
DTSTAMP:20260422T212725Z
UID:QOART/32
DESCRIPTION:Title: C
orrelated Raman photon pairs and finite-temperature quantum memory\nby
C.H. Raymond Ooi as part of Quantum Optics and Related Topics\n\n\nAbstra
ct\nQuantum communication technology would need a reliable quantum system
for quantum information storage. Many studies of optical quantum memory in
volve the Raman scheme for writing and reading of optical pulses and singl
e photons that carry quantum information. Optical quantum memory is an ess
ential component in quantum information technology\, particularly for secu
re long-distance quantum communication networks. Many quantum memory schem
es have been proposed and demonstrated experimentally but there are limita
tions\, especially with regard to practicality and scalability. We will di
scuss our work towards room temperature quantum memory which has been rega
rded as formidable due to the rapid decoherence and broadened absorption/e
mission peaks. Counter-propagating laser schemes can be applied to achieve
optimal performances by overcoming these problems. This would be a step f
orward to realizing a practical quantum network. \n\nWe will discuss the
use of Heisenberg-Langevin-Maxwell coupled equations to study quantum corr
elations and relative squeezing of Raman photon pairs for forward and back
ward propagating gemetries with arbitrary pump and control lasers using do
uble Raman scheme. We generalized the quantum theory of stimulated Raman s
cattering to study the spatial-temporal dynamics of photons during storage
and retrieval stages of quantum memory with all dissipative mechanisms in
cluded\, such as atomic motion\, collisions and radiation baths. We will d
iscuss the effects of controllable laser pulses\, velocity distribution an
d atomic initial conditions (like atomic frequency comb). Our study involv
es numerical solutions of Heisenberg-Langevin-Maxwell coupled equations ge
neralized analytical solutions that can be used to study the quantum memor
y performance like storage time\, efficiency and the correlations between
storage and retrieval photons.\n
LOCATION:https://researchseminars.org/talk/QOART/32/
END:VEVENT
BEGIN:VEVENT
SUMMARY:O.V. Lychkovskiy
DTSTART:20240907T134000Z
DTEND:20240907T151000Z
DTSTAMP:20260422T212725Z
UID:QOART/33
DESCRIPTION:Title: M
any-body correlation functions by the recursion method: symbolic nested co
mmutators\, universal operator growth hypothesis and pseudomode expansion<
/a>\nby O.V. Lychkovskiy as part of Quantum Optics and Related Topics\n\n\
nAbstract\nRecursion method is a technique to solve coupled Heisenberg equ
ations in a tridiagonal operator basis constructed via Lanczos algorithm.
We report an implementation of the recursion method that addresses quantu
m many-body dynamics in the nonperturbative regime. The implementation has
three key ingredients: a computer-algebraic routine for symbolic calculat
ion of nested commutators\, a procedure to extrapolate the sequence of Lan
czos coefficients according to the universal operator growth hypothesis an
d the pseudomode expansion addressing the large time asymptotics. We apply
the method to calculate infinite-temperature correlation functions for sp
in-1/2 systems on one- and two-dimensional lattices. The method allows one
to accurately calculate transport coefficients. As an illustration\, we c
ompute the diffusion constant for the transverse-field Ising model on a sq
uare lattice. The talk is based on arXiv 2401.17211\, 2407.12495. \n\nThe
research is supported by the Russian Science Foundation under the grant No
. 24-22-00331.\n
LOCATION:https://researchseminars.org/talk/QOART/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:L.C. Kwek
DTSTART:20240908T070000Z
DTEND:20240908T073000Z
DTSTAMP:20260422T212725Z
UID:QOART/34
DESCRIPTION:Title: I
ntegrated Silicon Photonics\nby L.C. Kwek as part of Quantum Optics an
d Related Topics\n\n\nAbstract\nQuantum and classical neural networks with
integrated photonics have recently emerged as a promising approach toward
s efficient and high-performance information processing. By harnessing the
unique features of photons\, such as their quantum nature\, ecofriendline
ss or high-speed characteristics\, these integrated systems have been appl
ied to optical neural network and boson sampling. We report recent work do
ne in this direction.\n
LOCATION:https://researchseminars.org/talk/QOART/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:T. Qureshi
DTSTART:20240908T074000Z
DTEND:20240908T091000Z
DTSTAMP:20260422T212725Z
UID:QOART/35
DESCRIPTION:Title: G
eneralized Two-Particle Interference\nby T. Qureshi as part of Quantum
Optics and Related Topics\n\n\nAbstract\nTwo-photon interference is an in
teresting quantum phenomenon that is usually captured in two distinct type
s of experiments\, namely the Hanbury-Brown-Twiss (HBT) experiment and the
Hong-Ou-Mandel (HOM) experiment. First\, a duality relation\, between the
particle distinguishability and the visibility of two-particle interferen
ce\, is derived. The distinguishability of the two particles\, arising fro
m some internal degree of freedom\, puts a bound on the sharpness of the t
wo-particle interference they can produce\, in a HOM or HBT kind of experi
ment. This points to a common origin of both the experiments which are gen
erally considered distinct. Then a generalized formulation of two-particle
interference is presented. The HOM and the HBT effects emerge as special
cases in the general analysis. A two-particle interference experiment\, wh
ich is intermediate between the two effects\, is proposed and analyzed. Th
us two-particle interference is shown to be a single phenomenon with vario
us possible implementations\, including the HBT and HOM setups.\n
LOCATION:https://researchseminars.org/talk/QOART/35/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. Rai
DTSTART:20240908T092000Z
DTEND:20240908T110000Z
DTSTAMP:20260422T212725Z
UID:QOART/36
DESCRIPTION:Title: Q
uantum Physics with integrated waveguide arrays\nby A. Rai as part of
Quantum Optics and Related Topics\n\n\nAbstract\nWithin the last few years
\, lattices of evanescently coupled optical waveguides have proven to be a
versatile platform for investigating a variety of quantum effects. The po
ssibility of engineering various interactions by design makes these arrays
an experimentally accessible tool for studying a variety of effects from
a large number of fields of physics. Another salient feature of this syste
m is the possibility of controlling the exact initial conditions for the l
ight propagating inside the array. Moreover\, the decoherence rate in this
system is very low\, even for longer propagation distances. In this talk\
, we present a summary of some of our studies on optical waveguide arrays.
