Tunable and low-noise WSe$_2$ quantum emitters for quantum photonics

TL;DR

This study demonstrates that encapsulating WSe$_2$ quantum emitters in hBN and applying electrostatic bias significantly reduces spectral noise and linewidths, advancing the development of stable, tunable, and high-purity single-photon sources for quantum photonics.

Contribution

The paper introduces a systematic approach combining hBN encapsulation and electrostatic biasing to suppress noise and tune WSe$_2$ quantum emitters, achieving near transform-limited emission.

Findings

Spectral wandering reduced from ~170 μeV to ~40 μeV.

Linewidth narrowed from ~500 μeV to ~100 μeV.

High single-photon purity with g^{(2)}(0) ≈ 0.01.

Abstract

Low-noise and tunable single-photon sources are essential components of photonic quantum technologies. However, in WSe$_2$ quantum emitters, charge noise from fluctuations in their local electrostatic environment remains a major obstacle to achieving transform-limited single-photon emission and high photon indistinguishability. Here, we systematically investigate two noise mitigation strategies in hexagonal boron nitride (hBN) encapsulation and electrostatic biasing. We demonstrate that hBN encapsulation alone suppresses spectral wandering (from $\sim$170 $\mu$eV to $\sim$40 $\mu$eV) and narrows emission linewidths (from $\sim$500 $\mu$eV to $\sim$150 $\mu$eV), while applied bias enables stable Stark tuning over a 280 $\mu$eV range and further linewidth narrowing down to $\sim$100 $\mu$eV reaching the resolution-limited regime. Time-resolved and second-order correlation measurements confirm stable mono-exponential decay and high single-photon purity ($g^{(2)}(0) \approx 0.01$) with no observable blinking. To quantify progress toward the transform limit, we define two figures of merit: the linewidth ratio $R = W_{\text{exp}} / W_{\text{rad}}$ and total broadening $\Delta W = W_{\text{exp}} - W_{\text{rad}}$, with both being reduced more than five-fold in optimized devices. These results provide a robust framework for developing and evaluating low-noise, tunable WSe$_2$ quantum emitters, potentially realizing electrically controllable sources of indistinguishable single-photons for future photonic quantum technologies.