Keeping a spin qubit alive in natural silicon: Comparing optimal working points and dynamical decoupling
Keeping a spin qubit alive in natural silicon: Comparing optimal working points and dynamical decoupling
复制标题
DOI：
10.1103/physrevb.91.245416
复制
发表时间：
2015-02
影响因子：
3.7
通讯作者：
S. J. Balian;Renbao Liu;T. S. Monteiro
中科院分区：
文献类型：
--
作者：
S. J. Balian;Renbao Liu;T. S. Monteiro
有两种不同的技术证明有效地延长自旋量子位在其他自旋环境中的相干寿命。一种是动态解耦，即量子比特受到精心定时的控制脉冲序列的影响;另一种是将量子比特调谐到“最佳工作点”（OWP），这是降低磁场退相干的最佳点。利用量子多体计算方法，研究了远离和靠近OWP的动力学退耦脉冲序列对中心施主量子比特在核自旋浴中退相干的影响。理解这种行为的关键是分析多体量子浴中独立的翻转自旋对通常占主导地位的贡献的抑制程度。我们发现，为了模拟最近测量到的Hahn回波在OWP（最低阶动力学解耦）下的衰变，必须考虑三个相互作用的自旋组成的团簇，因为独立的自旋对甚至不能给出有限的-${T}_{2}$衰变时间。我们发现，当在OWP附近工作时，动态解耦序列需要数百个脉冲才能获得${T}_{2}$的单个数量级增强，而远离OWP的制度只需要大约10个脉冲。
There are two distinct techniques of proven effectiveness for extending the coherence lifetime of spin qubits in environments of other spins. One is dynamical decoupling, whereby the qubit is subjected to a carefully timed sequence of control pulses; the other is tuning the qubit towards ``optimal working points'' (OWPs), which are sweet spots for reduced decoherence in magnetic fields. By means of quantum many-body calculations, we investigate the effects of dynamical decoupling pulse sequences far from and near OWPs for a central donor qubit subject to decoherence from a nuclear spin bath. Key to understanding the behavior is to analyze the degree of suppression of the usually dominant contribution from independent pairs of flip-flopping spins within the many-body quantum bath. We find that to simulate recently measured Hahn echo decays at OWPs (lowest-order dynamical decoupling), one must consider clusters of three interacting spins since independent pairs do not even give finite-${T}_{2}$ decay times. We show that while operating near OWPs, dynamical decoupling sequences require hundreds of pulses for a single order of magnitude enhancement of ${T}_{2}$, in contrast to regimes far from OWPs, where only about 10 pulses are required.