\n
LOCATION:https://researchseminars.org/talk/QOART/36/
END:VEVENT
BEGIN:VEVENT
SUMMARY:I. I. Dzhadan
DTSTART:20240908T120000Z
DTEND:20240908T123000Z
DTSTAMP:20260422T212725Z
UID:QOART/37
DESCRIPTION:Title:
Многофтонная запутанность\nby I. I. Dzhadan as
part of Quantum Optics and Related Topics\n\n\nAbstract\nПроанали
зированы особенности передачи информац
ии через закрытые каналы на основе много
фотонной запутанности. Важным преимущес
твом таких каналов является возможность
дополнительного шифрования сообщений к
лассическим ключом нумерации каналов. Н
а примере многоканального квантового тр
анслятора с шифроключом рассмотрена каж
ущаяся передача информации "в прошлое". П
оказано\, что такое "ретрокаузальное" дей
ствие не приводит к нарушению классичес
кой причинности и находит свои параллел
и в физике и других дисциплинах.\n
LOCATION:https://researchseminars.org/talk/QOART/37/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kh. Sh. Meretukov
DTSTART:20240908T123000Z
DTEND:20240908T130000Z
DTSTAMP:20260422T212725Z
UID:QOART/38
DESCRIPTION:Title: N
onlinear equations in open quantum systems\nby Kh. Sh. Meretukov as pa
rt of Quantum Optics and Related Topics\n\n\nAbstract\nThis report present
s the kinetic equation for the mean values obtained by the method of time-
dependent projective operators. This equation is applied to the Kerr model
. For this system\, a closed system of differential equations for the aver
ages from the creation and annihilation operators and their squares is obt
ained. 2 regimes of the system are considered: without external field and
with small external field. For the 1st regime\, the obtained results are c
ompared with analytical results\n
LOCATION:https://researchseminars.org/talk/QOART/38/
END:VEVENT
BEGIN:VEVENT
SUMMARY:D.V. Kupriyanov
DTSTART:20240908T130000Z
DTEND:20240908T134000Z
DTSTAMP:20260422T212725Z
UID:QOART/39
DESCRIPTION:Title: R
adiative Coupling of a Multilevel Atom with a Dielectric Structure\nby
D.V. Kupriyanov as part of Quantum Optics and Related Topics\n\n\nAbstrac
t\nThe coupling of quantum emitters\, such as cold atoms\, with nanoscale
structures like dielectric waveguides and subwavelength resonators brings
new opportunities for quantum technology. The directional emission of indi
vidual photons could create certain conditions for a quantum computer inte
rface based on neutral atoms. Prototypes of similar nanophotonic devices h
ave been already demonstrated in experiments involving the confinement of
atoms within microresonators\, photonic crystal structures\, and nanofiber
s [1]. We propose a microscopic scheme for calculating radiation correctio
ns to the energy spectrum of a single-electron atom in the presence of a n
anoscale dielectric object. The calculation takes into account the complet
e Zeeman structure of an isolated atomic transition and can be applied to
systems with arbitrary geometric configurations. At the studied frequencie
s\, the dielectric properties can be replicated by replacing the bulk mate
rial with an ensemble of two-level atoms with resonant transition frequenc
ies being offset from the radiation frequency of a reference atom [2]. We
demonstrate the approach by applying it to various nanostructure geometrie
s used in the experiments [3] and conduct a comparative analysis to demons
trate the advantages of exciting an atom at frequencies close to the edge
of the Brillouin zone in asymmetric photonic crystals. Figure 1 demonstrat
es spectral parameters of the caesium-133 atom placed near the one-dimensi
onal asymmetric photonic crystal. Quasi-energy sublevels exhibit twofold d
egeneracy and non-orthogonality between states from different energy level
s\, which we show is connected to the nontrivial axial symmetry in atomic
excitation and decay channels. The observed increase in atomic decay rate
is accompanied by its directional radiation into a waveguide mode\, which
is significant for developing quantum interfaces based on individual atoms
and photons. Due\nto this radiation\, a resonant scattering channel can b
e used to create a chain of entangled atoms. The phase of the atomic state
changes by 180 degrees during the resonant scattering of photons\, that i
s a critical aspect of the C-Z entanglement protocol\, a promising scheme
proposed as an alternative to the Rydberg blockade protocol.\n\nAcknowledg
ements: The work was funded by the Russian Science Foundation (Project No.
