基于超导电路的奥特-汤恩斯分裂效应  

Superconducting-circuit based Aulter-Towns splitting effect

作　　者：吴小宇 赵虎[2] 李智[1] Wu Xiao-Yu;Zhao Hu;Li Zhi(College of Electronics and Information Engineering,Sichuan University,Chengdu 610065,China;AVIC Xi’an Automatic Control Research Institute,Xi’an 710065,China)

机构地区：[1]四川大学电子信息学院,成都610065 [2]航空工业西安飞行自动控制研究所,西安710065

出　　处：《物理学报》2020年第23期17-24,共8页Acta Physica Sinica

基　　金：国家重点基础研究发展计划(批准号:2011CBA00304);国家自然科学基金重点项目(批准号:60836001)资助的课题.

摘　　要：基于约瑟夫森结的超导量子比特是一个宏观的人工原子,通过微纳米加工的方法,可以改变人工原子的基本参数.三维Transmon量子比特是目前已知退相干时间较长的一种量子比特,该量子比特通过电容的方式与三维超导谐振腔进行耦合,是一个人造的原子与腔场耦合系统,可对原子物理、量子力学、量子光学、腔量子电动力学的各种效应进行实验验证.本文制备并实现了3D Transmon量子比特,通过Jaynes-Cummings方法寻找到了区分基态、第一激发态和第二激发态的最佳读出功率,对共振条件下和非共振条件下的奥特-汤恩斯分裂效应进行了测试表征,得到的测试结果与理论结果相符.The superconducting quantum bit(qubit)based on Josephson junction is a macroscopic artificial atom.The basic parameters of the artificial atom can be changed by micro and nano machining.The three-dimensional(3D)Transmon qubit is a kind of qubit with the longer decoherence time.It is coupled with a 3D superconducting cavity by means of capacitance.It is a man-made coupling system between atom and cavity field,which can verify the effects of atomic physics,quantum mechanics,quantum optics and cavity quantum electrodynamics.In this paper,transmon qubits are prepared by the double angle evaporation method,and coupled with aluminum based 3D superconducting resonator to form 3D transmon qubits.The basic parameters of 3D transmon are characterized at an ultra-low temperature of 10 m K.The 3D transmon parameters are EC=348.74 MHz and EJ=11.556 GHz.The coupling coefficient g2/△between qubit and the 3D cavity is 43 MHz,which is located in the dispersive regime.The first transition frequency of qubit is f01=9.2709 GHz,and the second transition frequency is f12=9.0100 GHz.The 3D resonator is made of the material 6061T6 aluminum,the loaded quality factor is 4.8×105,and the bare frequency of the resonator is 8.108 GHz.The JaynesCummings readout method is used to find the optimal readout power to distinguish among the qubit in the ground state|0>,qubit in the superposition state of|0>and|1>,and qubit in the superposition state of|0>,|1>and|2>.Then,the Aulter-Townes splitting(ATS)experiment can be fulfilled in this system.Unlike the method given by Novikov et al.[Novikov S,Robinson J E,Keane Z K,et al.2013 Phys.Rev.B 88060503],our method only needs to apply continuous microwave excitation signal to the qubit,and does not need to carry out precise timing test on the qubit,thus reducing the test complexity of observing ATS effect.The ATS effect in resonance and non-resonance regime are observed.In the resonance ATS experiment,in order to obtain the peak value and frequency of resonance peak,Lorentz curve can be used for fitting

关 键 词：三维 Transmon JAYNES-CUMMINGS 读出法 奥特-汤恩斯分裂效应 

分 类 号：O413[理学—理论物理] O562[理学—物理]