Virtual Poster Session for POSTER SESSION QTD 2020

POSTER SESSION QTD 2020

ICFO


Welcome to the Poster Session!


Wednesday 21st 12:00-16:00 (CEST) the poster presenters will be online and available to have chat with you. 


Leave your questions and comments or start a conversation in the Poster Session Blog Roll.


QTD 2020 is the annual conference on quantum thermodynamics. 

The main goal of the conference is to discuss the recent advances on quantum thermodynamics, the field that studies thermodynamic processes at the quantum scale. 


More info: http://qtd2020.icfo.eu/

Filter displayed posters (37 tags)

#ThermalOperations (2) quantum (2) show more... #Catalysis (1) #GKSL (1) #IrreversibleEngines (1) #NESS (1) #Nonlocalthermoelectricity (1) #QuantumHeatEngines (1) #QuantumThermo (1) #QuantumThermodynamics (1) #ResourceTheories (1) #StepEngines (1) #TopologicalJosephsonJunctions (1) #TranslationalInvariance (1) #adiabaticity (1) #causality (1) #decoherence (1) #decoherence-free-subspaces (1) #entropy-production (1) #many-body-systems (1) #monitoratingenergy (1) #non-Markovianity (1) #nonmarkovianity (1) #qtd2020 (1) #quantumcontrol (1) #quantumheatmachines (1) #quantumopensystemdynamics (1) #quantumswitch (1) #quantumthermodynamics, (1) #resourcetheories (1) #resourcetheories, (1) #thermalchannels (1) correlations, (1) efficiency (1) engine, (1) increase (1) thermal (1)
Show Posters:

All states are universal catalysts in quantum thermodynamics

Patryk Lipka-Bartosik, Paul Skrzypczyk

Abstract
Quantum catalysis is a fascinating concept which demonstrates that certain transformations can only become possible when given access to a specific resource that has to be returned unaffected. It was first discovered in the context of entanglement theory and since then applied in a number of resource-theoretic frameworks, including quantum thermodynamics. Although in that case the necessary (and sometimes also sufficient) conditions on the existence of a catalyst are known, almost nothing is known about the precise form of the catalyst state required by the transformation. In particular, it is not clear whether it has to have some special properties or be finely tuned to the desired transformation. In this work we describe a surprising property of multi-copy states: we show that in resource theories governed by majorization all resourceful states are catalysts for all allowed transformations. In quantum thermodynamics this means that the so-called "second laws of thermodynamics" do not require a fine-tuned catalyst but rather any state, given sufficiently many copies, can serve as a useful catalyst. JOIN IN TO HAVE A CHAT! Passcode: catalysis
Presented by
Patryk Lipka-Bartosik
Institution
University of Bristol
Hashtags
#QuantumThermodynamics #ThermalOperations #Catalysis #ResourceTheories
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Available 12:30 am - 4 pm CEST

Andreev-Coulomb drag in coupled quantum dot systems

S. Mojtaba Tabatabaei, David Sánchez, Alfredo Levy Yeyati, Rafael Sánchez

Abstract
Electrical power can be generated in a quantum dot system that rectifies the energy absorbed from non-equilibrium fluctuations of its environment. Typically, this depends on tiny energy-dependent asymmetries of the device [1]. We show that larger currents are expected in hybrid systems, where a superconductor hybridizes even-parity states (with 0 and 2 electrons) in the quantum dot. We consider the environment to consist on a quantum dot Coulomb-coupled to the conductor one. The non-equilibrium charge fluctuations in the second dot correlate with the Andreev processes that inject Cooper pairs in the superconductor. This provides the necessary symmetry breaking energy transfer. We analyze this mechanism in two configurations depending on the non-equilibrium source: i.e., when the quantum dot is coupled to (i) two terminals at different chemical potential, and (ii) a single but hot terminal. We show that pair and quasiparticle contributions can be distinguished by a change of sign of the generated current. The investigation of the injected heat current provides additional insights and enable the definition of gate-tunable heat engines based on quantum many-body correlations.