23-72-10012).\n\nReferences\n\n[1] D E Chang\, J S Douglas\, A González-
Tudela\, C-L Hung and H J Kimble\, Rev. Mod. Phys. 90\, 031002 (2018)\n\n[
2] N A Moroz\, L V Gerasimov\, A D Manukhova and D V Kupriyanov\, Phys. Re
v. 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 Bench
eikh\, J Laurat and C Sauvan\, Opt. Express 30\, 45093 (2022)\n
LOCATION:https://researchseminars.org/talk/QOART/39/
END:VEVENT
BEGIN:VEVENT
SUMMARY:I.V. Volovich
DTSTART:20240909T060000Z
DTEND:20240909T073000Z
DTSTAMP:20260422T212725Z
UID:QOART/40
DESCRIPTION:Title: O
n the Absence of Bell-CHSH Inequality Violations at Large Distances\nb
y I.V. Volovich as part of Quantum Optics and Related Topics\n\n\nAbstract
\nThe standard derivation of Bell-type inequality violations is typically
applied only to scenarios involving short distances between detectors. Thi
s conventional approach often overlooks the dependence of quantum mechanic
al wave functions on space-time variables. In this study\, we examine the
behavior of entangled photons produced in spontaneous parametric downconve
rsion (SPDC) experiments and demonstrate that Bell-CHSH inequalities are n
ot violated at large distances. We analyze the propagation of entangled ph
oton wave packets and show that these initially entangled states tend to d
isentangle over large spacelike separations. This finding aligns with the
observed violations of Bell inequalities at shorter detector separations.
To further explore this phenomenon\, we propose an experiment to investiga
te how the quantum correlation function and Bell values change with increa
sing detector distance\, predicting that these quantities will decrease in
versely with distance.\nOn the absence of violation of Bell-CHSH inequalit
ies at large distances.\n
LOCATION:https://researchseminars.org/talk/QOART/40/
END:VEVENT
BEGIN:VEVENT
SUMMARY:G.N. Goltsman
DTSTART:20240909T074000Z
DTEND:20240909T084000Z
DTSTAMP:20260422T212725Z
UID:QOART/41
DESCRIPTION:Title: S
uperconducting single photon detector: research and applications\nby G
.N. Goltsman as part of Quantum Optics and Related Topics\n\n\nAbstract\nD
uring last twenty years\, a new generation of superconducting detectors ba
sed on hot-electron-phenomena was developed. These sensors have already de
monstrated performance that makes them devices-of-choice for many terahert
z\, infrared and optical applications. The development of compact helium-f
ree cryocoolers together with effective sources of terahertz\nand infrared
radiation greatly expanded the field of application of superconducting de
tectors including astronomy\, medicine\, security and quantum communicatio
ns\, and made them friendly in use. To date\, due to the growing interest\
, the market for superconducting devices is gradually expanding\, as evide
nced by the emergence of small companies engaged in the development\, impr
ovement and commercialization of superconducting devices. \nOne such devic
e is the superconducting nanowire single-photon detector (SNSPD or SSPD).
