马约拉纳四体系统中测量诱导的X宇称寿命增强

中文摘要 AI 辅助

近期一项实验[arXiv:2507.08795]通过辅助读出点的量子电容，报道了马约拉纳四体（Majorana tetron）器件中 wire 间X宇称寿命的测量结果。受这些测量的启发，我们从理论上研究了受静电噪声影响的耦合点-四体系统最小模型中的 wire 间宇称寿命。我们表明，与测量点的耦合本身可通过产生能量劈裂，将噪声诱导的跃迁移至有限频率，从而使被测态免受低频涨落的影响，强烈改变宇称动力学。对于受无序纳米线器件启发的代表性噪声强度，我们发现，即使裸四体的相干时间仅为几十纳秒，在测量配置下X宇称的切换寿命也达到微秒量级。我们分析了两种情况：色散区，其中点可被积分掉，动力学简化为有效二能级系统；近共振区，其中所有四个低能态都参与其中。在后一种情况中，快速跃迁将谱组织为两个长寿命的流形，近似对应耦合点-四体X环宇称的扇区，尽管存在潜在的多能级结构，仍产生有效二态切换。我们的结果表明，测量诱导的稳定作用可显著增强观测到的X宇称切换寿命，使得连续读出下测量的寿命可大大超过孤立马约拉纳四体量子比特的本征空闲T₂*相干时间。

英文摘要

A recent experiment [arXiv:2507.08795] has reported measurements of the interwire $X$-parity lifetime in a Majorana tetron device via the quantum capacitance of an auxiliary readout dot. Motivated by these measurements, we theoretically study the interwire parity lifetime in a minimal model of the coupled dot-tetron system subject to electrostatic noise. We show that coupling to the measurement dot can itself strongly modify the parity dynamics by generating an energy splitting that shifts noise-induced transitions to finite frequency and thereby stabilizes the measured states against low-frequency fluctuations. For representative noise strengths motivated by disordered nanowire devices, we find $X$-parity switching lifetimes of order microseconds in the measurement configuration even when the corresponding bare-tetron coherence time is only tens of nanoseconds long. We analyze both the dispersive regime, where the dot can be integrated out and the dynamics reduces to an effective two-level system, and the near-resonant regime, where all four low-energy states participate. In the latter case, rapid transitions organize the spectrum into two long-lived manifolds that approximately correspond to sectors of the combined dot-tetron $X$-loop parity, yielding effective two-state switching despite the underlying multilevel structure. Our results show that measurement-induced stabilization can substantially enhance the observed $X$-parity switching lifetime, such that the lifetime measured under continuous readout can greatly exceed the intrinsic idle $T_2^*$ coherence time of the isolated Majorana tetron qubit.

发表机构

• University of Maryland（马里兰大学）

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