[1] H. Thierschmann et al., Nat. Nanotechnol. 10, 854 (2015). [2] S.M. Tabatabaei et al, arXiv:2009.12398
Presented by
Rafael Sanchez
Institution
Universidad Autónoma de Madrid
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Available October 21st, 12:00-15:00

Approximation of non-Markovian dynamics by Markovian one in all orders of perturbation theory

Alexander Teretenkov

Abstract
We study the perturbative corrections to the weak-coupling-limit-type Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) equation for the reduced density matrix of an open system. We show that the expansion of the density matrix in powers of the small parameter has a different initial condition than the whole density matrix. On the well known example of the spin-boson model in the rotating wave approximation at zero temperature we show that the perturbative part of the density matrix satisfies the time-independent GKSL equation for arbitrary order of the perturbation theory if all the moments of correlation function exist. The naive usage of the whole density matrix initial condition without the correction we propose would lead to the mistake in this case.
Presented by
Alexander Teretenkov <taemsu@mail.ru>
Institution
Steklov Mathematical Institute of Russian Academy of Sciences. Department of Mathematical Methods for Quantum Technologies
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Attaining Carnot Efficiency with Quantum and Nano-scale Heat Engines

Mohit Lal Bera1, Maciej Lewenstein 1,2 and Manabendra Nath Bera 3

Abstract
A heat engine that operates in the one-shot finite-size regime, where systems composed of a small number of quantum particles interact with hot and cold baths and are restricted to one-shot measurements, delivers fluctuating work. Further, engines with lesser fluctuation produce lesser amount of deterministic work. Hence, the heat-to-work conversion efficiency stays well below the Carnot efficiency. Here we overcome this limitation and attain Carnot efficiency in the one-shot finite-size regime, where the engines allow the working systems to simultaneously interact with two baths via the semi-local thermal operations and reversibly operate in a one-step cycle. These engines are superior to the ones considered earlier in work extraction efficiency, and, even, are capable of converting heat into work by exclusively utilizing inter-system correlations. We formulated a resource theory for quantum heat engines to prove the results.
Presented by
Mohit Lal Bera
Institution
1) ICFO – Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, ES-08860 Castelldefels, Spain 2) ICREA, Pg. Lluis Companys 23, ES-08010 Barcelona, Spain 3) Department of Physical Sciences, Indian Institute of Science Education and Research (IISER), Mohali, Punjab 140306, India
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Beyond local and global approaches for localized dissipation

D. Farina, G. De Filippis, V. Cataudella, M. Polini and V. Giovannetti

Abstract
Identifying which master equation is preferable for the description of a multipartite open quantum system is not trivial and has led in the recent years to the local vs global debate in the context of Markovian dissipation. We treat here a paradigmatic scenario in which the system is composed of two interacting harmonic oscillators A and B, with only A interacting with a thermal bath - collection of other harmonic oscillators. We show that the completely positive (CP) version of the Redfield equation obtained using coarse-grain and an appropriate time-dependent convex mixture of the local and global solutions give rise to the most accurate CP approximations of the whole exact system dynamics, i.e. both at short and at long time scales, outperforming the local and global approaches.

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Presented by
Donato Farina <donato.farina@sns.it>
Institution
Scuola Normale Superiore of Pisa
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Charging, energy fluctuations and dissipation of a two-level quantum battery

Alba Crescente

Abstract
We consider a two-level quantum system driven by an external classical source as the simplest possible building block of a quantum battery (QB). Here we analyze the performance of this device in terms of energy storage, time of charging and energy fluctuations during the charging process. Using a numerical analysis, we characterize the role of different initial conditions for the system as well as the sensitivity for the functional form of the drive. Moreover dissipation due to the presence of an environment is considered. In the weak-coupling regime analytical expressions of the stored energy are found. Here we analyze how the interaction with a thermal reservoir affects the dynamics of the quantum battery. This study aims at providing a solid theoretical background in view of future experimental implementations.
Presented by
Alba Crescente
Institution
Dipartimento di Fisica, Università di Genova; SPIN-CNR.
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Available April 21th 2020, 2-4pm EST

Collision models can efficiently simulate any multipartite Markovian dynamics

Marco Cattaneo, Gabriele De Chiara, Sabrina Maniscalco, Gian Luca Giorgi and Roberta Zambrini

Abstract
We introduce the Multipartite Collision Model (MCM) to simulate the Markovian dynamics of any multipartite open quantum system by decomposing the system-environment interaction into elementary collisions between subsystems and ancillae, thus providing a simple decomposition in terms of elementary quantum gates for quantum computation. The generality of the model allows for the study of any possible Markovian global and local master equation in the presence of any kind of bath at any temperature. Moreover, we develop a method to estimate an analytical error bound for any repeated interactions model, and we use it to show that the error of the Multipartite Collision Model displays an optimal behavior. Finally, we proof that the Multipartite Collision Model is efficiently simulable on a quantum computer according to the dissipative quantum Church-Turing theorem.
Presented by
Marco Cattaneo
Institution
IFISC (CSIC-UIB) and University of Turku
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Continuous Monitoring of Energy in Quantum Open Systems