SNSPDs combine high detection efficiency\, low dark count rate\, and high
temporal resolution in a single device in visible and near IR range. SNSPD
s have been successfully employed for classical and quantum optics applica
tions ranging from optical time domain reflectometry (OTDR)\, light detect
ion and ranging (LiDAR)\, space-to-ground communications\, quantum dot pho
tonics\, quantum key distribution to experiments with indistinguishable an
d entangled photon pairs and applications in the life sciences. \nFew year
s ago\, a fully integrated circuit including a single photon source (carbo
n nanotube)\, detectors (SNSPDs) and Si3N4 waveguides has already been imp
lemented on a chip. Going beyond such proof-of-principle concepts\, the re
alization of large scale QPICs is expected to have profound impact on scie
nce and technology\, material engineering\, as well as quantum information
processing including quantum computing\, simulation and metrology.\nIt ha
s recently been shown that the nanosize of the current-carrying strip is n
ot a necessary attribute for single-photon detection. Using a kinetic-equa
tion approach\, the dynamics of electrons and phonons in current-carrying
superconducting strip with a current close to the depairing current after
the absorption of a single photon of the near-infrared or optical range wa
s studied. Second\, it has been experimentally demonstrated that single-ph
oton detection is indeed achieved in micrometer-wide NbN bridges biased by
a direct current close to the experimental critical current\, which is es
timated to be at least 50% of the theoretically expected depairing current
. These results offer an alternative to the standard superconducting singl
e-photon detectors\, based on nanometer-scale nanowires implemented in a l
ong meandering structure. The results are consistent with improved theoret
ical modeling based on the theory of nonequilibrium superconductivity\, in
cluding the vortex-assisted mechanism of initial dissipation. To think abo
ut practical devices\, we choose to work with wide wires fabricated with p
hotolithography rather than narrower wires commonly fabricated with e-beam
lithography. These wider wires consume more area\, which is problematic i
n large integrated systems. We find that elimination of even a\nsingle e-b
eam lithography step greatly simplifies fabrication process. \nFurther dev
elopment of SSPDs associated with the implementation of complex integrated
photonic (PICs) and quantum photonic integrated circuits (QPICs) on a sin
gle chip. Integrated circuits are resistant to mechanical vibrations and t
emperature fluctuations\, they do not require long alignment procedure and
can be easily scaled. To date\, integrated SNSPDs have been implemented o
n various material platforms\, such as silicon on insulator (SOI)\, galliu
m arsenide (GaAs)\, silicon nitride (Si3N4) and polycrystalline diamond. E
ach platform has its advantages and disadvantages\, so further development
takes place in parallel. Despite the fact that all the building blocks fo
r a fully-functional QPIC\, including single-photon sources\, detectors an
d passive circuits\, have been demonstrated\, full integration of all the
components on a single chip is still a somewhat challenging and complicate
d task.\n
LOCATION:https://researchseminars.org/talk/QOART/41/
END:VEVENT
BEGIN:VEVENT
SUMMARY:E.O. Kiktenko
DTSTART:20240909T092000Z
DTEND:20240909T110000Z
DTSTAMP:20260422T212725Z
UID:QOART/42
DESCRIPTION:Title: Q
uantum computing with qudits\nby E.O. Kiktenko as part of Quantum Opti
cs and Related Topics\n\n\nAbstract\nRecent progress in a development of q
uantum computing platforms operating with qudits (d-dimensional quantum pa
rticles with d>2) rises important questions of how such platforms can be u
sed in the most efficient way for implementing known quantum algorithms. I
n my presentation\, I will be discussing possible approaches for the imple
mentation of qubit-based circuits using qudit-based hardware. These approa
ches include: (i) employing higher-level qudits to substitute ancillary qu
bits in the decomposition of multiqubit gates\, (ii) embedding the computa
tional space of multiple qubits into a single qudit\, and (iii) combining
approaches (i) and (ii). Special attention will be paid to the possible ex
perimental implementation of the discussed approaches within the systems o
f superconducting qubits and trapped ion qudits.\n
LOCATION:https://researchseminars.org/talk/QOART/42/
END:VEVENT
BEGIN:VEVENT
SUMMARY:G.G. Amosov
DTSTART:20240909T120000Z
DTEND:20240909T130000Z
DTSTAMP:20260422T212725Z
UID:QOART/43
DESCRIPTION:Title: O
n a generalized approach to quantum tomography via projective unitary repr
esentations of groups\nby G.G. Amosov as part of Quantum Optics and Re
lated Topics\n\n\nAbstract\nSuppose that $\\mathfrak {M}$ is a positive op
erator-valued measure on a measurable space $X$ with values in the set of
all positive bounded operators\n$B(H)_+$ in a separable Hilbert space $H$.
