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Autonomous Picosecond-Precision Synchronization in Measurement-Device-Independent Quantum Key Distribution

A. P. Pljonkin

TL;DR

The paper addresses the critical need for picosecond-precision synchronization in MDI-QKD networks without extra channels or trusted clocks. It proposes an autonomous synchronization algorithm based on round-trip TOF measurements and Gaussian-noise statistical detection, suitable for fiber networks up to 100 km. The authors derive false-alarm probabilities, analyze detection reliability, and show via simulations that better than 10 ps timing accuracy is achievable, enhancing scalability of metropolitan and backbone quantum networks. This method reduces architectural complexity and enables practical deployment of MDI-QKD in real-world networks.

Abstract

Measurement-device-independent quantum key distribution (MDI-QKD) eliminates detector side-channel attacks by relocating all measurements to an untrusted intermediate node. However, its practical implementation critically relies on picosecond-level temporal synchronization between spatially separated users. In this work, we present a physically motivated autonomous synchronization algorithm for fiber-based MDI-QKD networks that does not require auxiliary optical channels or shared clock references. The method exploits round-trip optical pulse propagation and statistical signal detection in the presence of Gaussian noise. We derive analytical expressions for false-alarm probabilities, quantify detection reliability, and demonstrate through numerical modeling that synchronization accuracy better than 10~ps is achievable for channel lengths up to 100~km with realistic optical power levels. The proposed approach improves the scalability and robustness of MDI-QKD architectures and is directly applicable to metropolitan and backbone quantum networks.

Autonomous Picosecond-Precision Synchronization in Measurement-Device-Independent Quantum Key Distribution

TL;DR

The paper addresses the critical need for picosecond-precision synchronization in MDI-QKD networks without extra channels or trusted clocks. It proposes an autonomous synchronization algorithm based on round-trip TOF measurements and Gaussian-noise statistical detection, suitable for fiber networks up to 100 km. The authors derive false-alarm probabilities, analyze detection reliability, and show via simulations that better than 10 ps timing accuracy is achievable, enhancing scalability of metropolitan and backbone quantum networks. This method reduces architectural complexity and enables practical deployment of MDI-QKD in real-world networks.

Abstract

Measurement-device-independent quantum key distribution (MDI-QKD) eliminates detector side-channel attacks by relocating all measurements to an untrusted intermediate node. However, its practical implementation critically relies on picosecond-level temporal synchronization between spatially separated users. In this work, we present a physically motivated autonomous synchronization algorithm for fiber-based MDI-QKD networks that does not require auxiliary optical channels or shared clock references. The method exploits round-trip optical pulse propagation and statistical signal detection in the presence of Gaussian noise. We derive analytical expressions for false-alarm probabilities, quantify detection reliability, and demonstrate through numerical modeling that synchronization accuracy better than 10~ps is achievable for channel lengths up to 100~km with realistic optical power levels. The proposed approach improves the scalability and robustness of MDI-QKD architectures and is directly applicable to metropolitan and backbone quantum networks.

Paper Structure

This paper contains 6 sections, 4 equations, 7 figures.

Table of Contents

  1. Introduction
  2. MDI-QKD Synchronization Constraints
  3. Autonomous Synchronization Algorithm
  4. Statistical Detection Model
  5. Numerical Results
  6. Discussion and Conclusions

Figures (7)

  • Figure 1: Optical part of MDI-QKD scheme with polarization encoding.
  • Figure 2: Optical part of MDI-QKD scheme with phase encoding. LD --- radiation source; D --- photodetector; Coupler --- optical beam splitter; SPAD --- avalanche photodetectors; 50/50 --- X-type beam splitter; 95/5 --- Y-type beam splitter; FM --- mirror for reflecting optical signal; PBS --- polarizing beam splitter; Ci --- optical circulator; L --- optical arms; QC --- quantum communication channel; A --- Alice station; B --- Bob station; C --- Charlie station (untrusted node).
  • Figure 3: Synchronization process of stations in MDI-QKD configuration. Symbols + and – mean positive and negative condition (event) result.
  • Figure 4: Signal time window search
  • Figure 5: Optical signal desynchronization
  • ...and 2 more figures