Gabriel P. Martins, Nadja K. Bernardes, and Marcelo F. Santo

Abstract
We propose a method to continually monitor the energy of a quantum system. We show that by having some previous knowledge of the system's dynamics, but not all of it, one can use the measured energy to determine many other quantities, such as the work performed on the system, the heat exchanged between the system and a thermal reservoir, the time dependence of the Hamiltonian of the system as well as the total entropy produced by its dynamics. We have also analyzed how this method is dependent on the quality factor of the measurements employed.
Presented by
Nadja K. Bernardes
Institution
Universidade Federal de Minas Gerais; Universidade Federal de Pernambuco; Universidade Federal do Rio de Janeiro
Hashtags
#quantumopensystemdynamics #monitoratingenergy
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Available 14:00-16:00 (CET)

Counter-intuitive properties of a simple quantum heat engine

Thiago R. de Oliveira

Abstract
We present a simple quantum mechanism for efficiency increase in quantum thermal engines operating with a Otto cycle that do not involve any quantum correlation or coherence as previous studies. The mechanism is based on the structure of the energy spectrum; the fact that some of the levels do not couple to the external agent that realizes work. Besides an efficiency increase this mechanism also allow for many counter intuitive phenomenology when the bath temperatures change. For example, its thermodynamic efficiency may increase as their temperature difference decreases. Conversely, the engine may cease to operate if the hotter bath becomes too hot, or the colder bath too cold, even in the limit of absolute zero temperature. Moreover, in some circumstance, the engine may run in either sense of the same thermodynamic cycle, with the physical heat reservoirs exchanging the roles of ‘hot’ or ‘cold’ bath. Finally, all these phenomena can be understood using a simple physical picture in terms of energy flows via each system level.
Presented by
Thiago Rodrigues de Oliveira <troliveira@id.uff.br>
Institution
Universidade Federal Fluminense
Hashtags
quantum thermal engine, quantum correlations, efficiency increase
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Available Wed 21 Oct 12:00-16:00 CEST

Critical heat current for operating an entanglement engine

Shishir Khandelwal, Nicolas Palazzo, NIcolas Brunner, Géraldine Haack

Abstract
Autonomous entanglement engines have recently been proposed to generate steady-state bipartite and multipartite entanglement exploiting only incoherent interactions with thermal baths at different temperatures. In this work, we investigate the interplay between heat current and entanglement in a two-qubit entanglement engine, deriving a critical heat current for successful operation of the engine, i.e. a cut-off above which entanglement is present. The heat current can thus be seen as a witness to the presence of entanglement. In the regime of weak-inter qubit coupling, we also investigate the effect of two experimentally relevant parameters for the qubits, the energy detuning and tunnelling, on the entanglement production. Finally, we show that the regime of strong inter-qubit coupling provides no clear advantage over the weak regime, in the context of out-of-equilibrium entanglement engines. JOIN IN TO HAVE A CHAT! Meeting ID: 246 819 7746. Passcode: QTD
Presented by
Shishir Khandelwal
Institution
University of Geneva
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Density and state metrics to measure adiabaticity in quantum many-body systems at zero and finite temperature

Amy Skelt and Irene D’Amico

Abstract
Adiabatic evolutions of many-body quantum systems are very important in various fields of physics, from quantum computing to quantum thermodynamics to atomic and molecular physics, to name a few. However, current methods for characterizing adiabaticity, such as the quantum adiabatic criterion, are designed for pure states at zero temperature, while most applications are based on many-body systems at finite temperature, and so new insights and techniques are needed. We demonstrate that appropriate metrics for the system state and for its corresponding local particle-density can be used to quantitatively determine the degree of adiabaticity of the dynamics of quantum many-body systems, at zero [1] and finite [2] temperature. This is important for quantum technologies and quantum thermodynamics related protocols. We show that the Bures and the trace distance, both well defined at finite temperatures, are reliable measures of adiabaticity, both qualitatively and quantitatively. Importantly, and in addition, adiabaticity can be characterized using only the local particle density distance. The local particle density is a much more accessible quantity, both experimentally and computationally, especially when handling many-body systems. The importance of considering memory effects is discussed by comparing the metrics' results to the ones obtained by extending the quantum adiabatic criterion to finite temperatures [2]: the latter may produce false readings being quasi-Markovian by construction. The possibility of characterizing the degree of adiabatic evolution via the system local particle densities, makes this method potentially applicable to very large many-body systems and to experiments.

