Rapid Single-Shot Measurement of a Singlet-Triplet Qubit

TL;DR

This paper demonstrates rapid, high-fidelity single-shot measurements of a two-electron spin state in a GaAs quantum dot, enabling real-time observation of nuclear environment dynamics.

Contribution

It introduces a measurement scheme achieving over 90% fidelity in 7 microseconds, allowing direct observation of hyperfine-induced singlet-triplet precession and nuclear environment evolution.

Findings

Measurement fidelity above 90%

Cycle time of 7 microseconds

Observation of nuclear Overhauser field dynamics

Abstract

We report repeated single-shot measurements of the two-electron spin state in a GaAs double quantum dot. The readout scheme allows measurement with fidelity above 90% with a 7 microsecond cycle time. Hyperfine-induced precession between singlet and triplet states of the two-electron system are directly observed, as nuclear Overhauser fields are quasi-static on the time scale of the measurement cycle. Repeated measurements on millisecond to second time scales reveal evolution of the nuclear environment.