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## Publications

Publications (53)

Open quantum systems that comply with detailed balance exponentially decay to thermal equilibrium. Beyond the weak coupling limit, systems that break microreversibility (e.g., in the presence of magnetic fields) violate detailed balance but still thermalize. We study the thermalization of these systems and show that a temperature rise produces nove...

It has been claimed that no protocol for measuring quantum work can satisfy standard physical principles, casting doubts on the compatibility between quantum mechanics, thermodynamics, and the classical limit. In this Letter, we present a solution for this incompatibility. We demonstrate that the standard formulation of these principles fails to ad...

We consider the dynamics of a quantum system immersed in a dilute gas at thermodynamic equilibrium using a quantum Markovian master equation derived by applying the low-density limit technique. It is shown that the Gibbs state at the bath temperature is always stationary while the detailed balance condition at this state can be violated beyond the...

We consider the dynamics of a quantum system immersed in a dilute gas at thermodynamics equilibrium using a quantum Markovian master equation derived by applying the low-density limit technique. It is shown that the Gibbs state at the bath temperature is always stationary while the detailed balance condition at this state can be violated beyond the...

Engines are open systems that can generate work cyclically at the expense of an external disequilibrium. They are ubiquitous in nature and technology, but the course of mathematical physics over the last 300 years has tended to make their dynamics in time a theoretical blind spot. This has hampered the usefulness of statistical mechanics applied to...

Engines are open systems that can generate work cyclically, at the expense of an external disequilibrium. They are ubiquitous in nature and technology, but the course of mathematical physics over the last 300 years has tended to make their dynamics in time a theoretical blind spot. This has hampered the usefulness of statistical mechanics applied t...

We introduce the “leaking elastic capacitor” (LEC) model, a nonconservative dynamical system that combines simple electrical and mechanical degrees of freedom. We show that an LEC connected to an external voltage source can be destabilized (Hopf bifurcation) due to positive feedback between the mechanical separation of the plates and their electric...

We propose a dynamical picture of how the chemical energy stored in a battery generates the electromotive force (emf). The emf is a non-electrostatic phenomenon that drives charge separation and maintains the circulation of electric current around a closed circuit when a load is attached to the battery's terminals. We show that the electrochemical...

The leaking elastic capacitor (LEC) is a non-conservative dynamical system that combines electrical and mechanical degrees of freedom. We show analytically that a LEC connected to an external voltage source can become dynamically unstable (Hopf bifurcation) due to positive feedback between the mechanical separation of the plates and their electrica...

The occurrence of any physical process is restricted by the constraints imposed by the laws of thermodynamics on the energy and entropy exchange involved. A prominent class of processes where thermodynamic constraints are crucial involve polarization of nuclear spin baths that are at the heart of magnetic resonance imaging, nuclear magnetic resonan...

Spin bath polarization is the key to enhancing the sensitivity of quantum sensing and information processing. Significant effort has been invested in identifying the consequences of quantumness and its control for spin-bath polarization. Here, by contrast, we focus on the adverse role of quantum correlations (entanglement) in a spin bath that can i...

The promise of the field of single-molecule electronics is to reveal a new class of quantum devices that leverages the strong electronic interactions inherent to sub-nanometer scale systems. Here, we form Au-molecule-Au junctions using a custom scanning tunneling microscope and explore charge transport through current-voltage measurements. We focus...

The power and efficiency of many-body heat engines can be boosted by performing cooperative nonadiabatic operations in contrast to the commonly used adiabatic implementations. Here the key property relies on the fact that nonadiabaticity is required in order to allow for cooperative effects that can use the thermodynamic resources only present in t...

Studies of emerging photovoltaics, such as organic and perovskite solar cells, have recently shown that the separation of photo-generated charge carriers is correlated with non-thermal, coherent oscillations within the illuminated device. We consider this experimental evidence in light of results from the theory of open quantum systems that point t...

The power and efficiency of many-body heat engines can be boosted by performing cooperative non-adiabatic operations in contrast to the commonly used adiabatic implementations. Here, the key property relies on the fact that non-adiabaticity is required in order to allow for cooperative effects, that can use the thermodynamic resources only present...

The aim of this book chapter is to indicate how quantum phenomena are affecting the operation of microscopic thermal machines, such as engines and refrigerators. As converting heat to work is one of the fundamental concerns in thermodynamics, the platform of quantum-thermal machines sheds light on thermodynamics in the quantum regime. This chapter...

Pedot:
PSS, a transparent electrically conductive polymer, finds widespread use in electronic devices. While empirical efforts have increased conductivity, a detailed understanding of the coupled electronic and morphological landscapes in PEDOT:PSS has lagged due to substantial structural heterogeneity on multiple length-scales. We use an optical...