[1] A. H. Skelt, R. W. Godby, and I. D'Amico, Phys. Rev. A 98, 012104 (2018) [2] A. H. Skelt, and I. D'Amico, Adv. Quantum Technol. 3, 1900139 (2020)

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Presented by
Irene D'amico
Institution
Department of Physics, University of York, York, UK
Hashtags
#adiabaticity #many-body-systems
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Available 14:00 - 16:00 CEST

Engineering dissipation to control thermalization

Aurelia Chenu

Abstract
Control technics known as ’Shortcuts to Adiabaticity’ allow to reach a target final state in a definite time, and find application, e.g., in quantum thermodynamics to shorten the running time of a quantum thermal cycle. Such control was, until recently, restricted to unitary dynamics. We now extend their realm of application to open dynamics, where dissipation is engineered. The first application allows controlling thermalization [1]. Considering a particle in a driven harmonic trap, we provide the control parameters (trap frequency and dephasing strength) to transform an initial state into a final thermal state in a finite time. Experimental implementation in the laboratory relies on stochastic parametric driving, which is readily accessible in current platforms. A second application is shown to control, in addition of thermalization, squeezing [2]. The technique is detailed in the setting of trapped-ion experiments with two-photon Raman interaction, where the desired open dynamics is obtained from stochastically shaking the trapping potential. We provide solutions for the control parameters (laser amplitude, phase, and dephasing strength) that allow creating a squeezed thermal state at controlled temperature in arbitrary time.

References: [1] L. Dupays, I. L. Egusquiza, A. del Campo, and A. Chenu. Superadiabatic thermalization of a quantum oscillator by engineered dephasing , Phys. Rev. Res. 2:033178 (2020) [2] L. Dupays and A. Chenu. Dynamical engineering of squeezed thermal state, ArXiv2008.033027 (2020)
Presented by
Aurelia Chenu
Institution
DIPC
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Entropy Production, Decoherence, and Non-Equilibrium Steady States of the GKSL equation

Anton Trushechkin

Abstract
The poster is devoted to mathematical properties of the Gorini–Kossakowski–Sudarshan–Lindblad (GKSL) master equation related to entropy production, non-equilibrium steady states, decoherence and, on the contrary, conservation of coherences.

For the GKSL equation, we define the entropy production functional. The definition is motivated by the complementary quantum channel concept. Also we expand the total entropy production into the adaibatic and non-adiabatic contributions. We proof the non-negativity of the total, non-adiabatic and adiabatic entropy productions (the last one – only in the vicinity of a stationary state or everywhere, but with additional assumprions) based on purely operator theory and convex functions techniques.

Based on these results, we find a necessary and sufficient condition for a given quantum state to be a stationary solution of the GKSL equation, for a certain class of GKSL equation. An example of analytic calculation of the non-equilibrium steady state of two qubits interacting with each other as well as with two baths (a hot one and a cold one) and an example of analytic calculation of the full family of steady states for a system with coherence trapping will be presented.

Also we present necessary and sufficient conditions for decoherence or, on the contraty, conservation of coherences in solutions of the GKSL equation, which can be used in the development of quantum computers and quantum thermodynamic machines.
Presented by
Anton Trushechkin
Institution
Steklov Mathematical Institute of the Russian Academy of Sciences
Hashtags
#GKSL #entropy-production #NESS #decoherence #decoherence-free-subspaces
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Available October 21, 12:00-16:00 CEST

Ergotropy from indefinite causal orders

Kyrylo Simonov1, Gianluca Francica2, Giacomo Guarnieri3, Mauro Paternostro4

Abstract
We characterize the impact that the application of two consecutive quantum channels or their quantum superposition (thus, without a definite causal order) has on ergotropy, i.e. the maximum work that can be extracted from a system through a cyclic unitary transformation. We show that commutative channels always lead to a non-negative gain and perform a thorough analysis for qubit channels and provide general conditions for achieving a positive gain on the incoherent part of ergotropy.
Presented by
Kyrylo Simonov
Institution
(1)Fakultat fur Mathematik, Universitat Wien, Oskar-Morgenstern-Platz 1, 1090 Vienna, Austria (2)CNR-SPIN, I-84084 Fisciano (SA), Italy (3)School of Physics, Trinity College Dublin, Dublin 2, Ireland (4)Centre for Theoretical Atomic, Molecular and Optical Physics, Queen's University Belfast, Belfast BT7 1NN, United Kingdom
Hashtags
#causality #quantumcontrol #quantumswitch #thermalchannels #resourcetheories

