QKD Coincidence Window Tuning for Key Rate and QBER Balance
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Solution Overview
Problem
Conventional Quantum Key Distribution (QKD) protocols often limit the scope of offering maximal key rate against minimal Quantum-Bit-Error-Rate (QBER) by fixing a pre-agreed coincidence window span without optimization.
Innovation Solution
A method and system that dynamically determine the coincidence window span by iteratively adjusting reference lines in incremental steps to optimize performance parameters such as signal value, noise value, and QBER, using a computing system to extract and analyze coincidence distribution sets from detector pairs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fixed pre-agreed coincidence window span is used, then the protocol implementation is simple, but the key rate is limited and QBER cannot be minimized
Solution Approach 1:
The patent transforms the fixed coincidence window into a dynamic, adaptive parameter. The system iteratively adjusts the coincidence window span based on real-time analysis of coincidence distributions, allowing the window to expand or contract to optimize key rate while maintaining acceptable QBER. This dynamic adjustment resolves the contradiction by making the protocol adaptable rather than static.
Solution Approach 2:
The patent systematically varies the coincidence window span parameter during protocol execution. By testing multiple window spans and selecting the optimal one based on performance metrics (key rate and QBER), the system achieves higher productivity without requiring fundamentally new protocol mechanisms, thus managing complexity through parameter optimization rather than structural complexity.
2Productivity
If the coincidence window span is increased to capture more signals, then the key rate increases, but noise also increases reducing SNR
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors both signal coincidences and noise coincidences within the coincidence window. Based on this feedback, the system iteratively adjusts the window span to find the optimal balance point where key rate is maximized while QBER remains below the threshold for secure key generation. This feedback loop resolves the contradiction by dynamically balancing signal capture against noise rejection.
Solution Approach 2:
The patent employs a trial-and-error approach where the system tests coincidence window spans that may initially exceed the optimal value, capturing excessive noise, then iteratively refines the window size downward. This partial/excessive action strategy allows the system to explore the parameter space and converge on the optimal window span that achieves sufficient key rate without excessive noise, resolving the contradiction through iterative optimization.
3Reliability
If the coincidence window span is decreased to reduce noise, then QBER decreases, but the key rate is reduced due to fewer captured signals
Solution Approach 1:
The patent makes the coincidence window span a dynamic parameter that adapts to the specific experimental conditions and channel characteristics. Rather than using a fixed small window that limits key rate, the system dynamically determines the optimal window size based on real-time analysis of coincidence distributions, ensuring both low QBER and high key rate are achieved simultaneously through adaptive optimization.
4Productivity
If iterative adjustment of reference lines is performed to optimize time window, then performance is maximized, but computational time increases
Solution Approach 1:
The patent performs preliminary analysis of coincidence distributions to establish initial reference lines and coincidence window spans before actual key generation. By pre-processing the data to identify optimal parameters, the system reduces the computational burden during real-time operation while still achieving optimized performance. This preliminary action resolves the contradiction by separating the computationally intensive optimization phase from the time-sensitive key generation phase.
Data Source
AI summary
The present disclosure relates to field of quantum cryptography that discloses method of optimizing performance of Quantum Key Distribution (QKD) protocol. Computing system (101) extracts one or more coincidence distribution sets generated from one or more timestamps detected during communication by one or more detector pairs associated with sender and receiver of communication. Further, computing system identifies one or more reference lines indicating signal value and noise value in each of one or more coincidence distribution sets. Thereafter, computing system determines time window in one or more coincidence distribution sets by iteratively adjusting one or more reference lines in incremental steps until at least one of, performance parameters, signal value and noise value within time window complies with predefined requirements. Finally, computing system optimizes performance of QKD protocol based on determined time window. present disclosure provides an advantage of optimizing individual Signal-to-Noise Ratio (SNR) while restricting QBER to predefined limit.