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 $x\\in X \\to g
x\\in X\,\\ g\\in G$\, then $\\mathfrak M$ is said to be covariant with re
spect to $\\mathcal {U}=\\{U_g\,\\ g\\in G\\}$ under the condition $U_g\\m
athcal {M}(B)U_g^*=\\mathfrak {M}(gB)$ for all measurable subsets $B\\subs
et X$ and $g\\in G$. In quantum tomography theory we use a set of function
s instead of a density operator $\\rho $. Using a covariant POVM $\\mathfr
ak M$ equipped with a projective unitary representation $\\mathcal U$ we c
an 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 $\\rho $\, w
hile the second one is associated with a measurement of $\\rho $ by $\\mat
hfrak {M}$. We attribute these two functions to homodyne and heterodyne me
asurements and discuss the connection between them.\n
LOCATION:https://researchseminars.org/talk/QOART/43/
END:VEVENT
BEGIN:VEVENT
SUMMARY:V.V. Dodonov
DTSTART:20240909T134000Z
DTEND:20240909T151000Z
DTSTAMP:20260422T212725Z
UID:QOART/44
DESCRIPTION:Title: Q
uantum dynamics of oscillator-like systems when some parameters change sig
ns\nby V.V. Dodonov as part of Quantum Optics and Related Topics\n\n\n
Abstract\nI shall talk about some recent results concerning the evolution
of a quantum particle in time-dependent oscillator-like potentials\, when
the frequency or its square change the sign. The main attention is given t
o the limit cases of adiabatic and fast evolutions. Applications to a char
ged particle in time-dependent magnetic fields will be discussed\, as well
.\n
LOCATION:https://researchseminars.org/talk/QOART/44/
END:VEVENT
BEGIN:VEVENT
SUMMARY:S.L. Bala
DTSTART:20240910T060000Z
DTEND:20240910T070000Z
DTSTAMP:20260422T212725Z
UID:QOART/45
DESCRIPTION:Title: R
eading-off properties about the quantized radiation field from the optical
tomogram\nby S.L. Bala as part of Quantum Optics and Related Topics\n
\n\nAbstract\nOptical tomograms are readily obtained from experimental dat
a. The tomogram is the starting point for reconstructing the density opera
tor or Wigner function. The reconstruction program is often challenging\,
particularly in the case of systems with infinite dimensional Hilbert spac
es\, as for instance in optics. It is therefore well-advised to extract as
many properties of the radiation field as possible directly from the tomo
gram avoiding detailed state reconstruction. The importance of optical tom
ograms\, and the fact that they contain all the information about the quan
tized radiation field have been highlighted in detail by different researc
h groups\, primarily from Russia. We will expand on this aspect and identi
fy certain nonclassical properties of states of light directly from qualit
ative features of appropriate optical tomograms\, and also quantify these
properties.\n
LOCATION:https://researchseminars.org/talk/QOART/45/
END:VEVENT
BEGIN:VEVENT
SUMMARY:K. Thapliyal
DTSTART:20240910T074000Z
DTEND:20240910T091000Z
DTSTAMP:20260422T212725Z
UID:QOART/46
DESCRIPTION:Title: Q
uantum 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 Glauber-Sudar
shan P-function\, do not have a classical analogue.\nThese states have pav
ed way for second quantum revolution and photonic quantum technology. A fe
w\nexamples of generation of such states in nonlinear optical processes an
d its challenges will be\ndiscussed. Photon number measurements and post-s
election make a plethora of quantum state\nengineering operations feasible
. Quantum state engineering using non-Gaussian operations provides\npowerf
ul tool for continuous variable quantum information. Practical challenges
in their\nimplementation and feasibility of generation of such states will
be discussed [1-4]. Twin beams are\ngenerated in a nonlinear optical proc
ess\, namely spontaneous parametric down conversion\, under\nstronger pump
ing. They are endowed with ideally perfect photon number correlations in t
he\nconstituting signal and idler beams. This quantum feature is revealed
by the sub-shot noise photon\nnumber correlations. However\, the marginal
signal and idler photon number distributions are\nmultimode thermal. We il
lustrate the generation of engineered multimode quantum states from twin\n
beams by photon subtraction and addition with supporting experimental real
ization. Future prospects\,\nin view of our results\, will be discussed.\n
\n[1] K. Thapliyal\, J. Peřina Jr.\, O. Haderka\, V. Michálek\, and R. M
achulka\, Experimental characterization of\nmultimode photon-subtracted tw
in beams\, Phys. Rev. Res. 6\, 013065 (2024).\n\n[2] J. Peřina Jr.\, K. T
hapliyal\, O. Haderka\, V. Michálek\, and R. Machulka\, Generalized sub-P
oissonian states of\ntwo-beam fields\, Opt. Express 32\, 537 (2024).\n\n[3
] K. Thapliyal\, J. Peřina Jr.\, O. Haderka\, V. Michálek\, and R. Machu
lka\, Experimental photon addition and\nsubtraction in multi-mode and enta
ngled optical fields\, Opt. Lett. 49\, 4521 (2024).\n\n[4] J. Peřina Jr.\
, K. Thapliyal\, O. Haderka\, V. Michálek\, and R. Machulka\, Sub-Poisson
ian twin beams\, Optica\nQuantum 2\, 148 (2024).\n
LOCATION:https://researchseminars.org/talk/QOART/46/
END:VEVENT
BEGIN:VEVENT
SUMMARY:P.R. Sharapova
DTSTART:20240910T092000Z
DTEND:20240910T102000Z
DTSTAMP:20260422T212725Z
UID:QOART/47
DESCRIPTION:Title: M
ultimode squeezing: generation and characterization\nby P.R. Sharapova
as part of Quantum Optics and Related Topics\n\n\nAbstract\nMultimode squ
eezed light is an increasingly popular tool in photonic quantum technologi
es\, including sensing\, imaging\, and computing [1]. In metrology\, it pr
ovides the measurement of the phase beyond the classical sensitivity limit
[2\,3]\, its role was crucial for the first observation of gravitational
waves [4]. At the same time\, multiple squeezed modes are promising tools
for continuous-variable quantum computing\, quantum information processing
and quantum communication\, where each mode (qumode) serves as an informa
tion carrier and a large set of modes can be used for the cluster sates ge
neration and measurement-based quantum computation [5].\nWith numerous app
lications of multimode squeezed light\, it is important to characterize sq
ueezing in multiple spatial and temporal modes taking into account interna
l losses in the system: \nWhen PDC is generated in transparent bulk nonlin
ear crystals the absorption is small enough to be neglected\, however\, in
ternal losses can be significant for structured media like waveguides\, wh
ere the guided light can be lost due to scattering from surface roughness.