Experimental measurement of entropy production for decorrelation processes

Patrice A. Camati, Guillaume Cauquil, Zheng Tan, Michel Brune, Jean-Michel Raimond, Alexia Auffèves, and Igor Dotsenko

Abstract
We employ the two-point measurement scheme to derive the (average) entropy production for two decorrelation processes. The full decorrelation process erases all correlations of a bipartite system while a local docherence process erases only the quantum correlations. We show that the mutual information and the relative entropy of coherence in a suitable basis quantify the entropic cost of erasing all correlations or only the quantum correlations, respectively. We propose a method to experimentally measure these quantities in a cavity QED setup.
Presented by
Patrice Camati <patrice.camati@neel.cnrs.fr>
Institution
Institut Néel - CNRS
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Available October 21th 12-16h CEST

Fast and accurate Cooper pair pump

P. A. Erdman, F. Taddei, J. T. Peltonen, R. Fazio, and J. P. Pekola

Abstract
We propose a method to perform accurate and fast charge pumping in superconducting nanocircuits. Combining topological properties and quantum control techniques based on shortcuts to adiabaticity, we show that it is theoretically possible to achieve perfectly quantised charge pumping at any finite-speed driving. Model-specific errors may still arise due the difficulty of implementing the exact control. We thus assess this and other practical issues in a specific system comprised of three Josephson junctions. Using realistic system parameters, we show that our scheme can improve the pumping accuracy of this device by various orders of magnitude. Possible metrological perspectives are discussed.
Presented by
Paolo Andrea Erdman
Institution
Scuola Normale Superiore, Pisa
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Local master equations bypass the secular approximation

Stefano Scali, Janet Anders and Luis A. Correa

Abstract
Master equations are a vital tool to model heat flow through nanoscale thermodynamic systems. Most practical devices are made up of interacting sub-system, and are often modelled using either local master equations (LMEs) or global master equations (GMEs). While the limiting cases in which either the LME or the GME breaks down are well understood, there exists a 'grey area' in which both equations capture steady-state heat currents reliably, but predict very different transient heat flows. In such cases, which one should we trust? Here, we show that, when it comes to dynamics, the local approach can be more reliable than the global one for weakly interacting open quantum systems. This is due to the fact that the secular approximation, which underpins the GME, can destroy key dynamical features. To illustrate this, we consider a minimal transport setup and show that its LME displays exceptional points (EPs). These singularities have been observed in a superconducting-circuit realisation of the model. However, in stark contrast to experimental evidence, no EPs appear within the global approach. We then show that the EPs are a feature built into the Redfield equation, which is more accurate than the LME and the GME. Finally, we show that the local approach emerges as the weak-interaction limit of the Redfield equation, and that it entirely avoids the secular approximation.

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Presented by
Luis A. Correa
Institution
University of Exeter / CEMPS — Physics and Astronomy
Hashtags
#qtd2020 #QuantumThermo
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Available October 21, 12:00–15:00 CEST

Nonlocal thermoelectricity in hybrid Topological Josephson junctions

Gianmichele Blasi, Fabio Taddei, Liliana Arrachea, Matteo Carrega, and Alessandro Braggio

Abstract
Here we investigate the thermoelectrical properties of an hybrid topological Josephson junction (TJJ) in contact with a normal-metal probe. Usually, finite thermoelectric response appears in hybrid superconducting systems only when the particle-hole symmetry is broken. However, by relying on a multiterminal configuration and nonlocal signals, novel mechanisms for topological insulators are opened. Indeed, when a temperature bias is applied to the superconducting terminals of the TJJ, a nonlocal thermoelectric current is established in the normal probe as a direct consequence of the helical nature of the edge states.

