Fast single-photon detectors and real-time key distillation enable high secret-key-rate quantum key distribution systems

Abstract

Quantum key distribution has emerged as the most viable scheme to guarantee information security in the presence of large-scale quantum computers and, thanks to the continuous progress made in the past 20 years, it is now commercially available. However, the secret key rates remain limited to just over 10 Mbps due to several bottlenecks on the receiver side. Here we present a custom multipixel superconducting nanowire single-photon detector that is designed to guarantee high count rates and precise timing discrimination. Leveraging the performance of the detector and coupling it to fast acquisition and real-time key distillation electronics, we remove two major roadblocks and achieve a considerable increase of the secret key rates with respect to the state of the art. In combination with a simple 2.5-GHz clocked time-bin quantum key distribution system, we can generate secret keys at a rate of 64 Mbps over a distance of 10.0 km and at a rate of 3.0 Mbps over a distance of 102.4 km with real-time key distillation.

Advantages of Asynchronous Measurement-Device-Independent Quantum Key Distribution in Intercity Networks

“…Quantum key distribution (QKD) [1,2] enables remote two parties to share secret keys protected from eavesdropping by the laws of physics. In the past forty years, QKD has achieved rapid development in terms of secret key rates [3][4][5][6], transmission distance [7][8][9] and network deployment [10][11][12][13]. Although the security of QKD has been proven in theory, the imperfections of realistic devices lead to various security loopholes [14][15][16], especially in detection [15].…”

“…The secret key rates of the three-intensity asynchronous MDI-QKD protocol with click filtering. Here the fiber loss is 0.16 dB/km; the clock rate is 4 GHz; the dark count rates is 0.1 Hz; and the detection efficiency is η d = 80% 6…”

Gigahertz Detection Rates and Dynamic Photon-Number Resolution with Superconducting Nanowire Arrays

“…Such photons can be used in LOQC, GBS, , and quantum repeater protocols for long distance communication, , which generally require very narrow bandwidth photons to match those of quantum memories. Independent multipixel SNSPD arrays have been investigated to remove the limitations of series and parallel designs in terms of maximum detection rate, at the cost of a more complex readout. − However, a full analysis of the PNR capabilities of independent multipixel arrays and a demonstration of operation with long light pulses are crucially still lacking.…”

“…These capabilities open up new prospects for singlephoton applications, such as QKD, that require the highestefficiency detection at increased detection rates. 38 In fact, a similar device, which we fabricated and characterized, has already been exploited to demonstrate high-speed QKD, with secret-key rates exceeding 60 Mbps over a distance of 10 km. 38 We investigate in depth the dynamic PNR capabilities of the array and demonstrate accurate state reconstruction for different photon-number statistics for a wide range of light inputs, imitating operation with photons with long coherence times, as is of interest for LOQC, GBS, and quantum repeater protocols.…”

“…38 In fact, a similar device, which we fabricated and characterized, has already been exploited to demonstrate high-speed QKD, with secret-key rates exceeding 60 Mbps over a distance of 10 km. 38 We investigate in depth the dynamic PNR capabilities of the array and demonstrate accurate state reconstruction for different photon-number statistics for a wide range of light inputs, imitating operation with photons with long coherence times, as is of interest for LOQC, GBS, and quantum repeater protocols. We show a two-photon fidelity of 74% and a threephoton fidelity of 57%, which represent state-of-the-art results for fiber-coupled SNSPDs.…”