蓝移阱中单个铯原子基态磁不敏感态的相干操控

单个中性原子的超精细微波跃迁能级的相干性是基于中性原子量子计算、量子信息处理和量子模拟的基础.我们在实验上利用微波双光子拉曼过程实现了蓝移阱中铯原子基态超精细态|6S1/2,F=3,mF=-1〉和|6S1/2,F=4,mF=1〉间的相干操控,并研究了其相对能级频移随磁场的变化,获得了"魔术"磁场的大小为1.4(2)Gauss(1 Gauss=10-4 T).结果表明,利用魔术磁场可大幅改善超精细态|6S1/2,F=3,mF=-1?和|6S1/2,F=4,mF=1〉之间的相干性,测量到的相干时间可达1.0(1)s.

Measurement of magnetically insensitive state coherent time in blue dipole trap

Qubit encoded in single neutral atoms is a basic experimental platform for studying the quantum computation,quantum information processing and quantum simulation.The extension of the coherence time has been an important task in recent years.On the basis of the single cesium neutral atom trapped in blued-detuned dipole trap,we study the coherence time of a qubit,which is encoded in a pair of magnetically insensitive ground states of cesium atom(|0〉=|6S1/2,F=3,m F=-1〉and|1〉=|6S1/2,F=4,m F=+1〉),in the"magic"magnetic field condition.By adopting a two-photon process,in which a microwave photon and an RF photon are used,we obtain the coherence manipulation of the qubit.The dependence of differential energy shift on magnetic field is experimentally studied,and the"magic"magnetic field is determined.In this magic condition,the first derivative of differential energy shift between|0〉=|6S1/2,F=3,m F=-1〉and|1〉=|6S1/2,F=4,m F=+1〉in quantized magnet field is zero,which means that the qubit is immune to the fluctuation of magnetic field and the coherence time can be substantially prolonged.The experimentally obtained magic magnetic field is B=1.4(2)Gauss,which is in good agreement with the theoretical calculation value B=1.393 Gauss.Finally,we measure the qubit coherence time by setting the quantized magnetic field to be at magic point B=1.396 Gauss.The qubit coherence time is measured to be 11(1)ms by Ramsey interferometer,where the main decoherence factor is the inhomogeneous dephasing due to the atomic motion in the dipole trap.This incoherence factor can be dramatically suppressed by a spin-echo process where an additionalπ-pulse is inserted in between the twoπ/2 pulses.At the magic magnetic point the qubit coherence time can be extended to 1 s by the spin-echo method.