We demonstrate the possiblity to cool nanoelectronic systems in nonequilibrium situations by increasing the temperature of the environment. Such cooling by heating is possible for a variety of experimental conditions where the relevant transport-induced excitation processes become quenched and deexcitation processes are enhanced upon an increase of...

The aim of this book chapter is to indicate how quantum phenomena are affecting the operation of microscopic thermal machines, such as engines and refrigerators. As converting heat to work is one of the fundamental concerns in thermodynamics, the platform of quantum thermal machines sheds light on thermodynamics in the quantum regime. This chapter...

Significance
We propose a paradigm of heat-powered maser. In contrast to textbook knowledge, it does not require population inversion or coherent driving and hence can operate with a two-level working medium. Therefore, it is a conceptually different type of maser and, more generally, a conceptually different quantum heat machine. Its autonomous ch...

Modeling nuclear quantum effects is required for accurate molecular dynamics (MD) simulations of molecules. The community has paid special attention to water and other biomolecules that show hydrogen bonding. Standard methods of modeling nuclear quantum effects like Ring Polymer Molecular Dynamics (RPMD) are computationally costlier than running cl...

Quantization of energy is a quintessential characteristic of quantum systems. Here we analyze its effects on the operation of Otto cycle heat machines and show that energy quantization alone may alter and increase machine performance in terms of output power, efficiency, and even operation mode. Our results demonstrate that quantum thermodynamics e...

The realization of molecular-based electronic devices depends to a large extent on the ability to mechanically stabilize the involved molecular bonds, while making use of efficient resonant charge transport through the device. Resonant charge transport can induce vibrational instability of molecular bonds, leading to bond rupture under a bias volta...

We analyze standard theoretical models of solar energy conversion developed to study solar cells and photosynthetic systems. We show that the assumption that the energy transfer to the reaction center/electric circuit is through a decay rate or "sink", is in contradiction with the second law of thermodynamics. We put forward a thermodynamically con...

Highly doped Poly(3,4-ethylenedioxythiophene) or PEDOT is a conductive polymer with a wide range of applications in energy conversion due to its ease of processing, optical properties and high conductivity. The latter is influenced by processing conditions, including formulation, annealing, and solvent treatment of the polymer, which also affects t...

Diverse models of engines energised by quantum-coherent, hence non-thermal, baths allow the engine efficiency to transgress the standard thermodynamic Carnot bound. These transgressions call for an elucidation of the underlying mechanisms. Here we show that non-thermal baths may impart not only heat, but also mechanical work to a machine. The Carno...

A solar cell is a heat engine, but textbook treatments are not wholly satisfactory from a thermodynamic standpoint, since they present solar cells as directly converting the energy of light into electricity, and the current in the circuit as maintained by an electrostatic potential. We propose a thermodynamic cycle in which the gas of electrons in...

Solar cells are engines converting energy supplied by the photon flux into
work. Any type of engine is also a self-oscillating system which yields a
periodic motion at the expense of a usually non-periodic source of energy. This
aspect is absent in the existing descriptions and the main goal of this paper
is to show that plasma oscillations provide...

Standard heat machines (engine, heat pump, refrigerator) are composed of a
system ("working fluid") coupled to at least two equilibrium baths at different
temperatures and periodically driven by an external device (piston or rotor)
called sometimes work reservoir. The aim of this paper is to go beyond this
scheme by considering environments which a...

We revisit the thermodynamic bounds of work extraction in simple quantum heat machines subject to control by frequent modulations that do not comply with adiabatic assumptions. The laws of thermodynamics are obeyed, yet anomalous deviations from the known bounds are revealed.

We explore means of maximizing the power output of a heat engine based on a periodically-driven quantum system that is constantly coupled to hot and cold baths. It is shown that the maximal power output of such a heat engine whose "working fluid" is a degenerate V-type three-level system is that generated by two independent two-level systems. Hence...

We analyse the operation principles and performance bounds of quantum engines
whose working fluid (WF) is energised by a non-thermal bath. We show that such
a bath (e.g., a squeezed or coherently displaced thermal bath) can render the
WF state non-passive, i.e., capable of storing and delivering work. This
non-passivity converts the heat engine int...

We present the general theory of a quantum heat machine based on an $N$-level
system (working medium) whose $N-1$ excited levels are degenerate, a
prerequisite for steady-state interlevel coherence. Our goal is to find out: To
what extent is coherence in the working medium an asset for heat machines? The
performance bounds of such a machine are com...

Quantum heat machines (QHMs) models generally assume a weak coupling to the
baths. This supposition is grounded in the separability principle between
systems and allows the derivation of the evolution equation for this case. In
the weak coupling regime, the machine's output is limited by the coupling
strength, restricting their application. Seeking...

In this review the debated rapport between thermodynamics and quantum
mechanics is addressed in the framework of the theory of
periodically-driven/controlled quantum-thermodynamic machines. The basic model
studied here is that of a two-level system (TLS), whose energy is periodically
modulated while the system is coupled to thermal baths. When the...

