Dephasing and leakage dynamics of noisy Majorana-based qubits: Topological versus Andreev
Dephasing and leakage dynamics of noisy Majorana-based qubits: Topological versus Andreev
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DOI：
10.1103/physrevb.101.075404
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发表时间：
2019-11
影响因子：
3.7
通讯作者：
R. Mishmash;B. Bauer;F. Oppen;J. Alicea
中科院分区：
文献类型：
--
作者：
R. Mishmash;B. Bauer;F. Oppen;J. Alicea
拓扑量子计算通过使距离为L的非阿贝尔任意子成核来非局部地编码量子信息，通常跨越量子比特设备的大小。这种非局部性使得拓扑量子比特指数免疫从所有来源的经典噪声与运营商支持本地的规模$L$的退相。我们进行详细的分析和数值分析的时域拉姆齐型协议的噪声马约拉纳为基础的量子位，旨在验证这种令人垂涎的拓扑保护在近期的设备，如所谓的'tetron'设计。通过评估失相时间对可调参数的依赖性，例如，磁场，我们提出的协议可以清楚地区分一个真正的马约拉纳量子比特从一个半局域Andreev束缚态，否则可以密切模仿真实的拓扑场景在本地探针构建。此外，我们分析了泄漏的量子位出其低能量流形由于经典噪声诱导产生的准粒子激发;泄漏限制量子位寿命时，散装间隙崩溃，因此我们的协议进一步揭示了拓扑相变的发病。这个实验需要测量两个附近的马约拉纳模式的初始化和读出-可实现的，例如，通过隧道耦合到附近的量子点-但没有进一步的马约拉纳操作，因此构成了一个诱人的预编织实验。沿着的方式，我们解决概念上的微妙之处时，讨论失相和泄漏的背景下，马约拉纳量子位。
Topological quantum computation encodes quantum information nonlocally by nucleating non-Abelian anyons separated by distances $L$, typically spanning the qubit device size. This nonlocality renders topological qubits exponentially immune to dephasing from all sources of classical noise with operator support local on the scale of $L$. We perform detailed analytical and numerical analyses of a time-domain Ramsey-type protocol for noisy Majorana-based qubits that is designed to validate this coveted topological protection in near-term devices such as the so-called `tetron' design. By assessing dependence of dephasing times on tunable parameters, e.g., magnetic field, our proposed protocol can clearly distinguish a bona fide Majorana qubit from one constructed from semilocal Andreev bound states, which can otherwise closely mimic the true topological scenario in local probes. In addition, we analyze leakage of the qubit out of its low-energy manifold due to classical-noise-induced generation of quasiparticle excitations; leakage limits the qubit lifetime when the bulk gap collapses, and hence our protocol further reveals the onset of a topological phase transition. This experiment requires measurement of two nearby Majorana modes for both initialization and readout---achievable, for example, by tunnel coupling to a nearby quantum dot---but no further Majorana manipulations, and thus constitutes an enticing pre-braiding experiment. Along the way, we address conceptual subtleties encountered when discussing dephasing and leakage in the context of Majorana qubits.