\nWe investigate the mode structure of lossy broadband multimode squeezed
light and show how the maximal possible squeezing can be extracted and mea
sured. In opposite to an ideal multimode squeezed states\, where the uniqu
e basis of Schmidt modes can be found via Bloch-Messiah reduction of Bogol
iubov transformation [6]\, the broadband basis of Schmidt modes for lossy
squeezed states cannot be uniquely defined. We introduce a new type of bro
adband basis for lossy systems in which the squeezing is maximized\, i.e.\
, the upper bound for squeezing is reached\, and show how these modes can
be constructed [7].\nFurthermore\, the existing experimental methods of mu
ltimode squeezed vacuum characterization (homodyne detection\, projective
filtering) are technically complicated\, and in the best case\,\ndeal with
a single mode at a time. We present a method [8] based on a cascaded syst
em of nonlinear crystals to simultaneously measure squeezing in different
spatial modes. In such a system\, the second crystal serves as an amplifie
r/deamplifier for the squeezed light generated in the first crystal (squee
zer). The direct intensity measurement of light after the amplifier allows
us to reconstruct the squeezing of the light generated in the first cryst
al.\n\n[1] U. L. Andersen\, T. Gehring\, C. Marquardt\, and G. Leuchs\, Ph
ys. Scr. 91 053001 (2016).\n\n[2] V. Giovannetti\, S. Lloyd\, and L. Macco
ne\, 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. Abbott 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. Neergaar
d-Nielsen\, U. L. Andersen\, Science 366\, 6463 (2018).\n\n[6] M. G. Rayme
r and I. A. Walmsley\, Phys. Scripta 95\, 064002 (2020).\n\n[7] D. A. Kopy
lov\, T. Meier\, P. R. Sharapova\, arXiv:2403.05259 (2024).\n\n[8] I. Bara
kat\, M. Kalash\, D. Scharwald\, P. R. Sharapova\, N. Lindlein\, M. V. Che
khova\, arXiv:2402.15786 (2024).\n
LOCATION:https://researchseminars.org/talk/QOART/47/
END:VEVENT
BEGIN:VEVENT
SUMMARY:I.V. Ermakov
DTSTART:20240910T120000Z
DTEND:20240910T133000Z
DTSTAMP:20260422T212725Z
UID:QOART/48
DESCRIPTION:Title: P
olynomially restricted operator growth in dynamically integrable models\nby I.V. Ermakov as part of Quantum Optics and Related Topics\n\n\nAbstr
act\nWe provide a framework to determine the upper bound to the complexity
of a computing a given observable with respect to a Hamiltonian. By consi
dering the Heisenberg evolution of the observable\, we show that each Hami
ltonian defines an equivalence relation\, causing the operator space to be
partitioned into equivalence classes. Any operator within a specific clas
s never leaves its equivalence class during the evolution. We provide a me
thod to determine the dimension of the equivalence classes and evaluate it
for various models\, such as the XY chain and Kitaev model on trees. 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 suppre
ssed relaxation of qubits near the boundary. Our methods are used to revea
l several new cases of simulable quantum dynamics\, including a XY-ZZ mode
l which cannot be reduced to free fermions.\n
LOCATION:https://researchseminars.org/talk/QOART/48/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.N. Pechen
DTSTART:20240910T134000Z
DTEND:20240910T151000Z
DTSTAMP:20260422T212725Z
UID:QOART/49
DESCRIPTION:Title: P
henomenon of a stronger trapping behaviour in $\\Lambda$-type quantum syst
ems and quantum control landscapes\nby A.N. Pechen as part of Quantum
Optics and Related Topics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/QOART/49/
END:VEVENT
BEGIN:VEVENT
SUMMARY:R.-K. Lee
DTSTART:20240911T060000Z
DTEND:20240911T073000Z
DTSTAMP:20260422T212725Z
UID:QOART/50
DESCRIPTION:Title: M
achine-learning enhanced quantum state tomography and its applications for
optical cat states\nby R.-K. Lee as part of Quantum Optics and Relate
d Topics\n\n\nAbstract\nWith this talk\, I will first illustrate the imple
mentation of our machine-learning (ML) enhanced quantum state tomography (
QST) for continuous variables\, through the experimentally measured data g
enerated from squeezed vacuum states [1]\, as an example of quantum machin
e learning [2]. Our recent progress will be demonstrated in applying such
a ML-QST on Wigner currents [3]\, single-photon Fock state [4]\, optical c
at state [5]\, Bayesian estimation for gravitational wave detectors [6\,
7]\, and quantumness measure [8].\n\n[1] Hsien-Yi Hsieh\, et al.\, "Extrac
t the Degradation Information in Squeezed States with Machine Learning\,"
Phys. Rev. Lett. 128\, 073604 (2022).\n\n[2] Alexey Melnikov\, Mohammad K
ordzanganeh\, Alexander Alodjants\, and RKL\," Quantum Machine Learning: f
rom physics to software engineering\," Adv. in Phys. X (Review Article) 8\
