High-Rate Measurement-Device-Independent Quantum Communication without Optical Reference Light

In the realm of long-distance quantum communication, asynchronous measurement-device-independent quantum key distribution (AMDI-QKD) stands out for its experimental simplicity and high key rate generation. Despite these advantages, there exists a challenge in finding a balance between simplifying the laser system further and achieving high key rates. To address this challenge, we have devised a postmeasurement compensation scheme to accurately estimate the mutual frequency offset between two compact lasers using just the announced quantum-signal detection results, thereby obviating the need for optical reference light. As a result, we demonstrate an AMDI-QKD system operating at 2.5 GHz and achieving secure key rates (SKRs) of 537 and <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mn>101</a:mn><a:mtext> </a:mtext><a:mtext> </a:mtext><a:mi>kbit</a:mi><a:mo>/</a:mo><a:mi mathvariant="normal">s</a:mi></a:mrow></a:math> at distances of 100 and 201 km, respectively, showcasing a significant key rate improvement compared to similar setups. By leveraging ultrastable lasers, we achieve the highest SKRs with measurement-device-independent security within the 100–400-km range. Over 100 km, we reach a remarkable key rate of <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"><d:mrow><d:mn>1.03</d:mn><d:mtext> </d:mtext><d:mtext> </d:mtext><d:mi>Mbit</d:mi><d:mo>/</d:mo><d:mi mathvariant="normal">s</d:mi></d:mrow></d:math>, which could enable real-time one-time-pad video encryption. These findings render AMDI-QKD as a promising contender for the establishment of high performance and cost-effective large-scale intercity quantum networks.