Research On Performance Optimization Of Quantum Otto Cycle Based On Shortcuts To Adiabaticity Technology

In the field of quantum thermodynamics,the design of efficient quantum thermal cycle is a hot topic.In order to ensure high output efficiency,the ideal thermal cycle usually includes quasi-static processes(isothermal process in Carnot cycle and adiabatic process in Otto cycle),resulting in zero output power of thermal cycle.Considering the free evolution process of finite time,although non-zero output power can be obtained,the performance of thermal cycle is not ideal due to significant heat dissipation.In this context,the shortcuts to adiabaticity(STA)technology developed by scholars in recent years has become an important means to design high-performance quantum thermal cycles.This technology aims to achieve the same dynamic evolution results as the quantum adiabatic process in a short time.Based on this,the ideal adiabatic process in the thermal cycle can be completed in a limited time,which ensures that the power can be increased while efficiency remains unchanged,so as to achieve high-performance quantum thermal cycle.Taking few body and many body quantum systems as the research objects respectively,combined with STA,the thermal cycle characteristics of the system are studied in detail.The core research contents include:1.Considering the three-qubit system as the working medium,the thermodynamic properties of the quantum Otto cycle under the transitionless quantum driving scheme are explored.It is demonstrated that the tripartite Otto cycle as a universal machine,in the suitable regimes of external control parameter,could work as a quantum heat engine(QHE),refrigerator or heat pump.In addition,the performances of QHE and refrigerator with and without STA,such as the power and efficiency of QHE and the coefficient of performance(COP)and figure of merit(FOM)of refrigerator,have been investigated.The results show that:(i)The application of STA scheme can lead to an effective enhancement in the performances of Otto cycle,including achievements of a high QHE's/refrigerator's power associated with a moderate QHE's efficiency/COP of refrigerator.(ii)Even in a short-time cycle the optimization of control parameters could arise a remarkable improvement in the efficiency(or COP)of STA QHE(refrigerator),approaching the ideal efficiency or COP of conventional Otto cycle with quasi-static process.(iii)With the aid of parameter optimization the trade-off regions between the efficiency and the power(the COP and the FOM)of STA Otto engine(refrigerator)have been advised.2.Taking the Heisenberg XX spin chain as the working medium,the thermodynamic performance of the quantum Otto heat engine under the variational approximate STA scheme is studied.Combined with the multi-body model,the analytical expression of the external driving term used to drive the approximate sta protocol is derived.In addition,the results of the efficiency and power of engine,and the fidelity of the adiabatic process by numerical simulation as follows:(i)The high fidelity of expansion process applying approximate STA protocol is achieved compared with the ideal expansion process,and the fidelity of the compression process under this protocol is several times higher than that under the free evolution scheme.(ii)Taking the evolution time of adiabatic process as a reference,STA heat engine is a general heat engine in short-time cycle,while it is a hybrid heat engine for long-time evolution.(iii)In terms of heat engine performance,STA heat engines achieve far more power and efficiency than those under the free evolution scheme,and are close to the performance of their corresponding ideal heat engines.This research shows the effectiveness of STA technology in improving the overall performance of quantum thermal cycle;At the same time,the possibility of its application in the design of many-body heat engine is also revealed.These have important reference value for the design of high-performance quantum thermodynamic machines in the future.