, 2165452 (2023).\n\n[3] Yi-Ru Chen\, et al.\, "Experimental reconstructio
n 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 st
ate tomography\," revised to Phys. Rev. A (2024)\; [arXiv: 2405.02812].\n
\n[5] Yi-Ru Chen\, et al.\, "Generation of heralded optical `Schroedinger
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] Y
uhang Zhao\, et al.\, "Frequency-dependent squeezed vacuum source for broa
dband quantum noise reduction in advanced gravitational-wave detectors\,"
Phys. Rev. Lett. 124\, 171101 (2020)\; Editors' Suggestion\; Featured in
Physics.\n\n[8] Ole Steuernagel and RKL\, "Quantumness Measure from Phase
Space Distributions\," [arXiv: 2311.17399].\n
LOCATION:https://researchseminars.org/talk/QOART/50/
END:VEVENT
BEGIN:VEVENT
SUMMARY:D.B. Yusupov
DTSTART:20240911T074000Z
DTEND:20240911T081000Z
DTSTAMP:20260422T212725Z
UID:QOART/51
DESCRIPTION:Title: Q
uasi-Phase Matching in Nonlinear Optics\nby D.B. Yusupov as part of Qu
antum Optics and Related Topics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/QOART/51/
END:VEVENT
BEGIN:VEVENT
SUMMARY:S.A. Moiseev
DTSTART:20240911T081000Z
DTEND:20240911T091000Z
DTSTAMP:20260422T212725Z
UID:QOART/52
DESCRIPTION:Title: P
hoton echo protocols of optical quantum memory\nby S.A. Moiseev as par
t of Quantum Optics and Related Topics\n\n\nAbstract\nThe main properties
of the conventional photon echo quantum memory protocols are analyzed and
the results of recent experiments are discussed. The distinctive features
of the effect of spectral dispersion and nonlinear interaction of light p
ulses with resonant atoms on the quantum storage of broadband signal pulse
s in the studied echo protocols are identified and discussed. Using the p
hoton echo area theorem\, closed analytical solutions for quantum memory e
cho protocols are obtained\, describing the storage of weak and intense si
gnal pulses\, allowing us to find conditions for the implementation of hig
h efficiency in echo protocols with strong nonlinear interaction of signal
and control pulses with atoms. The key existing practical problems and wa
ys to solve them in realistic experimental conditions are described. Final
ly\, new optical quantum memory protocols based on the use of long-lived m
acroscopic quantum coherence are also proposed and their advantages are di
scussed.\n
LOCATION:https://researchseminars.org/talk/QOART/52/
END:VEVENT
BEGIN:VEVENT
SUMMARY:O.V. Man'ko
DTSTART:20240911T092000Z
DTEND:20240911T110000Z
DTSTAMP:20260422T212725Z
UID:QOART/53
DESCRIPTION:Title: P
robability representation for quantum states on examples of oscillator and
qubit\nby O.V. Man'ko as part of Quantum Optics and Related Topics\n\
n\nAbstract\nIn conventional formulation of quantum mechanics system state
s are described by wave functions\, density operators and their representa
tions as the Wigner function\, the Husimi function\, the Glauber-Sudarshan
function. Many decades (practically century) the idea to construct usual
probability distributions to describe the states of quantum systems was no
t realized. Only recently such probability distribution representation for
quantum states was constructed for all systems. The spin (qudit) states a
re described by conditional probability distribution w(X|j) and oscillator
states are described by quantum tomograms (symplectic tomographic probabi
lity distribution function). In the talk explicit expressions for these pr
obabilities are given. The tomograms describing oscillator states are give
n by Gaussian probability distributions which contain all information abou
t usual wave functions of the states and density matrices of the state. Tw
o qubit states are described by conditional probabilities and usual densit
y matrices of quantum states are expressed in terms of these probabilities
. The Schrödinger equation for wave function is mapped onto kinetic equat
ion for the introduced probability distributions. The general approach for
quantization based on the formalism of star-product of functions-symbols
of operators is reviewed.\n
LOCATION:https://researchseminars.org/talk/QOART/53/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.S. Trushechkin
DTSTART:20240911T120000Z
DTEND:20240911T133000Z
DTSTAMP:20260422T212725Z
UID:QOART/54
DESCRIPTION:Title: Q
uantum communication networks with bipartite entanglement sources\nby
A.S. Trushechkin as part of Quantum Optics and Related Topics\n\n\nAbstrac
t\nQuantum networks attract much interest now. One of obvious purposes of
quantum networks is secure communications. The usual quantum key distribut
ion (QKD) deals with bipartite communication\, but scaling of QKD to netwo
rk solutions is developed now. In the first part of the talk\, we will con
