Tunable and Low-Noise WSe 2 Quantum Emitters for Quantum Photonics

Low-noise and tunable single-photon sources are essential components of photonic quantum technologies. However, in <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msub> <a:mi>WSe</a:mi> <a:mn>2</a:mn> </a:msub> </a:math> 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 ( <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi>h</c:mi> </c:math> - <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mi>BN</e:mi> </e:math> ): encapsulation and electrostatic biasing. We demonstrate that <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mi>h</g:mi> </g:math> - <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:mi>BN</i:mi> </i:math> encapsulation alone suppresses spectral wandering (from <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"> <k:mo>∼</k:mo> <k:mn>170</k:mn> <k:mspace width="0.1em"/> <k:mtext fontfamily="times">μ</k:mtext> <k:mi>eV</k:mi> </k:math> to <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"> <o:mo>∼</o:mo> <o:mn>40</o:mn> <o:mspace width="0.1em"/> <o:mtext fontfamily="times">μ</o:mtext> <o:mi>eV</o:mi> </o:math> ) and narrows emission linewidths (from <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"> <s:mo>∼</s:mo> <s:mn>524</s:mn> <s:mspace width="0.1em"/> <s:mtext fontfamily="times">μ</s:mtext> <s:mi>eV</s:mi> </s:math> to <w:math xmlns:w="http://www.w3.org/1998/Math/MathML" display="inline"> <w:mo>∼</w:mo> <w:mn>120</w:mn> <w:mspace width="0.1em"/> <w:mtext fontfamily="times">μ</w:mtext> <w:mi>eV</w:mi> </w:math> ), while applied bias enables stable Stark tuning over a <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" display="inline"> <ab:mn>280</ab:mn> <ab:mspace width="0.1em"/> <ab:mtext fontfamily="times">μ</ab:mtext> <ab:mi>eV</ab:mi> </ab:math> range and further linewidth narrowing down to <eb:math xmlns:eb="http://www.w3.org/1998/Math/MathML" display="inline"> <eb:mo>∼</eb:mo> <eb:mn>100</eb:mn> <eb:mspace width="0.1em"/> <eb:mtext fontfamily="times">μ</eb:mtext> <eb:mi>eV</eb:mi> </eb:math> , reaching the resolution-limited regime. Time-resolved and second-order correlation measurements confirm stable monoexponential decay and high single-photon purity [ <ib:math xmlns:ib="http://www.w3.org/1998/Math/MathML" display="inline"> <ib:msup> <ib:mi>g</ib:mi> <ib:mrow> <ib:mo stretchy="false">(</ib:mo> <ib:mn>2</ib:mn> <ib:mo stretchy="false">)</ib:mo> </ib:mrow> </ib:msup> <ib:mo stretchy="false">(</ib:mo> <ib:mn>0</ib:mn> <ib:mo stretchy="false">)</ib:mo> <ib:mo>∼</ib:mo> <ib:mn>0.01</ib:mn> </ib:math> ] with no observable blinking. To quantify progress toward the transform limit, we define two figures of merit—the linewidth ratio <ob:math xmlns:ob="http://www.w3.org/1998/Math/MathML" display="inline"> <ob:mi>R</ob:mi> <ob:mo>=</ob:mo> <ob:msub> <ob:mi>W</ob:mi> <ob:mi>exp</ob:mi> </ob:msub> <ob:mo>/</ob:mo> <ob:msub> <ob:mi>W</ob:mi> <ob:mi>dec</ob:mi> </ob:msub> </ob:math> and total broadening <qb:math xmlns:qb="http://www.w3.org/1998/Math/MathML" display="inline"> <qb:mi mathvariant="normal">Δ</qb:mi> <qb:mi>W</qb:mi> <qb:mo>=</qb:mo> <qb:msub> <qb:mi>W</qb:mi> <qb:mi>exp</qb:mi> </qb:msub> <qb:mo>−</qb:mo> <qb:msub> <qb:mi>W</qb:mi> <qb:mi>dec</qb:mi> </qb:msub> </qb:math> —with both being reduced more than fivefold in optimized devices. These results provide a robust framework for developing and evaluating low-noise, tunable <tb:math xmlns:tb="http://www.w3.org/1998/Math/MathML" display="inline"> <tb:msub> <tb:mi>WSe</tb:mi> <tb:mn>2</tb:mn> </tb:msub> </tb:math> quantum emitters, potentially realizing electrically controllable sources of indistinguishable single photons for future photonic quantum technologies.