Study On Charging Properties Of Quantum Batteries Based On Spin Systems

A classical battery is an electrochemical device that stores energy and uses it to power a classical circuit by converting chemical energy into a sustained potential difference.Quantum battery systems can also provide energy storage for quantum systems through energy conversion or transfer.Compared with classical battery,quantum battery system is composed of two parts: battery and charger.The battery part is generally qubit,such as spin,atom and other two-level system,while the charger can be qubits like the battery,or a thermal bath or classical drive field.The charging and discharging process of quantum battery is accomplished through the coupling between battery and charger.An important topic of quantum battery research is to find the maximum available energy stored during charging by tuning the system parameters and accelerate the energy release after charging.Another research focus is the relationship between the extractable work of quantum batteries and the quantum resources such as entanglement in the battery system.Quantum batteries are generally quantum many-body systems,in which there are a lot of quantum resources such as entanglement,coherence,etc..Exploring the relationship between these quantum resources and charging performance is also a topic of recent attention.In this thesis,we mainly study the charging properties of quantum batteries under the central spin model and one-dimensional spin chain model.The thesis is divided into three chapters.The first chapter introduces some basic concepts of quantum battery and the indexes of measuring the characteristics of quantum battery.In Chapter 2,we first introduce the central spin quantum cell model,and deduce the state evolution form of the Hamiltonian in the invariant subspace.Based on the invariant subspace,we get the evolution of the battery subsystem with time.Then,the effects of different system parameters on the charging properties of the central spin quantum battery are studied in detail.It is found that the extractable power increases exponentially with the increase of the number of batteries,and increasing the interaction is a good choice to shorten the charging time.Different system parameters have different influences on the charging properties of central spin quantum batteries,but the negative correlation between entanglement and extractable work is always valid,that is,when the extractable work reaches the maximum,the entanglement of battery and charger is the minimum.The central spin quantum battery is an incoherent quantum battery.In Chapter 3,we study the charging properties of a coherent quantum battery based on a one-dimensional spin chain.It is found that photon number can improve the extractable work and the ratio of extractable work to total energy during charging of the driving field,while the advantage of thermal bath charging is that,the battery can reach the maximum energy and extractable work stably and quickly under the condition of thermal bath charging.We then investigate the dynamical evolution of two-and three-party entanglement in spin chain quantum cells.It has been shown that if we want to obtain stable two-or three-party entanglement in dissipative spin chain systems,we need to consider closed spin chain systems rather than open chains.In the last part of the paper,we summarize the main results of the research and prospect the followup research.