Joint fluctuation theorems for sequential heat exchange

Sequential Strong Measurements and Heat Vision

We study scenarios where a finite set of non-demolition von-Neumann measurements are available. We note that, in some situations, repeated application of such measurements allows estimating an infinite number of parameters of the initial quantum state, and illustrate the point with a physical example. We then move on to study how the system under observation is perturbed after several rounds of projective measurements. While in the finite dimensional case the effect of this perturbation always saturates, there are some instances of infinite dimensional systems where such a perturbation is accu…

Beyond heat baths: Generalized resource theories for small-scale thermodynamics

Thermodynamics has recently been extended to small scales with resource theories that model heat exchanges. Real physical systems exchange diverse quantities: heat, particles, angular momentum, etc. We generalize thermodynamic resource theories to exchanges of observables other than heat, to baths other than heat baths, and to free energies other than the Helmholtz free energy. These generalizations are illustrated with "grand-potential" theories that model movements of heat and particles. Free operations include unitaries that conserve energy and particle number. From this conservation law an…

Measuring the heat exchange of a quantum process

Very recently, interferometric methods have been proposed to measure the full statistics of work performed on a driven quantum system [Dorner et al. Phys. Rev. Lett. 110 230601 (2013)] and [Mazzola et al. Phys. Rev. Lett. 110 230602 (2013)]. The advantage of such schemes is that they replace the necessity to make projective measurements by performing phase estimation on an appropriately coupled ancilla qubit. These proposals are one possible route to the tangible experimental exploration of quantum thermodynamics, a subject which is the centre of much current attention due to the current contr…

On the contribution of work or heat in exchanged energy via interaction in open bipartite quantum systems

In this paper, unambiguous redefinitions of heat and work are presented for quantum thermodynamic systems. We will use genuine reasoning based on which Clausius originally defined work and heat in establishing thermodynamics. The change in the energy which is accompanied by a change in the entropy is identified as heat, while any change in the energy which does not lead to a change in the entropy is known as work. It will be seen that quantum coherence does not allow all the energy exchanged between two quantum systems to be only of the heat form. Several examples will also be discussed. Final…

Heat-exchange statistics in driven open quantum systems

As the dimensions of physical systems approach the nanoscale, the laws of thermodynamics must be reconsidered due to the increased importance of fluctuations and quantum effects. While the statistical mechanics of small classical systems is relatively well understood, the quantum case still poses challenges. Here we set up a formalism that allows to calculate the full probability distribution of energy exchanges between a periodically driven quantum system and a thermalized heat reservoir. The formalism combines Floquet theory with a generalized master equation approach. For a driven two-level…

Functional Integral approach to time-dependent heat exchange in open quantum systems: general method and applications

We establish the path integral approach for the time-dependent heat exchange of an externally driven quantum system coupled to a thermal reservoir. We derive the relevant influence functional and present an exact formal expression for the moment generating functional which carries all statistical properties of the heat exchange process for general linear dissipation. The general method is applied to the time-dependent average heat transfer in the dissipative two-state system. We show that the heat can be written as a convolution integral which involves the population and coherence correlation …

Nonequilibrium fluctuations in quantum heat engines: Theory, example, and possible solid state experiments

We study the stochastic energetic exchanges in quantum heat engines. Due to microreversibility, these obey a fluctuation relation, called the heat engine fluctuation relation, which implies the Carnot bound: no machine can have an efficiency larger than Carnot's efficiency. The stochastic thermodynamics of a quantum heat engine (including the joint statistics of heat and work and the statistics of efficiency) is illustrated by means of an optimal two-qubit heat engine, where each qubit is coupled to a thermal bath and a two-qubit gate determines energy exchanges between the two qubits. We disc…

能量交换的广义量子涨落定理

Generalized Quantum Fluctuation Theorem for Energy Exchange

针对弱耦合下Jarzynski-Wójcik涨落定理的局限，本文通过非马尔可夫动力学建立了适用于任意耦合强度的能量交换广义量子涨落定理，为设计高效量子热机奠定基础。

Thermal production, protection and heat exchange of quantum coherences

We consider finite sized atomic systems with varying number of particles which have dipolar interactions among them and also under the collective driving and dissipative effect of thermal photon environment. Focusing on the simple case of two atoms, we investigate the impact of different parameters of the model on the coherence contained in the system. We observe that even though the system is initialized in a completely incoherent state, it evolves to a state with a finite amount of coherence and preserve that coherence in the long-time limit in the presence of thermal photons. We propose a n…

交换对称性如何影响集体量子热机的性能

How exchange symmetry impacts performance of collective quantum heat engines

该研究对比了不同交换对称性下三能级脉泽热机的集体与单粒子性能，发现玻色子对称性并非始终最优，集体功提取可超出激射温度窗口，为集体量子器件设计提供了新视角。

Analogy of RKKY oscillations to the heat exchange in cold atoms

An oscillatory term is found in both the energy expectation and dynamics of a wave-packet in a time-varying harmonic trap and infinite potential well. They are proved to oscillate in coherence with the time lapse within each period depending on both the cutoff in transition energies and the specific route via which the potential is being varied. This oscillatory term is general to arbitrary potential forms since it derives from the interference between crossed transition trajectories. Close analogy is made to the Ruderman-Kittel-Kasuya-Yosida interaction for giant-magnetoresistance trilayers, …