Speaker: Dr. Jhen-Dong Lin (invited speaker)
Title: Non-Markovian Quantum Exceptional Points
Affiliations:
1Department of Physics, National Cheng Kung University, 701
Tainan, Taiwan
2Center for Quantum Frontiers of Research
Technology, NCKU,
70101 Tainan, Taiwan
Abstract: Exceptional points (EPs) are singularities in the
spectra of non-Hermitian operators, where eigenvalues and
eigenvectors coalesce. Recently, open quantum systems have been
increasingly explored as testbeds for quantum EPs due to their
natural non-Hermitian nature. However, existing works mostly focus
on the Markovian limit, leaving a gap in understanding EPs in the
non-Markovian regime. In this work, I will present our new
results, where we address this gap by proposing a theoretical
framework based on two numerically exact descriptions of
non-Markovian dynamics: the pseudomode mapping and the
hierarchical equations of motion. We unveil pure non-Markovian EPs
that are unobservable in the Markovian limit. Remarkably, the EP
aligns with the Markovian-to-non-Markovian transition. Moreover,
we show that structured environments can elevate EP order, thereby
enhancing the system's sensitivity.
Speaker: Prof. Wiesław Leoński (invited speaker)
Authors: W. Leoński1, J. K. Kalaga1, A. Kowalewska-Kudłaszyk2 and J. Perina Jr.3
Title: Two-mode entangled bosonic system and Legget-Garg inequality
Affiliations:
1Quantum Optics and Engineering Division, Institute of Physics, University of Zielona Góra, Zielona Góra, Poland
2Nonlinear Optics Division, ISQI, Faculty of Physics, A. Mickiewicz University, Poznan, Poland
3Joint Laboratory of Optics, Faculty of Science, Palacký University, Olomouc, Czech Republic
Abstract: [PDF] We consider a system involving two
quantum nonlinear oscillators mutually coupled and continuously
driven by an external coherent field. For such a model, we discuss
temporal correlations. In particular, we examine the Leggett-Garg
inequality's (LGI) violation. We analyze various scenarios of
measurements based on projection onto different Bell states,
showing that the possibility of violating LGI inequalities is
related to the use of different projectors.
Speaker: Prof. Zbigniew Ficek (invited speaker)
Title: Controlled generation of coherence and entanglement in a
three-mode system
Affiliation: Quantum Optics and Engineering Division, Institute of
Physics, University of Zielona Góra, Zielona Góra, Poland
Abstract: We investigate a method for a controlled generation of
coherence and entanglement in a three-mode system with closed-loop
coupling between the modes. We assume that two of the three
possible coupling channels are of the squeezing-type, whereas the
remaining is a beam-splitter type. The results show that the
competition between the induced coherence and the already existing
coherence in the beam-splitter type coupling channel leads to
phase dependent oscillations of the maximal entanglement generated
the other channels. In other words, generated entanglement in the
system can be phase controlled and completely transferred to a
given pair of modes.
Speaker: Prof. Artur Barasiński (invited speaker)
Title: Efficient and Reliable Detection of Nonlocal Quantum
Correlations via Random Measurements
Affiliation: Institute of Theoretical Physics, University of
Wrocław, 50-204 Wrocław, Poland
Abstract: We present a comprehensive numerical analysis exploring
violations of local realism across various non-equivalent models
of local hidden variables. Specifically, we delve into a recently
proposed operational measure of nonlocality, which assesses both
the probability of violating local realism under randomly sampled
observables and the strength of such violation in the face of
white noise admixture. Our findings demonstrate that both metrics
can be effectively estimated using a simplified model of
nonlocality based solely on the violation of a specific class of
Bell inequalities.
The simplicity of these inequalities, expressed in terms of
correlation coefficients, renders them invaluable for practical
experimental investigations encompassing the themes discussed in
this paper. Notably, the nonlocal fraction derived from these
inequalities serves as a robust witness of genuine multipartite
entanglement, eliminating the need for distant parties to share a
common reference frame.
