Telecom Networking with a Diamond Quantum Memory

Abstract

Practical quantum networks require interfacing quantum memories with existing channels and systems that operate in the telecom band. Here we demonstrate low-noise, bidirectional quantum frequency conversion that enables a solid-state quantum memory to directly interface with telecom-band systems. In particular, we demonstrate conversion of visible-band single photons emitted from a silicon-vacancy (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mi>Si</a:mi></a:math><d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><d:mi>V</d:mi></d:math>) center in diamond to the telecom <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><g:mrow><g:mrow><g:mi mathvariant="normal">O</g:mi></g:mrow></g:mrow></g:math> band, maintaining low noise (<k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><k:msup><k:mi>g</k:mi><k:mn>2</k:mn></k:msup><k:mo stretchy="false">(</k:mo><k:mn>0</k:mn><k:mo stretchy="false">)</k:mo><k:mo>&lt;</k:mo><k:mn>0.1</k:mn></k:math>) and high indistinguishability (<p:math xmlns:p="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><p:mi>V</p:mi><p:mo>=</p:mo><p:mn>89</p:mn><p:mo>±</p:mo><p:mn>8</p:mn><p:mi mathvariant="normal">%</p:mi></p:math>). We further demonstrate the utility of this system for quantum networking by converting telecom-band time-bin pulses, sent across a lossy and noisy 50-km deployed fiber link, to the visible band and entangling them with a diamond quantum memory with fidelity <t:math xmlns:t="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><t:mrow><t:mi mathvariant="script">F</t:mi></t:mrow><t:mo>≥</t:mo><t:mn>87</t:mn><t:mo>±</t:mo><t:mn>2.5</t:mn><t:mi mathvariant="normal">%</t:mi></t:math>. These results demonstrate the viability of <y:math xmlns:y="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><y:mi>Si</y:mi></y:math><bb:math xmlns:bb="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><bb:mi>V</bb:mi></bb:math> quantum memories integrated with telecom-band systems for scalable quantum networking applications. Published by the American Physical Society 2024