We explore, theoretically and experimentally, a method for cooling a
broadband heat reservoir, via its laser-assisted collisions with two-level
atoms followed by their fluorescence. This method is shown to be advantageous
compared to existing laser-cooling methods in terms of its cooling efficiency,
the lowest attainable temperature for broadband b...

We analyze a heat machine based on a periodically-driven quantum system
permanently coupled to hot and cold baths. It is shown that the maximal power
output of a degenerate $V$-type three-level heat engine is that generated by
two independent two-level systems. For $N$ levels, this maximal enhancement is
$(N-1)$-fold. Hence, level degeneracy is a t...

We analyze work extraction from an autonomous (self-contained) heat-powered
optomechanical setup. The initial state of the quantized mechanical oscillator
plays a key role. As the initial mean amplitude of the oscillator decreases,
the resulting efficiency increases. In contrast to laser-powered self-induced
oscillations, work extraction from a bro...

We explore the dependence of the performance bounds of heat engines and refrigerators on the initial quantum state and the subsequent evolution of their piston, modeled by a quantized harmonic oscillator. Our goal is to provide a fully quantized treatment of self-contained (autonomous) heat machines, as opposed to their prevailing semiclassical des...

We review the effects of frequent, impulsive quantum nondemolition measurements of the energy of two-level systems, alias qubits, in contact with a thermal bath. The resulting entropy and temperature of the system subject to measurements at intervals below the bath memory (Markovianity) time are completely determined by the measurement rate. Namely...

We investigate heat-pumped single-mode amplifiers of quantized fields in
high-Q cavities based on non-inverted two-level systems. Their power generation
is shown to crucially depend on the capacity of the quantum state of the field
to accumulate useful work. By contrast, the energy gain of the field is shown
to be insensitive to its quantum state....

We investigate the principles of autonomous quantized machines that may
operate in a dual mode: as "compression" or "absorption" refrigerators. The
operation mode is determined by the initial quantum state of the piston. Its
coefficient of performance may surpass the classical bound, while adhering to
the second law. These general results are illus...

We investigate heat-pumped lasers or masers based on non-inverted
two-level systems in high-Q cavities. Their efficiency bound is shown to
crucially depend on the capacity of their quantum state to accumulate
useful work. By contrast, the energy gain is shown to be insensitive to
the quantum state.

Work extraction from a heat engine in a cycle by a quantum mechanical device
(quantum "piston") is analyzed. The standard definition of work fails in the
quantum domain. The correct extractable work and its efficiency bound are shown
to crucially depend on the initial quantum state of the piston. The transient
efficiency bound may exceed the standa...

In traditional thermodynamics the Carnot cycle yields the ideal performance bound of heat engines and refrigerators. We propose and analyze a minimal model of a heat machine that can play a similar role in quantum regimes. The minimal model consists of a single two-level system with periodically modulated energy splitting that is permanently, weakl...

The recently developed technique combining the weak coupling limit with the
Floquet formalism is applied to a model of two-level atom driven by a strong
laser field and weakly coupled to heat baths. Firstly, the case of a single
electromagnetic bath at zero temperature is discussed and the formula for
resonance fluorescence is derived. The expressi...

We show that frequent nondemolition measurements of a quantum system immersed
in a thermal bath allow the extraction of work in a closed cycle from the
system-bath interaction (correlation) energy, a hitherto unexploited work
resource. It allows for work even if no information is gathered or the bath is
at zero temperature, provided the cycle is wi...

A minimal model of a quantum refrigerator (QR), i.e. a periodically
phase-flipped two-level system permanently coupled to a finite-capacity bath
(cold bath) and an infinite heat dump (hot bath), is introduced and used to
investigate the cooling of the cold bath towards the absolute zero (T=0).
Remarkably, the temperature scaling of the cold-bath co...

We present a short derivation and discussion of the master equation for an
open quantum system weakly coupled to a heat bath and then its generalization
to the case of with periodic external driving based on the Floquet theory.
Further, a single heat bath is replaced by several ones. We present also the
definition of heat currents which satisfies t...

We show that quantum particles constrained to move along curves undergoing cyclic deformations acquire, in general, geometric phases. We treat explicitly an example, involving particular deformations of a circle, and ponder on potential applications.

Initialization of quantum logic operations makes it imperative to cool down the information-carrying qubits as much and as fast as possible, so as to purify their state, or at least their ensemble
average. Yet, the limit on the speed of existing cooling schemes is either the duration of the qubit equilibration with its
bath or the decay time of an...

Quantum two-state systems, known as quantum bits (qubits), are unavoidably in contact with their uncontrolled thermal environment, also known as a macroscopic 'bath'. The higher the temperature of the qubits, the more impure their quantum state and the less useful they are for coherent control or quantum logic operations, hence the desirability of...