Speaker: Prof. Andrzej Grudka
Title: Superluminal observers and quantum superpositions
Affiliation: Nonlinear Optics Division, Institute of Spintronics
and Quantum Information, Faculty of Physics, Adam Mickiewicz
University, Poznań, Poland
Abstract: Recently Dragan and Ekert proposed that superluminal
observers can explain quantum superpositions. We construct system
of emitters and detectors and analyse their proposal in two
reference frames - one of usual subluminal observers ant the other
one of superluminal observers. We show that what they claim to be
superposition of two single photon paths from the point of view of
superluminal observers are in fact two paths of two photons.
Speaker: Prof. Paweł Kurzyński
Title: Non-classicality Primitive in a Quasi-probabilistic Toy
Model
Affiliation: Nonlinear Optics Division, Institute of Spintronics
and Quantum Information, Faculty of Physics, Adam Mickiewicz
University, Poznań, Poland
Abstract: We demonstrate a basic non-classical effect in a
quasi-probabilistic toy model with local Alice and Bob who share
classical randomness. Our scenario differs from the orthodox
demonstrations of non-classicality such as violations of Bell
inequalities where both local observers have a free will and
randomly choose their measurement settings. The core of the
argument are modified algorithms by Abramsky and Brandenburger [in
Horizons of the Mind, Springer, Cham (2014)], and Pashayan et. al.
[Phys. Rev. Lett. 115, 070501 (2015)] we use to show that if Bob
deterministically performs a quasi-stochastic operation, Alice and
Bob require classical communication to simulate it.
Speaker: Prof. Anna Kowalewska-Kudłaszyk
Title: On some examples of blocking photons and phonons
Affiliation: Nonlinear Optics Division, Institute of Spintronics
and Quantum Information, Faculty of Physics, Adam Mickiewicz
University, Poznań, Poland
Abstract: Photon blockades are the bosonic analogues of well known
Coulomb blockades for electrons. Systems in which photon blockades
appear may be used for example as perfect single (or two) photon
sources due to the fact that generation of one (or two) photons
blocks generation of more photons in the same system. For
successful blockades a presence of nonlinearity is necessary.
We will show that one of the possible sources of nonlinearity may
come from the interaction with squeezed reservoir [1].
Nonlinearity is also responsible for generation blockades and
other effect related to quantum correlations in hybrid modes of
optomechanical system [2]. Possible improvement of two-photon
blockade via quantum interference within a cavity with many
emitters will also be mentioned.
[1] A. Kowalewska-Kudłaszyk, S.I. Abo, G. Chimczak, J. Perina
Jr., F. Nori, A. Miranowicz Phys. Rev. A 100, 053857 (2019).
[2] S.I. Abo, G. Chimczak, A. Kowalewska-Kudłaszyk, J. Perina
Jr., R. Chhajlany and A. Miranowicz, Sc.Rep. 12, 17655 (2022).
Speaker: Prof. Ireneusz Weymann
Title: Kondo cloud in superconductors
Affiliation: Department of Mesoscopic Physics, Institute of
Spintronics and Quantum Information, Faculty of Physics, Adam
Mickiewicz University, Poznań, Poland
Abstract: (...)
Speaker: Prof. Ravindra Chhajlany
Title: Artificial quantum matter under control: from excitons to
atoms
Affiliation: Nonlinear Optics Division, Institute of Spintronics
and Quantum Information, Faculty of Physics, Adam Mickiewicz
University, Poznań, Poland
Abstract: (...)
Speaker: Prof. Karol Bartkiewicz
Title: Experimental exploration of Liouvillian exceptional points
on a quantum computer
Affiliation: Nonlinear Optics Division, Institute of Spintronics
and Quantum Information, Faculty of Physics, Adam Mickiewicz
University, Poznań, Poland
Abstract: (...)
Speaker: Dr. Kacper Wrześniewski
Title: Dynamics and cross-correlations in quantum dot-Majorana
wire systems
Affiliation: Department of Mesoscopic Physics, Institute of
Spintronics and Quantum Information, Faculty of Physics, Adam
Mickiewicz University, Poznań, Poland
Abstract: We theoretically investigate quench dynamics in quantum
dot system coupled to topological superconducting nanowire hosting
Majorana bound states. For the single quantum dot system, we
predict non-trivial competition between Majorana physics and
ferromagnetic correlations. High tunability of the system gives
precise control of discussed effects and opens many possibilities
for novel applications in spintronic quantum devices. Furthermore,
we analyze spin-polarized currents and associated
cross-correlations, and show that ferromagnetic contacts can
indicate imprints of Majorana physics. When another quantum dot is
attached to opposite edge of the nanowire, a non-local nature of
Majorana bound states is uncovered, evident in both dynamical
effects and in transport spectroscopy.
