Projective measurement of single-electron spins, or spin readout, is among the most fundamental technologies for spin-based quantum information processing. Implementing spin readout with both high-fidelity and scalability is indispensable for developing fault-tolerant quantum computers in large-scale spin-qubit arrays. To achieve high fidelity, a latching mechanism is useful. However, the fidelity can be decreased by spin relaxation and charge state leakage, and the scalability is currently challenging. Here, we propose and demonstrate a double-latching high-fidelity spin readout scheme, which suppresses errors via an additional latching process. We experimentally show that the double-latching mechanism provides significantly higher fidelity than the conventional latching mechanism and estimate a potential spin readout fidelity of 99.94% using highly spin-dependent tunnel rates. Due to isolation from error-inducing processes, the double-latching mechanism combined with scalable charge readout is expected to be useful for large-scale spin-qubit arrays while maintaining high fidelity.

单电子自旋的射影测量或自旋读数是基于自旋的量子信息处理的最基本技术之一。在大规模自旋量子比特阵列中开发容错量子计算机，实现高保真度和可扩展性的自旋读出是必不可少的。为了实现高保真度，锁存机制非常有用。然而，自旋弛豫和电荷态泄漏会降低保真度，并且可扩展性目前具有挑战性。在这里，我们提出并演示了一种双锁存高保真自旋读出方案，该方案通过额外的锁存过程抑制了错误。我们实验表明，双闭锁机制提供了比传统闭锁机制高得多的保真度，并使用高度依赖自旋的隧道速率估计潜在的自旋读出保真度为 99.94%。由于与误码诱导过程隔离，双锁存机制与可扩展的电荷读出相结合，有望在保持高保真度的同时，对大规模自旋量子比特阵列有用。