Here we present two works in which we discuss the emergence of such a nonlocal thermoelectric response (i) obtained through the application of an external magnetic flux inducing the so called Doppler shif effect or (ii) generated by a purely Andreev interferometric mechanism, which can be tuned by imposing a Josephson phase diffeerence between the two superconductors. We fully characterize thermoelectric linear response and performance of this hybrid junction in both cases, and provide also a realistic estimation of the nonlocal Seebeck coefficient.
Presented by
Gianmichele Blasi <gianmichele.blasi@sns.it>
Institution
Scuola Normale Superiore di Pisa
Hashtags
#Nonlocalthermoelectricity #TopologicalJosephsonJunctions

Performance of a quantum Otto refrigerator based on non-Markovian dynamics

Patrice A. Camati, Jonas F. G. Santos, and Roberto M. Serra

Abstract
The extension of quantum thermodynamics to situations that go beyond standard thermodynamic settings comprises an important and interesting aspect of its development. One such situation is the analysis of the thermodynamic consequences of structured environments that induce a non-Markovian dynamics. We study a quantum Otto refrigerator where the standard Markovian cold reservoir is replaced by a specific engineered cold reservoir which may induce a Markovian or non-Markovian dynamics on the quantum refrigerant system. The two dynamical regimes can be interchanged by varying the coupling between the refrigerant and the reservoir. An increase of non-Markovian effects will be related to an increase of the coupling strength, which in turn will make the energy stored in the interaction Hamiltonian, the interaction energy, increasingly relevant. We show how the figures of merit, the coefficient of performance, and the cooling power change for non-negligible interaction energies, discussing how neglecting this effect would lead to an overestimation of the refrigerator performance. Finally, we also consider a numerical simulation of a spin quantum refrigerator with experimentally feasible parameters to better illustrate the non-Markovian effects induced by the engineered cold reservoir. We argue that a moderate non-Markovian dynamics performs better than either a Markovian or a strong non-Markovian regime of operation.
Presented by
Jonas F. G. Santos <jonasfgs18@gmail.com>
Institution
Centro de Ciências Naturais e Humanas, Universidade Federal do ABC and Université Grenoble Alpes, Centre National de la Recherche Scientifique
Hashtags
#quantumthermodynamics, #nonmarkovianity #quantumheatmachines
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Available October 21st, 13h-16pm

Quantum Field Machines

João Sabino

Abstract
The field of quantum thermodynamics has evolved significantly over the past years, trying to make clear the role of quantum features in the properties of thermodynamic systems. However, the development of experiments implementing and testing the ideas of quantum thermodynamics, e.g. quantum thermal machines, is still in an early stage. In this work, we propose an experimental implementation of a quantum thermodynamic cycle using 1D clouds of ultra-cold atoms trapped with an atomchip. Using this experimental framework, together with a Digital Micro-Mirror-Device, we are able to design traps and potentials which allow us to implement and study the primitive operations needed for a quantum version of a thermal machine.
Presented by
João Sabino <joao.sabino@tuwien.ac.at>
Institution
TU WIen and Instituto Superior Técnico
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Available 21 October - 1pm-4pm

Quantum master equation for continuous feedback control

Björn Annby-Andersson, Peter Samuelsson, Patrick Potts

Abstract
Abstract: Feedback-controlled systems have recently become a hot topic due to the experimental ability of realizing Maxwell's demon [1-3]. Previous theories on feedback in quantum systems, mainly developed in the framework of quantum optics, usually rely on homodyne detection [4,5]. In this work, we develop a general theoretical model describing feedback-controlled systems continuously monitored by a detector with finite bandwidth. Our main result is a Fokker-Planck-like master equation defining how the system state and measurement outcome evolve in time.

[1] J . V. Koski et al., Proc. Natl. Acad. Sci. U.S.A. 111, 13786 (2014) [2] M. Naghiloo et al, Phys. Rev. Lett. 121, 030604 (2018) [3] Y. Masuyama et al., Nat. Commun. 9, 1291 (2018) [4] H. M. Wiseman et al., Phys. Rev. Lett. 70, 548 (1993) [5] H. M. Wiseman, Phys. Rev. A 49, 2133 (1994) [6] A. Bednorz et al., New J. Phys. 14, 013009 (2012) [7] B. Annby-Andersson et al., Phys. Rev. B 101, 165404 (2020)
Presented by
Björn Annby-Andersson
Institution
Lund University
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Available Oct 21 12-16h

Quantum state engineering by shortcuts-to-adiabaticity

O. Abah, R. Puebla and M. Paternostro

Abstract
We present a fast and robust framework to prepare non-classical states of a bosonic mode exploiting a coherent exchange of excitations with a two-level system ruled by a Jaynes-Cummings interaction mechanism. Our protocol, which is built on shortcuts to adiabaticity, allows for the generation of arbitrary Fock states of the bosonic mode, as well as coherent quantum superpositions of a Schr\"odinger cat-like form. In addition, we show how to obtain a class of photon-shifted states where the vacuum population is removed, a result akin to photon addition, but displaying more non-classicality than standard photon-added states. Owing to the ubiquity of the spin-boson interaction that we consider, our proposal is amenable for implementations in state-of-the-art experiments.
Presented by
Obinna Abah
Institution
Queen's University Belfast, United Kingdom
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Quantum systems correlated with a finite bath: nonequilibrium dynamics and thermodynamics

