Quantum Heat Engine With Photon-Atom Coupling In Cavity QED System

The invention and wide spread of the heat engine have an irreplaceable effect on the progress of human history.The Carnot engine defines the highest efficiency of the classical heat engine: the reversible heat engine operating between two thermal reservoirs with certain temperatures has the highest efficiency that is only related to the temperatures of the two thermal reservoirs.Micromation and integration are the main trend in the research of the machines in decades,which makes the scales of the machine enter into the mesoscopic regime and even close to the quantum regime.That has challenged the classical working principles of the machines.Especially in their power parts,the classical heat engines based on the theory of the classical thermodynamics may not work effectively,which makes the research on the quantum heat engine a necessity.Due to the quantum characteristics of the working substance,the quantum heat engine will have many singular properties beyond the classical heat engine.However,in the theoretical research the models of the quantum heat engines are mostly based on the systems of prominent quantum properties,such as atoms,photons,and so on,aiming at exploring the foundations of thermodynamics from a quantum theory point of view.This article investigates the theory of the quantum heat engine based on the cavity QED system.Since on the one hand the cavity QED theory can be used in cavity optomechanical system,and the development of cavity QED has enabled to achieve the quantum regime of mechanical systems in an experimental setting recently,which enables the research of quantum heat engine.On the other hand,the inherent mechanical features of cavity QED system will perform good co-operations with the current machines.Those two points make the cavity QED system be a well research platform for quantum heat engine that balances the theoretical study with the practical application.In this paper,the basic knowledge of quantum heat engine is presented.We then introduce a polariton heat engine based on the coupling between a single atom and a single photon,in the command of micromation and integration of the machines.We then try to surpass the limit of the classical Carnot efficiency and propose a quantum heat engine consists of a positive absolute temperature reservoir and a negative one.The polaritonic heat engine introduced above can also be used to measure a phonon mode.The main contents of this paper are as follows:First,we simply introduce the theory of the quantum heat engine,starting with the law of quantum thermodynamics that analogous to the classical one,together with the processes of the quantum thermodynamics.The theoretical model of the quantum heat engine is then introduced,following with a brief comparison between the classical Carnot engine and the quantum one,as well as the classical Otto engine and the quantum Otto one.The theoretical model of work measurement on the quantum thermodynamics system is presented afterwards.We began to introduce such work measurement with two-time-point measurement in isolated system.The continuous quantum measurement based on quantum trajectory in open system is presented afterwards.Hybrid quantum systems can often be described in terms of polaritons.These are quasiparticles formed of superpositions of their constituents,with relative weights depending on some control parameter in their interaction.In many cases,these constituents are coupled to reservoirs at different temperatures.This suggests a general approach to the realization of polaritonic heat engines where a thermodynamic cycle is realized by tuning this control parameter.We discuss in Chapter three what is arguably the simplest such engine,a single qubit coupled to a single photon.We show that this system can extract work from feeble thermal microwave fields.We also propose a quantum measurement scheme of the work and evaluate its backaction on the operation of the engine.The improvement in the efficiency of the heat engine has been the goal pursued by physicists.We try to propose a scheme of the quantum heat engine that can surpass the limit of the classical Carnot efficiency.In chapter four,a cavity QED heat engine,in which the temperatures of the two thermal reservoirs are a positive absolute temperature and a negative one,is built.The efficiency of the heat engine consists of reservoirs with opposite sign of temperatures is larger than 1 under the classical Carnot definition.While under the first law of the thermodynamics,the ideal case of such engine can draw heat from both two reservoirs and completely converted to work,making the actual efficiency be 1.A phonon mode measurement scheme is proposed based on the above polaritonic heat engine.The polariton is a quasiparticle formed of superpositions of phonon mode and photon mode in the cavity QED system.It performs approximately almost phonon mode or photon mode at different coupling parameters,and can transforms to each other by tuning such cou-pling parameter.The “state transfer”model makes the information of the phonon mode that is meant to be measured be transferred to the phonon mode of the cavity QED system,and then evolves to a photon mode that can be measured by photon counting method.There are different most appropriate cavity QED coupling parameters for different initial states of the phonon mode that is meant to be measured.Under this most appropriate coupling parameter,the measurement limit of the system can be very high.The quantum heat engine models based on the cavity QED system and the measurement scheme of the phonon mode in this paper provide important theoretical and experimental values for the study of the heat engine.