Charge noise and spin noise in a semiconductor quantum device

TL;DR

This paper investigates charge and spin noise in semiconductor quantum devices using resonance fluorescence, revealing how noise impacts quantum coherence and demonstrating high-frequency operation to achieve transform-limited linewidths.

Contribution

It introduces a minimally-invasive probe to distinguish charge and spin noise in quantum dots and derives their noise spectra, advancing understanding of decoherence mechanisms.

Findings

Charge noise spectrum described by localized charge defect fluctuations

Demonstration of transform-limited linewidths above 50 kHz

Distinct optical signatures for charge and spin noise

Abstract

Solid-state systems which mimic two-level atoms are being actively developed. Improving the quantum coherence of these systems, for instance spin qubits or single photon emitters using semiconductor quantum dots, involves dealing with noise. The sources of noise are inherent to the semiconductor and are complex. Charge noise results in a fluctuating electric field, spin noise in a fluctuating magnetic field at the location of the qubit, and both can lead to dephasing and decoherence of optical and spin states. We investigate noise in an ultra-pure semiconductor using a minimally-invasive, ultra-sensitive, local probe: resonance fluorescence from a single quantum dot. We distinguish between charge noise and spin noise via a crucial difference in their optical signatures. Noise spectra for both electric and magnetic fields are derived. The noise spectrum of the charge noise can be fully described by the fluctuations in an ensemble of localized charge defects in the semiconductor. We demonstrate the "semiconductor vacuum" for the optical transition at frequencies above 50 kHz: by operating the device at high enough frequencies, we demonstrate transform-limited quantum dot optical linewidths.