Andreu Riera-Campeny, Anna Sanpera and Philipp Strasberg

Abstract
Describing open quantum systems far from equilibrium is challenging, in particular when the environment is mesoscopic, when it develops nonequilibrium features during the evolution, or when memory effects cannot be disregarded. Here, we derive a master equation that explicitly accounts for system-bath correlations and includes, at a coarse-grained level, a dynamically evolving bath. It applies to a wide variety of environments, for instance, those which can be described by Random Matrix Theory or the Eigenstate Thermalization Hypothesis. We obtain a local detailed balance condition which, interestingly, does not forbid the emergence of stable negative temperature states in unison with the definition of temperature through the Boltzmann entropy. We benchmark the master equation against the exact evolution and observe a very good agreement in a situation where the conventional Born-Markov-secular master equation breaks down. Interestingly, the present description of the dynamics is robust and it remains accurate even if some of the assumptions are relaxed. Even though our master equation describes a dynamically evolving bath not described by a Gibbs state, we provide a consistent nonequilibrium thermodynamic framework and derive the first and second law as well as the Clausius inequality. Our work paves the way for studying a variety of nanoscale quantum technologies including engines, refrigerators, or heat pumps beyond the conventionally employed assumption of a static thermal bath. JOIN IN TO HAVE A CHAT! Meeting ID: 984 1581 7250. Passcode: 5LadXt
Presented by
Andreu Riera-Campeny <andreu.riera.campeny@uab.cat>
Institution
Universitat Autònoma de Barcelona, Departament de Física: Informació i Fenòmens Quàntics
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Available 12.00h a 14.00h CEST

Quantum work statistics with initial coherence

María García Díaz, Giacomo Guarnieri, Mauro Paternostro

Abstract
The Two Point Measurement scheme for computing the thermodynamic work performed on a system requires it to be initially in equilibrium. The Margenau-Hill scheme, among others, extends the previous approach to allow for a non-equilibrium initial state. We establish a quantitative comparison between both schemes in terms of the amount of coherence present in the initial state of the system, as quantified by the l1-coherence measure. We show that the difference between the two first moments of work, the variances of work and the average entropy production obtained in both schemes can be cast in terms of such initial coherence. Moreover, we prove that the average entropy production can take negative values in the Margenau-Hill framework.

Ref: Quantum work statistics with initial coherence. https://arxiv.org/abs/2007.00042
Presented by
María García Díaz
Institution
Universitat Autònoma de Barcelona
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Available Wed 21 Oct 12:00-16:00 CEST

Resouce Preservability and Thermodynamics

Chung-Yun Hsieh

Abstract
Resource theory is a general, model-independent approach aiming to understand the qualitative notion of resource quantitatively. In a given resource theory, free operations are physical processes that do not create resource and are considered zero-cost. This brings the following natural question: For a given free operation, what is its ability to preserve a resource? We axiomatically formulate this ability as the resource preservability, which is constructed as a channel resource theory induced by a state resource theory. Using distance measure, we provide a general class of resource preservability monotones. Specifically, this gives the robustness monotone, which is related to the bath sizes for thermalization when we consider the preservation of athermality as the resource. As an application, unexpectedly, we found that the smallest bath size needed to thermalize all outputs of a Gibbs-preserving coherence-annihilating channel upper bounds its non-signaling assisted one-shot classical capacity. In this sense, bath sizes can be interpreted as the thermodynamic cost of transmitting classical information. Our results give the first systematic and general formulation of the resource preservation of free operations.
Presented by
Chung-Yun Hsieh
Institution
ICFO
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Available 13:00 - 15:00 CEST

Resource theories of multi-time processes: A window into non-Markovianity

Graeme D. Berk, Andrew J. P. Garner, Benjamin Yadin, Kavan Modi, Felix A. Pollock

