AI 中文总结
研究在耦合最小Kitaev链中实现马约拉纳宇称量子比特的相干控制。核心方法是实现两比特Kitaev链间相干耦合，利用费米子宇称守恒特性。主要贡献是展示了该量子比特，观察到相干宇称振荡并验证其与模型相符，实现了首次相干控制。
AI 中文摘要
马约拉纳零模通过在费米子宇称中进行非局部信息编码，为容错量子比特提供了一条途径。预计它们对噪声的敏感度会随着马约拉纳之间距离的增加而呈指数下降，即拓扑保护。量子点 - 超导体阵列中的Kitaev链提供了一个可调平台，即使在两比特链中，分离的马约拉纳零模也能在链的末端出现。这些最小链模式被称为穷人的马约拉纳，保留了马约拉纳的特性，但保护有限。关键挑战是超越在电输运测量中识别这些模式，实现时域中的相干量子比特控制。本文通过实现两比特Kitaev链之间的相干耦合，展示了一个马约拉纳宇称量子比特。由于总费米子宇称守恒，系统分为全局偶宇称和奇宇称流形。在马约拉纳甜点处，我们观察到两个流形中具有相等振荡频率的相干宇称振荡。我们还表明，振荡频率和相干性系统地依赖于链间耦合和量子点失谐，与我们的短、部分保护链模型密切一致。我们的结果建立了对马约拉纳量子比特的首次相干控制，该量子比特由最小Kitaev链中马约拉纳零模的费米子宇称编码。
英文摘要
Majorana zero modes provide a route to fault-tolerant qubits by encoding information non-locally in fermion parity. Their sensitivity to noise is expected to decrease exponentially with increasing separation between the Majoranas, a suppression known as topological protection. Kitaev chains engineered in quantum dot-superconductor arrays provide a tunable platform in which separated Majorana zero modes can emerge at the ends of the chain, even in two-site chains. These minimal-chain modes are known as poor man's Majoranas and retain characteristic Majorana properties, including near-zero energy and equal electron-hole character, but have only limited protection. A key outstanding challenge is to move beyond identifying such modes in electrical transport measurements and achieve coherent qubit control in the time domain. Here, we demonstrate a Majorana parity qubit by realizing coherent coupling between two-site Kitaev chains. Since total fermion parity is conserved, the system separates into global even and odd parity manifolds. We observe coherent parity oscillations in both manifolds with equal oscillation frequencies at the Majorana sweet spot, as predicted for isolated Majorana zero modes. We further show that the oscillation frequency and coherence depend systematically on inter-chain coupling and quantum-dot detunings, in close agreement with our model for short, partially protected chains. Our results establish the first coherent control of a Majorana qubit, encoded in the fermion parity of Majorana zero modes in minimal Kitaev chains.