Speaker: Dr. Javid Naikoo
Title: Enhancing quantum sensors by capitalising on dynamical
instabilities
Affiliation: Nonlinear Optics Division, Institute of Spintronics
and Quantum Information, Faculty of Physics, Adam Mickiewicz
University, Poznań, Poland
Abstract: In my presentation, based on Phys. Rev. Lett. 131,
220801 (2023), I will delve into the cutting-edge realm of quantum
sensing, focusing on the utilization of dynamical singularities to
achieve unbounded sensitivity in the estimation of unknown
parameters. By integrating the multiparameter estimation theory of
Gaussian quantum systems with the study of singular-matrix
perturbations, I will discuss a novel framework for analyzing the
ultimate limits of precision attainable by singularity-tuned
sensors. This will allow us to identify the conditions under which
sensitivity diverges and at what rate, shedding light on the
fundamental capabilities of these quantum sensors. Moreover, I
will highlight the significance of accounting for nuisance
parameters in the analysis, as their presence may significantly
impact the scaling of error with the estimated parameter.
Speaker: Dr. Arnab Laha
Title: Speciality optical waveguide systems exhibiting conjugate
exceptional points
Affiliation: Nonlinear Optics Division, Institute of Spintronics
and Quantum Information, Faculty of Physics, Adam Mickiewicz
University, Poznań, Poland
Abstract: The occurrence of Exceptional Points (EP) is one of the
distinctive features of open (non-Hermitian) systems [1, 2]. The
understanding of the level-repulsion phenomenon within such a
system is associated with the occurrence of an EP and its
time-reversal (T) conjugate pair (say, EP*) in the underlying
parameter space [3, 4]. Here, we exploit the concept of conjugate
EPs in reporting a time (T)-symmetric correlation in all-optical
nonreciprocal light transmission [4]. Without any magneto-optical
effect, nonreciprocity is achieved based on a controlled Kerr-type
local nonlinearity in a planar gain-loss assisted waveguide.
Especially, we reveal a correlation between two T-symmetric
variants of the designed nonlinear waveguide, where dynamic
gain-loss variations around two conjugate EPs (in their respective
parameter spaces) allow asymmetric transfer of two different modes
through two waveguide variants, while considering the light
propagation in the same direction [4]. Here, both waveguide
variants block light in the reverse directions. The physical
aspects behind engineering conjugate EPs in such nonlinear optical
systems would enrich the platform for building nonreciprocal
components like isolators and circulators for all-photonic
circuits.
[1] Ş K. Özdemir, S. Rotter, F. Nori, and L. Yang, Nat. Mater. 18,
783 (2019)
[2] M.-A. Miri and A. Alu, Science 363, eaar7709
(2019)
[3] A. Laha, S. Dey, and S. Ghosh, Phys. Rev. A 105,
022203 (2022)
[4] A. Laha, A. Miranowicz, R. K. Varshney, and
S. Ghosh, Phys. Rev. A 109, 033511 (2024)
Speaker: Dr. Grzegorz Chimczak
Title: Good two-photon blockade displayed in the presence of a
cloud of emitters
Affiliation: Nonlinear Optics Division, Institute of Spintronics
and Quantum Information, Faculty of Physics, Adam Mickiewicz
University, Poznań, Poland
Abstract: We show that it is possible to observe an almost perfect
two-photon blockade in a quantum system consisting of an optical
cavity, a single atom, and a cloud of two-level emitters. This
result might seem surprising because, according to the
Holstein-Primakoff transformation, a big number of emitters
trapped inside the cavity should behave like quantum harmonic
oscillator, which is a linear system, while nonlinearity is
essential to observe any photon blockade phenomenon. We explain
this behavior by showing that the third-order correlation function
can have a negligibly small value in this system because of the
destructive interference phenomenon. The presented scheme exhibits
this almost perfect two-photon blockade for experimentally
feasible parameters.
