Stochastic Floquet quantum heat engines and stochastic efficiencies

量子力学引擎模型及其效率

Quantum-mechanical engine models and their efficiencies

基于量子热力学过程，对典型的热机循环，如卡诺循环、布雷顿循环、奥托循环和狄塞尔循环等进行了量子力学推广。这些热机循环不包括温度，因为在量子力学中能量的概念是有明确定义的，而温度\emph{a priori}不是。这些QM引擎循环是由一个理想的或相互作用的系统与任意数量的粒子限制在一个任意的幂律陷阱。结果表明，量子绝热指数与陷阱指数之间存在着一定的关系，量子绝热循环的效率与经典循环的效率相似，从而证明了量子绝热循环效率的普适性。

Engineering Floquet Dynamical Quantum Phase Transition

Floquet dynamical quantum phase transitions (FDQPTs) are signified by recurrent nonanalytic behaviors of observables in time. In this work, we introduce a quench-free and generic approach to engineer and control FDQPTs for both pure and mixed Floquet states. By applying time-periodic modulations with two commensurate driving frequencies to a general class of spin chain model, we find multiple FDQPTs within each driving period. The nonanalytic cusps of return probability form sublattice structures in time domain. Notably, the number and time-locations of these cusps can be flexibly controlled b…

Heat engine model exhibit super-universal feature and capture the efficiencies of different power plants

We propose a generalized model of a heat engine and calculate the minimum and maximum bounds on the efficiency at maximum power. We obtain a universal form of generalized extreme bounds on the efficiency at maximum power. Our model unifies the bounds on the efficiency and the universality features are observed for various heat engine models. Even though our model is a direct generalization of low-dissipation heat engines, the bounds on the efficiency obtained at a single target function capture those observed in the actual power plants working at different dissipation levels.

Lindblad-Floquet description of finite-time quantum heat engines

The operation of autonomous finite-time quantum heat engines rely on the existence of a stable limit cycle in which the dynamics becomes periodic. The two main questions that naturally arise are therefore whether such a limit cycle will eventually be reached and, once it has, what is the state of the system within the limit cycle. In this paper we show that the application of Floquet's theory to Lindblad dynamics offers clear answers to both questions. By moving to a generalized rotating frame, we show that it is possible to identify a single object, the Floquet Liouvillian, which encompasses …

量子热机的Floquet工程：一种基于梯度的性能优化谱方法

Floquet engineering of quantum thermal machines: A gradient-based spectral method to optimize their performance

本研究提出一种基于梯度的谱方法，通过优化周期性驱动的控制函数形态，寻找用马尔可夫主方程描述的开放量子系统量子热机的最优工作区间，且支持按实验或物理要求约束参数。

Reinforcement learning for autonomous preparation of Floquet-engineered states: Inverting the quantum Kapitza oscillator

I demonstrate the potential of reinforcement learning (RL) to prepare quantum states of strongly periodically driven non-linear single-particle models. The ability of Q-Learning to control systems far away from equilibrium is exhibited by steering the quantum Kapitza oscillator to the Floquet-engineered stable inverted position in the presence of a strong periodic drive within several shaking cycles. The study reveals the potential of the intra-period (micromotion) dynamics, often neglected in Floquet engineering, to take advantage over pure stroboscopic control at moderate drive frequencies. …