Harnessing many-body spin environment for long coherence storage and high-fidelity single-shot qubit readout

• Published in: Nature communications 2022-07, Vol.13 (1), p.4048-4048, Article 4048
• Main Authors: Gillard, George, Clarke, Edmund, Chekhovich, Evgeny A.
• Format: Article
• Language: English
• Subjects: 639/766/119/1000/1017; 639/925/927/481; Accuracy; Electron spin; Electrons; Humanities and Social Sciences; Hybrid systems; multidisciplinary; Nuclear spin; Quantum dots; Quantum phenomena; Qubits (quantum computing); Science; Science (multidisciplinary); Single electrons
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-31618-4

There is a growing interest in hybrid solid-state quantum systems where nuclear spins, interfaced to the electron spin qubit, are used as quantum memory or qubit register. These approaches require long nuclear spin coherence, which until now seemed impossible owing to the disruptive effect of the electron spin. Here we study InGaAs semiconductor quantum dots, demonstrating millisecond-long collective nuclear spin coherence even under inhomogeneous coupling to the electron central spin. We show that the underlying decoherence mechanism is spectral diffusion induced by a fluctuating electron spin. These results provide new understanding of the many-body coherence in central spin systems, required for development of electron-nuclear spin qubits. As a demonstration, we implement a conditional gate that encodes electron spin state onto collective nuclear spin coherence, and use it for a single-shot readout of the electron spin qubit with >99% fidelity. Hybrid quantum devices based on coupled nuclear and electron spins offer promising applications, but require long nuclear spin coherence times. Here the authors demonstrate millisecond coherence times for a nuclear spin ensemble coupled to a single electron spin qubit in a semiconductor quantum dot.