Speaker: Dr. Marcin Karczewski
Title: Heralded entanglement generation with indistinguishable
particles
Affiliation: Nonlinear Optics Division, Institute of Spintronics
and Quantum Information, Faculty of Physics, Adam Mickiewicz
University, Poznań, Poland
Abstract: I am going to present my recent results concerning
heralded entanglement generation with identical particles. The
basic problem can be stated like this: consider a multiport given
by a unitary U. We cast N identical photons into its input modes
and measure the resulting photon numbers in some of its output
modes. How to design this process in such a way that a specific
pattern of registered photons will herald a target entangled state
in the modes with no detectors?
Speaker: M.Sc. Kuan-Yi Lee
Title: Unveiling quantum steering by quantum-classical uncertainty
complementarity
Affiliation: Center for Quantum Frontiers of Research and
Technology (QFort), National Cheng Kung University, Tainan 701,
Taiwan
Abstract: One of the remarkable aspects of quantum steering is its
ability to violate local uncertainty complementarity relations. In
this vein of study, various steering witnesses employing different
uncertainty relations have been developed including the famous
Reid's criteria. Here, we introduce a novel complementarity
relation between a system's quantum and classical uncertainties
corresponding to the distillable coherence and von-Neumann
entropy, respectively. We demonstrate its superior steering
detection efficiency compared to the entropic uncertainty
relation. Notably, our proposed steering witness can
Speaker: M.Sc. Yi-Te Huang
Title: An efficient Julia framework for hierarchical equations of
motion in open quantum systems
Affiliation:
1Department of Physics, National Cheng Kung
University, 701 Tainan, Taiwan.
2Center for Quantum Frontiers
of Research and Technology, NCKU, 701 Tainan, Taiwan.
Abstract: The hierarchical equations of motion (HEOM) approach can
describe the reduced dynamics of a system simultaneously coupled
to multiple bosonic and fermionic environments. The complexity of
exactly describing the system-environment interaction with the
HEOM method usually results in time-consuming calculations and a
large memory cost. Here, we introduce an open-source software
package called HierarchicalEOM.jl: a Julia framework integrating
the HEOM approach. HierarchicalEOM.jl features a collection of
methods to compute bosonic and fermionic spectra, stationary
states, and the full dynamics in the extended space of all
auxiliary density operators (ADOs). The required handling of the
ADOs multi-indexes is achieved through a user-friendly interface.
Speaker: M.Sc. Patrycja Tulewicz
Title: Advancing Generative Machine Learning with Quantum Computing
Authors: Patrycja Tulewicz1, Karol Bartkiewicz1, Jan Roik2, Karel Lemr2
Affiliations:
1Nonlinear Optics Division, Institute of Spintronics and
Quantum Information, Faculty of Physics, Adam Mickiewicz
University,
Poznań, Poland
2RCPTM, Joint Laboratory of Optics of Palacký University and
Institute of Physics of Czech Academy of Sciences, Olomouc, Czech
Republic
Abstract: [PDF]
The main difference between classical programming and machine learning (ML) is the reliance on explicit
instructions for the former, as opposed to ML. The implicit operation of ML can be particularly useful
for complex problems resistant to conventional methods, such as those in quantum systems. The integration
of quantum computing and machine learning appears to offer a promising solution to these challenges, with
additional benefits for the advancement of quantum information research. This talk will discuss how a new
approach to generative machine learning emerges from quantum state discrimination [1].
A novel approach, the Synergic Generative Adversarial Network (SGAN), significantly reduces the number
of hyperparameters required for generative quantum machine learning. This method supports collaboration
between generators and discriminator, outperforming traditional quantum generative adversarial learning
in some scenarios. Experimental results, both from quantum simulators and real quantum computers of
IBMQ [2], show the effectiveness of our approach. A system trained with our algorithm successfully learns
to recognize and generate maximally entangled states.
[1] Karol Bartkiewicz, Patrycja Tulewicz, Jan Roik, and Karel Lemr. Synergic quantum generative machine learning.
