CV-QKD Passive Beam Splitter Multi-User Key Distribution
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Solution Overview
Problem
Existing quantum key distribution (QKD) systems face challenges in efficiently sharing a secret key between a transmitter and multiple receivers, particularly in continuous-variable (CV-QKD) systems, due to the imbalance in component costs and the need for complex active switching or wavelength-division multiplexing, which limits simultaneous data transmission and synchronization.
Innovation Solution
A CV-QKD system utilizing a passive beam splitter to split a modulated quantum signal into multiple sub-signals, allowing each receiver to determine phase space positions and generate an individual secret key through a reverse reconciliation process, with synchronization signals maintained via a passive optical network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If active switching is used to connect multiple receivers to a single transmitter, then individual secret keys can be shared between transmitter and receivers, but the system complexity increases and simultaneous data transmission is prevented
Solution Approach 1:
The quantum channel is segmented into multiple independent optical paths using a passive optical splitter, allowing each receiver to have its own dedicated quantum channel from the transmitter without requiring active switching between users
Solution Approach 2:
The passive optical splitter serves multiple receivers simultaneously with a single quantum channel, making the system universal for multi-user quantum key distribution without requiring user-specific switching mechanisms
2Quantity of substance
If wavelength-division multiplexing is used to increase bandwidth for multiple users, then more users can connect, but the system becomes rigid and wavelength selection cannot be modified without changing optical components
Solution Approach 1:
Instead of using multiple wavelengths to serve multiple users (WDM), the invention inverts the approach by using a single wavelength that is split into multiple spatial paths, allowing flexible user allocation without wavelength changes
3Ease of operation
If the quantum channel is completely severed during active switching, then users can be connected sequentially, but control signals for alignment cannot be transmitted and long recalibration time is needed
Solution Approach 1:
The passive optical splitter maintains continuous quantum channel connectivity to all receivers simultaneously, allowing control signals and alignment information to be transmitted continuously without interruption or recalibration when users are connected or disconnected
4Reliability
If independent QKD links are set up between transmitter and each receiver, then individual secret keys can be shared, but the setup becomes complicated and resource intensive
Solution Approach 1:
Multiple independent QKD links are merged into a single quantum channel that is split using a passive optical splitter, allowing individual secret keys to be generated with each receiver while simplifying the overall system configuration and reducing resource requirements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables secure, efficient sharing of individual secret keys between a transmitter and multiple receivers using passive optical switching, reducing costs and maintaining synchronization, while allowing simultaneous data transmission.
Implementation Method 1
a beam splitter configured to split the modulated quantum signal into a plurality of modulated quantum sub-signals
Data Source
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AI summary
The invention relates to a continuous variable quantum key distribution, CV-QKD, system (100), comprising: a transmitter (101) comprising a modulator (103) configured to modulate a quantum signal according to a continuous or discrete distribution in phase and amplitude; a beam splitter (111) configured to split the modulated quantum signal into a plurality of modulated quantum sub-signals; and a plurality of receivers (121-1, 121-2, 121-N), wherein each receiver is configured to: receive via a respective quantum communication channel a respective modulated quantum sub-signal from the beam splitter (111); determine a plurality of phase space positions defined by a plurality of quadrature components of the respective modulated quantum sub-signal; and determine an individual secret key on the basis of the plurality of phase space positions by carrying out a post-processing procedure, the post-processing procedure comprising a reverse reconciliation procedure.