Enhancement of Indistinguishable Photon Emission from a GaAs Quantum Dot via Charge Noise Suppression

TL;DR

This paper demonstrates a method to suppress charge noise in GaAs quantum dots, significantly improving photon indistinguishability and coherence times, which are crucial for quantum communication and computing applications.

Contribution

The study introduces a simple electrical control technique to reduce charge noise in GaAs quantum dots, enhancing photon coherence and emission quality without complex echo schemes.

Findings

Achieved a photon extraction efficiency of ~37%.

Maximum exciton dephasing time of ~6.8 ns, near the Fourier limit.

Visibility of two-photon interference reaches 97% at optimal bias.

Abstract

The generation of indistinguishable single photons is a fundamental requirement for future quantum technologies, particularly in quantum repeater networks and for distributed quantum computing based on entanglement distribution. However, spectral jitter, often induced by charge noise in epitaxial quantum dots, leads to exciton dephasing, thereby limiting their practical usage in quantum applications. We present a straightforward approach to mitigate charge noise-induced decoherence in droplet-etched GaAs quantum dots embedded in an n-i-p diode structure and integrated deterministically into an electrically contacted circular Bragg grating resonator for emission enhancement. The quantum device allows for the stabilization of the charge environment by applying an external electrical field while producing a photon extraction efficiency of approximately (37 +- 2)%. Hong-Ou-Mandel two-photon interference measurements reveal a strong voltage dependence of the exciton dephasing time and interference visibility on the applied bias in excellent agreement with our theoretical predictions. Notably, the reduction in visibility from a maximum, charge-stabilized corrected value of 97 percent at the optimum bias point follows an inverse square dependence (proportional to 1/I^2) with increasing diode current (I) in forward direction. Under a quasi-resonant excitation scheme, we achieve a maximum exciton dephasing time (T2*) of approximately (6.8 +-0.5) ns, reaching nearly the Fourier limit (T2 = 2T1) without the need for complex echo schemes like Ramsey or Carr-Purcell-Meiboom-Gill sequences. These findings are consistent with theoretical predictions from rate equation modeling and quantum optical analysis as well as voltage-dependent linewidth measurements, demonstrating optimized electrical control of exciton dephasing.