sider networks of users connected by bipartite QKD links. Such networks al
ready exist. A problem arises: Having a network of bipartite QKD links\, h
ow to generate a conference key at maximal rate? An optimal solution is gi
ven by a spanning-tree-packing protocol for conference key propagation.\n\
nThe second part of the talk will be devoted to foreseeable future quantum
networks with bipartite entanglement sources. Such networks provide more
possibilities and problems to be considered. The problem of conference key
distribution is still relevant for these networks (but with more possibil
ities). A fully quantum counterpart of this problem is the Greenberger-Hor
ne-Zeilinger (GHZ) multipartite entangled state distillation. GHZ states f
ind many cryptographic\, metrologic and computational applications. Spanni
ng tree packing protocol also can be used for GHZ distillation and is also
optimal whenever the distributed bipartite entangled states are pure. For
general (mixed) bipartite quantum states\, we present fundamental bounds
on the conference key distribution and GHZ distillation rates for such net
works.\n
LOCATION:https://researchseminars.org/talk/QOART/54/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.V. Sergienko
DTSTART:20240911T134000Z
DTEND:20240911T151000Z
DTSTAMP:20260422T212725Z
UID:QOART/55
DESCRIPTION:Title: D
irectionally unbiased linear optics enable novel high-resolution sensors a
nd quantum network routers\nby A.V. Sergienko as part of Quantum Optic
s and Related Topics\n\n\nAbstract\nGrover multiports are higher-dimension
al generalizations of beam splitters in which inputs to any of the four po
rts have an equal probability of exiting at any of the four ports\, includ
ing the input port. This offers direct access to a greater number of degre
es of freedom [1]: We demonstrate that traditional interferometers can obt
ain novel features when directionally unbiased multi-ports replace traditi
onal beam splitters. It will be shown that the Grover-based counterpart of
the conventional Michelson interferometer can substantially enhance the p
hase measurement resolution.\nThe Grover-Michelson interferometer demonstr
ates a tunable intensity-phase slope instead of a traditional fixed cos2 p
rofile\, thus enabling super-resolution phase measurement while utilizing
only linear optical elements and classical states of light [2].\nThe tradi
tional two-photon Hong-Ou-Mandel (HOM) effect could be expanded onto a hig
herdimensional set of four spatial modes when combining the Grover coin wi
th quantum-correlated twophoton input and coincidence measurements. We int
roduce a novel quantum photonic state router design that allows controllab
le redistribution (switching) of (|2\,0>+|0\,2>) quantum states over these
four modes using directionally unbiased linear-optical four-ports without
post-selection [3]. The original HOM effect only enables photon pairs to
exit in two directions in space. However\, when beam splitters and phase s
hifters accompany the Grover coin\, the result is a directionally controll
able two-photon HOM effect in four spatial modes\, with the outgoing photo
n direction controlled by changing the phases in the system. By this means
\, spatial and temporal control of the propagation of the two-photon super
position state through a network or quantum nodes (quantum state routing)
can be achieved.\n\n[1] Shuto Osawa\, David S. Simon\, and Alexander V. Se
rgienko "Directionally-Unbiased Unitary Optical Devices in Discrete-Time Q
uantum Walks\,” Entropy\, v. 21\, p. 853 (2019).\n\n[2] Christopher R. S
chwarze\, David S. Simon\, and Alexander V. Sergienko\,'' Enhanced-Sensiti
vity Interferometry With Phase-Sensitive Unbiased Multiports\,” Phys. Re
v. A 107\, 052615 (2023)\n\n[3] Shuto Osawa\, David S. Simon\, and Alexand
er V. Sergienko "Higher-Dimensional Hong-Ou-Mandel Effect and State Redist
ribution With Linear-Optical Multiports\,” Phys. Rev. A 102\, 063712 (20
20).\n
LOCATION:https://researchseminars.org/talk/QOART/55/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A.L. Sokolov
DTSTART:20240909T152000Z
DTEND:20240909T162000Z
DTSTAMP:20260422T212725Z
UID:QOART/56
DESCRIPTION:Title:
Пучки с осесимметричной поляризационно
й структурой\nby A.L. Sokolov as part of Quantum Optics and
Related Topics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/QOART/56/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A. E. Teretenkov
DTSTART:20240911T152000Z
DTEND:20240911T153000Z
DTSTAMP:20260422T212725Z
UID:QOART/57
DESCRIPTION:Title: C
losing\nby A. E. Teretenkov as part of Quantum Optics and Related Topi
cs\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/QOART/57/
END:VEVENT
END:VCALENDAR