Light Protecting Device for Free Space Quantum Key Distribution
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Solution Overview
Problem
Current free space quantum key distribution systems face limitations in distance due to optical waveguide loss and are hindered by background noise, particularly direct light, which existing technologies inadequately address, especially at night and during the day.
Innovation Solution
A light protecting device is attached to the emitter to block direct light from beyond the emitter, acting as a physical barrier within the receiver's field of view, significantly reducing background noise and enhancing signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spatial, temporal and wavelength filtering are used to reduce background noise, then scattered light is reduced, but direct light from stars and planets remains and scattered light from ambient light always remains
Solution Approach 1:
The patent extracts and removes the direct light component from the background noise by using a physical barrier (light protecting device) that specifically blocks direct light paths from stars and planets behind the emitter, while allowing scattered light to pass through. This separates the treatment of different light components.
Solution Approach 2:
The light protecting device acts as an intermediary element positioned between the emitter and the receiver, physically blocking direct light paths from celestial bodies behind the emitter. This intermediary structure complements the existing filtering mechanisms by addressing the direct light component that filters cannot eliminate.
2Illumination intensity
If existing filtering technologies are applied, then scattered background light is reduced, but direct background light from stars and planets cannot be effectively removed
Solution Approach 1:
The patent segments the background noise reduction into two distinct components: scattered light reduction (handled by existing filters) and direct light reduction (handled by the light protecting device). This segmentation allows each component to be optimized independently.
Solution Approach 2:
The light protecting device provides localized protection by creating a specific geometric configuration (shielding structure) that blocks direct light paths from particular directions (behind the emitter), while maintaining transparency to other directions. This local quality approach targets specific noise sources without affecting the entire field of view.
3Measurement precision
If the receiver uses a predetermined field of view to receive data, then the receiver can detect the emitter, but direct light from beyond the emitter can enter the field of view and create noise
Solution Approach 1:
The light protecting device is positioned on the emitter to preemptively block direct light paths from celestial bodies before the light can reach the receiver's field of view. This preliminary action prevents the harmful light from entering the detection path in the first place.
Solution Approach 2:
The patent introduces a spatial dimension solution by placing a physical barrier in three-dimensional space around the emitter, rather than relying solely on spectral or temporal filtering. This geometric approach blocks direct light paths by occupying the physical space through which the light would travel.
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
The solution effectively minimizes direct background noise, improving signal quality and security against eavesdropping, applicable both day and night, by blocking unwanted light from entering the receiver's field of view.
Implementation Method 1
said light protecting device being configured to prevent any light coming from the environment beyond the emitter to enter within the field of view of said receiver
Data Source
AI summary
The present relates to a quantum communication system for free space quantum key distribution. An emitter and a receiver, the emitter and the receiver are two points distanced by a free space quantum communication channel, the emitter being designed for wirelessly transmitting data to the receiver via said free space optical communication channel. The receiver includes an optical device capable of receiving the data within a predetermined field of view extending from said optical device toward the receiver. The system is characterized in that the emitter further comprises a light protecting device attached on said emitter. The light protecting device is configured to prevent any light coming from the environment beyond the emitter to enter within the field of view of the receiver. The invention further relates to a method for optimizing free space quantum key distribution.