Scientific Reports, 13(1):12893, Aug 2023.
[2] IBM Quantum. https://quantum-computing.ibm.com/. 2021.
Speaker: M.Sc. Shilan Abo
Title: Pure dephasing of light-matter systems in the ultrastrong
and deep-strong coupling regimes
Affiliation: Nonlinear Optics Division, Institute of Spintronics
and Quantum Information, Faculty of Physics, Adam Mickiewicz
University, Poznań, Poland
Abstract: The field of cavity quantum electrodynamics holds great
promise for studying strong inter- actions between light and
matter. However, there is still a lot to be understood about pure
dephasing in quantum systems, especially in the strong coupling
regimes where new physical phenomena and quantum applications can
arise. In weak interaction scenarios, the difference in
perturbation forms between the dipole gauge and the Coulomb gauge
is often negligible. However, ignoring this difference can result
in incorrect and unphysical outcomes in ultra-strong and
deep-strong coupling regimes. In this talk I will address this
issue, focusing on calculating the pure dephasing rate in two
different models: the quantum Rabi model and the Hopfield model. I
will explain that the interaction in a light-matter system in
ultra- strong and deep-strong coupling regimes can significantly
impact the form of the stochastic perturbation that describes the
dephasing of a subsystem, depending on the gauge that is adopted
[1].
[1] A. Mercurio, S. Abo, F. Mauceri, E. Russo, V. Macri, A.
Miranowicz, S. Savasta, and O. Di Stefano, Pure Dephasing of
Light-Matter Systems in the Ultrastrong and Deep-Strong Coupling
Regimes, Phys. Rev. Lett. 130, 123601 (2023).
Speaker: B.Sc. Jędrzej Stempin
Title: Exploring position-dependent quantum random walks
Affiliation: Nonlinear Optics Division, Institute of Spintronics
and Quantum Information, Faculty of Physics, Adam Mickiewicz
University, Poznań, Poland
Abstract: Quantum Random Walks serve as simplified models for
understanding complex physical systems, such as solutions of the
Dirac equation. Drawing parallels with Classical Random Walks,
commonly used in search algorithms, highlights their potential
applications. Notably, Quantum Random Walks demonstrate superior
propagation speed compared to classical counterparts. Moreover,
incorporating position-dependent parameters leads to a faster wave
function spread. To get a deeper insight into the problem, we
explore the symmetries acquired by the evolution operator to
analyze Quantum Random Walks with position-dependent parameters.
Our investigation also includes discrete Wigner functions and
decoherence mechanisms, revealing the relationship between Quantum
and Classical Random Walks.
Speaker: B.Sc. Jan Wójcik
Title: Electrically coupled optomechanical cavities as a tool for
quantum nondemolition measurement
Affiliation: Nonlinear Optics Division, Institute of Spintronics
and Quantum Information, Faculty of Physics, Adam Mickiewicz
University, Poznań, Poland
Abstract: We present a new model of two electrically coupled
optomechanical cavities. We will show that coupling two
optomechanical cavities via Coulomb force leads to cross-Kerr
interactions between those cavities. We will further more prove
that such systems are perfect for a protocol of quantum
non-demolition measurement because the elimination of the
self-phase modulation effect is extremely simple. Moreover,
nonlinearities in our model are based on easily adjustable
parameters, and therefore, given recent experimental studies, we
believe that experimental realization of a cross-Kerr interaction
via Coulomb force coupling is feasible.
Satellite Talks
Date: Thursday 2024.05.09 at 15:00
Venue: Prof. S. Kielich's Auditorium
Satellite Talk in the series of the ISIK Seminars
Speaker: Prof. Franco Nori (keynote speaker)
Title: Quantum Optics with Giant Atoms: Decoherence-Free
Interaction between Giant Atoms in Waveguide Quantum
Electrodynamics
Affiliations:
1Theoretical Quantum Physics Laboratory, Center for Quantum
Computing, RIKEN, Japan
2Physics Department, The University of Michigan, Ann Arbor, USA
Abstract: [PDF] In quantum optics, atoms are usually
approximated as point-like compared to the wavelength of the light
they interact with. However, recent advances in experiments with
artificial atoms built from superconducting circuits have shown
that this assumption can be violated. Instead, these artificial
atoms can couple to an electromagnetic field in a waveguide at
multiple points, which are spaced wavelength distances apart. Such
systems are called giant atoms. They have attracted increasing
interest in the past few years (e.g., see the review in [1]), in
particular because it turns out that the interference effects due
to the multiple coupling points allow giant atoms to interact with
each other through the waveguide without losing energy into the
waveguide (theory in [2] and experiments in [3]).
