Charge noise and spin noise in a semiconductor quantum device

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

Two-photon interference from remote quantum dots with inhomogeneously broadened linewidths

“…In the case of semiconductor-based single-photon emitters, the mode function (ω) of the photons is subject to small variations in frequency, for example, by coupling to phonons, or charge and spin noise [27]. Here, we only assume inhomogeneous broadening, which is represented by a Gaussian frequency distribution f (ω) with σ 2 being the variance:…”

Auger Recombination in Self-Assembled Quantum Dots: Quenching and Broadening of the Charged Exciton Transition

“…Charge carriers in the vicinity of a dot lead to spectral broadening [3][4][5] . Furthermore, electron and hole interaction inside the dot enables Auger recombination, a non-radiative process, where the electron-hole recombination energy is transferred to an additional charge carrier 6,7 .…”

“…We obtain (3) directly reflects the measured transients in Fig. 2(a) with given by (4) To determine the Auger recombination rate, we use the tunneling rate , derived from pulsed measurements of the excitonic RF (see supplementary and (30)). Using a fit of Eq.…”

Two-photon interference from a quantum dot microcavity: Persistent pure dephasing and suppression of time jitter

“…The HOM measurements therefore include an effective time filter. In contrast, the measurements made using the Michelson interferometer are time integrated and, as such, long-term drifts and spectral diffusion result in a deterioration of the extracted T 2 value [7,9,39].…”