Decoherence of nuclear spins in the frozen core of an electron spin
Decoherence of nuclear spins in the frozen core of an electron spin
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电子自旋冻结核心中核自旋的退相干
DOI：
10.1103/physrevb.91.214303
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发表时间：
2015
影响因子：
3.7
通讯作者：
Guichard R
中科院分区：
文献类型：
--
作者：
Guichard R
混合量子比特系统结合了电子自旋和邻近（“邻近”）的核自旋寄存器，为量子信息处理提供了一条有前途的途径，甚至最近在钻石中展示了多自旋纠错协议。然而，对于低温硅中施主原子自旋提供的重要平台，近核自旋的退相干机制还没有很好的理解。部分原因是因为邻近的自旋位于所谓的“冻结核”区域内，在该区域中，施主电子超精细相互作用强烈抑制了核动力学。我们研究了在施主电子周围的冻结核外和冻结核内的量子自旋池中产生的中心近核量子比特的退相干，考虑了冻结核外由许多弱贡献对组成的非常大的核自旋池（“远池”）的影响。我们还提出，可能有一个重要的贡献，从几个（100阶）对称定位的核自旋对（“等价对”），这是以前没有考虑，因为它们的影响是可以忽略不计的冷冻核心外。如果等效对代表了一个可测量的退相干源，那么核相干衰变就可以提供电子波函数对称性的灵敏探测器。对于磷施主系统，我们得到了1秒量级的远浴和等效对模型的值，证实了硅中邻近核作为超长寿命自旋量子比特的合适性。
Hybrid qubit systems combining electronic spins with nearby (“proximate”) nuclear spin registers offer a promising avenue towards quantum information processing, with even multispin error-correction protocols recently demonstrated in diamond. However, for the important platform offered by spins of donor atoms in cryogenically cooled silicon, decoherence mechanisms ofproximate nuclear spins are not yet well understood. The reason is partly because proximate spins lie within a so-called “frozen core” region where the donor electronic hyperfine interaction strongly suppresses nuclear dynamics. We investigate the decoherence of a central proximate nuclear qubit arising from quantum spin baths outside, as well as inside, the frozen core around the donor electron. We consider the effect of a very large nuclear spin bath comprising manyweakly contributing pairs outside the frozen core (the “far bath”). We also propose that there may be an important contribution from a few (of order 100) symmetrically sited nuclear spin pairs (“equivalent pairs”), which were not previously considered because their effect is negligible outside the frozen core. If equivalent pairs represent a measurable source of decoherence, nuclear coherence decays could provide sensitive probes of the symmetries of electronic wave functions. For the phosphorus donor system, we obtainvalues of order 1 second for both the far-bath and equivalent-pair models, confirming the suitability of proximate nuclei in silicon as very-long-lived spin qubits.