High-fidelity single-shot readout for a spin qubit via an enhanced latching mechanism

TL;DR

This paper presents an enhanced latching readout method for spin qubits that achieves record high single-shot fidelity over 99.86%, with improved signal amplitude and relaxed layout constraints, advancing quantum measurement technology.

Contribution

It introduces a novel enhanced latching readout technique that significantly improves fidelity and signal strength for spin qubits, surpassing previous methods.

Findings

Achieved >99.86% single-shot fidelity with enhanced readout.

Enhanced signal amplitude to a full one-electron signal.

Relaxed layout constraints due to dipole insensitivity.

Abstract

The readout of semiconductor spin qubits based on spin blockade is fast but suffers from a small charge signal. Previous work suggested large benefits from additional charge mapping processes, however uncertainties remain about the underlying mechanisms and achievable fidelity. In this work, we study the single-shot fidelity and limiting mechanisms for two variations of an enhanced latching readout. We achieve average single-shot readout fidelities > 99.3% and > 99.86% for the conventional and enhanced readout respectively, the latter being the highest to date for spin blockade. The signal amplitude is enhanced to a full one-electron signal while preserving the readout speed. Furthermore, layout constraints are relaxed because the charge sensor signal is no longer dependent on being aligned with the conventional (2, 0) - (1, 1) charge dipole. Silicon donor-quantum-dot qubits are used for this study, for which the dipole insensitivity substantially relaxes donor placement requirements. One of the readout variations also benefits from a parametric lifetime enhancement by replacing the spin-relaxation process with a charge-metastable one. This provides opportunities to further increase the fidelity. The relaxation mechanisms in the different regimes are investigated. This work demonstrates a readout that is fast, has one-electron signal and results in higher fidelity. It further predicts that going beyond 99.9% fidelity in a few microseconds of measurement time is within reach.

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