This talk will review some of these developments [1-4]. Finally, we will also show how a giant atom coupled to a waveguide with varying impedance can give rise to chiral bound states [5].
[1] A.F. Kockum, Quantum optics with giant atoms - the first five years, arxiv:1912.13012
[2] A.F. Kockum, G. Johansson, F. Nori, Decoherence-Free Interaction between Giant Atoms in Waveguide Quantum Electrodynamics, Phys. Rev. Lett. 120, 140404 (2018).
[3] B. Kannan, et al., Waveguide quantum electrodynamics with superconducting artificial giant atoms, Nature 583, pp. 775 (2020).
[4] S. Terradas-Brianso, et al., Ultrastrong waveguide QED with giant atoms, Phys. Rev. A 106, 063717 (2022).
[5] X. Wang, T. Liu, A.F. Kockum, H.R. Li, F. Nori, Tunable Chiral
Bound States with Giant Atoms, Phys. Rev. Lett. 126, 043602
(2021).
Chair: Prof. Ireneusz Weymann
Date: Monday 2024.05.13 at 16:00
Venue: Auditorium Maximum
Speaker: Prof. Franco Nori (keynote speaker)
Satellite Talk in the series of Stanislaw Ulam's Lectures
Title: Artificial neural networks and Machine Learning applied to
Quantum Physics
Affiliations:
1Theoretical Quantum Physics Laboratory, Center for Quantum
Computing, RIKEN, Japan
2Physics Department, The University of Michigan, Ann Arbor, USA
Abstract: This talk is geared to an audience of mostly physicists,
mathematicians, and computer scientists. It turns out that, over
70 years ago, a physicist (Fermi), a mathematician (Ulam), and a
computer scientist (Pasta) worked together in a very important
problem, that had a huge impact in the development of nonlinear
dynamics, chaos, solitons, and studies of thermalization in
statistical mechanics. Thus, I would like to briefly summarize the
initial history of this very interesting problem, involving
Stanislav Ulam and his collaborators.
The Fermi-Pasta-Ulam problem initially posed a paradox but
ultimately led to a significant discovery. Enrico Fermi, John
Pasta, and Stanislav Ulam introduced it in the early 1950s to
explore fundamental principles of equilibrium statistical
mechanics, such as energy equipartition and ergodicity. Employing
the MANIAC-I computer at Los Alamos, they numerically integrated
equations of motion for a carefully selected one-dimensional
harmonic chain of mass points subject to weak nonlinear forces.
Their expectation was that the system would converge towards
equilibrium, with energy evenly distributed across all degrees of
freedom. However, contrary to their anticipation, the system
displayed nearly periodic behavior. This apparent contradiction
was later elucidated by the revelation of solitons—localized waves
that maintain their shape as they propagate. Consequently, the
Fermi-Pasta-Ulam problem has evolved into a pivotal aspect of
modern nonlinear mechanics and has undergone extensive scrutiny
and analysis for the past 70 years.
The solution to the puzzle they were studying involved the use of
computers, at that time relatively new. This is because complex
problems require the use of powerful computational tools. Most of
this talk will be devoted to presenting (far more recent and far
more powerful) computational techniques in artificial intelligence
(AI), which are impacting all aspects of science, engineering, and
society in general. The talk will present some basic aspects of
simple artificial neural networks and machine learning (ML), and
how these can be applied to the study of several problems in
quantum physics and quantum information science. Entire flagship
research programs are being devoted all over the world to study
these two areas of research (AI and quantum information), and we
will very briefly overview some aspects of both.
Chair: Prof. Michał Banaszak
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