A Study Of Cold-atom Quantum Battery Based On Impurity-doped Bose-Einstein Condensate

A quantum battery(QB)is a quantum mechanical system which behaves as an efficient energy storage device which uses nonclassical effects such as quantum coherence or quantum correlation to impart an advantage compared with classical batteries.In this thesis we propose a static and dynamic cold atom QB model and study their quantum charging processes.The main results of the thesis are included as follows.1.We propose a static cold atom QB model based on an impurity-doped Bose-Einstein condensate(BEC).Two-level impurity atoms act as a BEC-assisted QB which is charged through an external static(time-indpendent)magnetic field.Energy of the external magnetic field is transferred to impurity excitations to realize energy storage in the QB.One can control the QD by the use of BEC since the energy splitting of two-level impurity atoms can be manipulated through changing impurity-BEC interaction strength.2.We study the quantum charging process of the static cold atom QB model without the initial quantum coherence of the impurities and BEC,and obtain analytical expressions of the storage capacity and the average charing power of the QB.It is shown that the storage capacity and the average charing power depend on characteristics of the impurities,the BEC,the magnetic field,and their interaction.It is found that the average charing power can be enhanced by increasing the number of the condensed atoms and/or the magnetic field.It is indicated that the fully charging status of the QB can be reached through controlling the impurity-BEC interaction strength.3.We study the quantum charging process of the static cold atom QB model with the initial quantum coherence of the impurities and BEC,and calculate the storage capacity for three types of the initial states of the QB model.It is found that quantum entanglement between impurities and BEC can enhance the storage capacity of the QB while the initial quantum coherence of the BEC may decrease the storage capacity.4.We extend the static cold atom QB model to the dynamic cold atom QB model with a time-dependent charging magnetic field,and present an analytic solution of the dynamic cold atom QB model.We obtain analytic expressions of the storage capacity and the average charing power of the QB.It is found that the dynamic QB can exhibit more quantum advantages over the static QB on the storage capacity and the average charing power.It is indicated that the fully charging status of the QB can be reached through controlling the frequency of the driving magnetic field.