Abstract
We investigate the conditions under which an uncontrollable background processes may be harnessed by an agent to perform a task that would otherwise be impossible within their operational framework. This situation can be understood from the perspective of resource theory: rather than harnessing 'useful' quantum states to perform tasks, we propose a resource theory of quantum processes across multiple points in time. Uncontrollable background processes fulfil the role of resources, and a new set of objects called superprocesses, corresponding to operationally implementable control of the system undergoing the process, constitute the transformations between them. After formally introducing a framework for deriving resource theories of multi-time processes, we present a hierarchy of examples induced by restricting quantum or classical communication within the superprocess - corresponding to a client-server scenario. The resulting nine resource theories have different notions of quantum or classical memory as the determinant of their utility. Furthermore, one of these theories has a strict correspondence between non-useful processes and those that are Markovian and, therefore, could be said to be a true 'quantum resource theory of non-Markovianity'.
Presented by
Graeme Berk
Institution
Monash University
Hashtags
#resourcetheories, #non-Markovianity
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Available 12-14 CEST, 21/10/20

The relation between two different ways of calculating transport coefficients

Archak Purkayastha

Abstract
Linear response transport coefficients of a system are important quantities for quantum thermodynamics. For example, the performance of an autonomous quantum heat engine can be characterized in terms of the elements of the Onsager matrix, which are the transport coefficients of the working medium. There are two standard ways of calculating transport coefficients of a system. In the first way, one considers an isolated system in the thermodynamic limit, and applies Green- Kubo formula. The transport coefficients are then obtained in terms of current-current correlations, which in turn, can be related to density-density correlations. Within linear response theory, these can be interpreted as response of the isolated system in the thermodynamic limit to some particular kinds of perturbations. The second way to calculate the transport coefficients is to consider the system connected to two baths at two ends. The baths are assumed to be at slightly different temperatures and chemical potentials. The energy and the particle currents in the non-equilibrium steady state (NESS) are calculated, which, in linear response regime, give the elements of the Onsager matrix. The question I ask and answer is, what is the relation between these two different ways of calculating the transport coefficients? To answer this question, I first derive the current fluctuation-dissipation relations for a general open system (no Markovian approximation, no weak-system bath coupling approximation, interacting in general) under small temperature and chemical potential biases. These relate the currents in NESS in linear response regime to current fluctuations of the open system in equilibrium. Then, I show that the two different ways of calculating the transport coefficients are actually related by a change in the order of taking the long-time and the thermodynamic limits
Presented by
Archak Purkayastha
Institution
School of Physics, Trinity College Dublin.
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Available Oct 21 between 12-4 pm.

Thermodynamics of minimal-coupling quantum heat engines

Marcin Łobejko

Abstract
The minimal-coupling quantum heat engine is a thermal machine consisting of an explicit energy storage system, heat baths, and a working body, which couples alternatively to subsystems through discrete strokes - energy-conserving two-body quantum operations. Within this paradigm, we present a general framework of quantum thermodynamics, where a process of the work extraction is fundamentally limited by a flow of non-passive energy (ergotropy), while energy dissipation is expressed through a flow of passive energy. Our main result is finding the optimal efficiency and work production per cycle within the whole class of irreversible minimal-coupling engines composed of three strokes and with the two-level working body, where we take into account all possible quantum correlations between the working body and the battery. One of the key new tools is the introduced 'control-marginal state' - one which acts only on a working body Hilbert space but encapsulates all the features of total working body-battery system regarding work extraction. https://arxiv.org/abs/2003.05788
Presented by
Marcin Lobejko <marcin.lobejko@ug.edu.pl>
Institution
Univeristy of Gdansk, Institute of Theoretical Physics and Astrophysics
Hashtags
#QuantumHeatEngines #ThermalOperations #TranslationalInvariance #IrreversibleEngines #StepEngines
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Available October 21 (Wednesday) 12:00-16:00

Two qubits engine fueled by entanglement and local measurement

Léa Bresque, Patrice A. Camati, Spencer Rogers, Kater Murch, Andrew N. Jordan, Alexia Auffèves

Abstract
We introduce a two-qubit engine that is powered by entangling operations and projective local quantum measurements. Energy is extracted from the detuned qubits coherently exchanging a single excitation. This engine, which uses the information and back-action of the measurement, is generalized to an N -qubit chain. We show that by gradually increasing the energy splitting along the chain, the initial low energy of the first qubit can be up-converted deterministically to an arbitrarily high energy at the last qubit by successive neighbor swap operations and local measurements. Modeling the local measurement as the entanglement of a qubit with a meter, we identify the measurement fuel as the energetic cost to erase correlations between the qubits.
Presented by
Léa Bresque
Institution
Institut Néel
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Available Wed 21 12h 16h CEST