High Resolution Coherent Population Trapping on a Single Hole Spin in a Semiconductor Quantum Dot

Julien Houel,Andreas V Kuhlmann,Christopher E Kuklewicz,Brian D Gerardot,Jonathan H Prechtel,Daniel Brunner,Pierre M Petroff,Richard J Warburton,Nick G Stoltz

doi:10.1103/physrevlett.112.107401

Abstract

We report high resolution coherent population trapping on a single hole spin in a semiconductor quantum dot. The absorption dip signifying the formation of a dark state exhibits an atomic physicslike dip width of just 10MHz. We observe fluctuations in the absolute frequency of the absorption dip, evidence of very slow spin dephasing. We identify the cause of this process as charge noise by, first, demonstrating that the hole spin g factor in this configuration (in-plane magnetic field) is strongly dependent on the vertical electric field, and second, by characterizing the charge noise through its effects on the optical transition frequency. An important conclusion is that charge noise is an important hole spin dephasing process.

Highlights

We report high resolution coherent population trapping on a single hole spin in a semiconductor quantum dot
We identify the cause of this process as charge noise by, first, demonstrating that the hole spin g factor in this configuration is strongly dependent on the vertical electric field, and second, by characterizing the charge noise through its effects on the optical transition frequency
Coherent population trapping (CPT) is a quantum interference effect which arises in an optical Λ system

Summary

Spin dephasing times lie in

Week ending 14 MARCH 2014 the 10–100 ns regime with significant differences from experiment to experiment [6,19,20,21]. The experiment is very challenging: ΔR=R is very small at the optical resonance (0.1%); at the ultralow laser powers used here noise in the detector circuit is significant; and in the perturbative regime (ħΩ1 ≪ ħΩ2 ≪ ħ=τr), the width of the CPT dip approaches the limit set by the mutual coherence of the lasers. We meet these challenges with a solid immersion lens to boost the ΔR=R signal, a modulation technique to reject noise in the reflectivity signal, and a stabilization scheme to lock the pump-probe frequency difference to a radio frequency reference (mutual coherence of 2.0 MHz in 30 s). These effects point to the presence of very slow fluctuations in the frequency separation of the hole spin ground states

In terms of

We have characterized the eigenenergies as a function of

EhZ implies a dephasing time