Generation of Coherent Quantum Light from a Single Impurity-Bound Exciton

TL;DR

This paper demonstrates coherent resonant optical emission from a single impurity-bound exciton in ZnSe, enabling phase-preserving quantum light generation and charge stabilization, advancing solid-state quantum emitter control.

Contribution

It is the first to show resonant excitation of impurity-bound excitons in II-VI semiconductors, enabling coherent quantum light emission and charge stabilization techniques.

Findings

High Debye-Waller factor of 0.94 indicating efficient zero-phonon line emission.

Identification of fast Auger recombination and slow charge tunneling processes.

Charge stabilization achieved with low-power laser pumping on nanosecond timescales.

Abstract

Impurity-bound excitons in II-VI direct-bandgap semiconductors are promising optically active solid-state spin qubits that combine exceptional optical quantum efficiency with an ultra-low spin noise environment. Previous studies on single impurities relied on incoherent optical excitation to generate photons. However, many quantum applications require resonant driving of quantum emitters to precisely control optical transitions and maintain coherence of the emission. Here, we demonstrate coherent optical emission of quantum light from a resonantly driven single impurity-bound exciton in ZnSe. The resonantly driven emitter exhibits bright quantum light emission that preserves the phase of the resonant drive, validated through polarization interferometry. Resonant excitation enables us to directly measure the Debye-Waller factor, determined to be 0.94, which indicates high efficiency emission to the zero-phonon line. Time-resolved resonance fluorescence measurements reveal a fast optically-driven ionization process that we attribute to Auger recombination, along with a slower spontaneous ionization process having a lifetime of 21 {\mu}s due to charge tunneling from the impurity. We show that incoherent, low-power laser pumping efficiently stabilizes the charge of the impurity-bound exciton on the timescale of 9.3 ns, recovering the resonance fluorescence emission from the bound exciton. These results pave the way for coherent optical and spin control of the single impurity states through resonant excitation of impurity-bound excitons in II-VI semiconductors.