相干时间超过10 min的单离子量子比特

能够长时间储存量子信息的量子存储设备是实现大规模量子计算和量子通信的基本要素.与其他量子计算平台相比,囚禁离子系统的优势之一在于具有很长的相干时间.此前,基于囚禁离子的单量子比特相干时间不到1 min.研究发现,在囚禁离子系统中,限制量子比特相干时间的主要因素是运动能级加热和环境噪声,其中后者包含环境磁场涨落和微波相位噪声.在同时囚禁171Yb+离子和138Ba+离子的混合囚禁系统中,通过实施协同冷却和动力学解耦,可以实现相干时间超过10 min的单离子量子比特.这一技术有望用于实现量子密码学和搭建混合量子计算平台.

Single-ion qubit with coherence time exceeding 10 minutes

Quantum memory device capable of storing quantum information for a long period of time is one of the fundamental ingredients to realize large-scale quantum computation and quantum communication. Comparing with other quantum computation platforms, one of the advantages of the trapped-ion system is the long intrinsic coherence time. Before our work, the longest single-qubit coherence time in trapped-ion systems has been achieved to be less than 1 minute. It is discovered that the main limitation for the coherence time is the motional mode heating and the environment noise that includes the contributions from the magnetic field fluctuation and the phase noise of the microwaves. In a hybrid trapping system simultaneously trapping ¹⁷¹Yb⁺ and ¹³⁸Ba⁺ ions, single-qubit quantum memories with coherence time longer than 10 minutes can be realized by applying sympathetic cooling and dynamical decoupling. This technique may have some value as the building blocks for quantum cryptography protocols and hybrid quantum computation platforms.