Quantum non-demolition measurement of an electron spin qubit through its low-energy many-body spin environment

• Main Authors: Dyte, Harry E, Gillard, George, Manna, Santanu, da Silva, Saimon F. Covre, Rastelli, Armando, Chekhovich, Evgeny A
• Format: Journal Article
• Language: English
• Published: 01-07-2023
• Subjects: Physics - Mesoscale and Nanoscale Physics; Physics - Quantum Physics
• DOI: 10.48550/arxiv.2307.00308

The measurement problem dates back to the dawn of quantum mechanics. Here, we
measure a quantum dot electron spin qubit through off-resonant coupling with
thousands of redundant nuclear spin ancillae. We show that the link from
quantum to classical can be made without any "wavefunction collapse", in
agreement with the Quantum Darwinism concept. Large ancilla redundancy allows
for single-shot readout with high fidelity $\approx99.85\%$. Repeated
measurements enable heralded initialization of the qubit and probing of the
equilibrium electron spin dynamics. Quantum jumps are observed and attributed
to burst-like fluctuations in a thermally populated phonon bath.