Quantum Key Distribution Transmitter Spatial Filtering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Quantum key distribution systems using free-space optical communication are vulnerable to attacks based on spatially and amplitude distinguishable photon states, which compromise the security of encryption keys.
Innovation Solution
An optical transmitter system that combines light signals from multiple sources with unique encodings and filters them through a spatial filter with an aperture diameter less than or equal to the wavelength, ensuring the output light signals are spatially and amplitude indistinguishable, preventing eavesdropping attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple light sources are used with unique encodings, then the encoding capacity is improved, but the signals become spatially distinguishable making them vulnerable to attacks
Solution Approach 1:
A spatial filter with aperture diameter less than or equal to the wavelength is introduced as an intermediary component between the beam combiner and the transmission medium. This spatial filter acts as a mediator that processes the combined light signals from multiple sources, rendering them spatially indistinguishable while preserving their encoding information, thus preventing eavesdropping attacks based on spatial distinguishability
Solution Approach 2:
The patent changes the critical parameter of aperture diameter to be less than or equal to the wavelength of light. This parameter change transforms the spatial filter's effect on the light signals, causing them to become spatially indistinguishable when emerging from the filter, thereby eliminating the vulnerability to spatial-based attacks while maintaining encoding capacity
2Object-affected harmful factors
If a spatial filter with aperture diameter less than or equal to wavelength is used, then spatial indistinguishability is improved, but the system complexity increases
Solution Approach 1:
The patent combines multiple light sources and their optical paths into a single integrated system using a beam combiner. This merging approach allows all sources to be processed through a single spatial filter with the critical aperture diameter parameter, simplifying the overall system architecture compared to having separate filtering mechanisms for each source
3Manufacturing precision
If precise alignment of optical components is performed, then the manufacturing precision is improved, but the ease of manufacture deteriorates
Solution Approach 1:
By changing the aperture diameter parameter to be less than or equal to the wavelength, the spatial filter inherently enforces spatial indistinguishability without requiring precise alignment of multiple optical components. This parameter change reduces the manufacturing complexity and alignment requirements compared to systems that would need complex optical benches and precision mounting
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 system effectively prevents side-channel attacks by making the encoded light signals spatially and amplitude indistinguishable, thereby maintaining the security of the encryption keys during quantum key distribution.
Implementation Method 1
The spatial filter has an aperture with a diameter that is less than or equal to the wavelength of the light signals from the light sources. The spatial filter can output a filtered light signal where the signal components (e.g. the individual light pulses) corresponding to each light source are spatially indistinguishable.
Data Source
AI summary
An optical transmitter for quantum key distribution includes a plurality of spatially separated light sources configured to emit a light signal with the same wavelength. Each light source emits a light signal with a unique encoding. A beam combiner receives the light signals from the plurality of light sources and combines the received light signals into a combined light signal. A spatial filter is optically coupled to the beam combiner and includes an aperture that receives the combined light signal and emits a filtered light signal. The aperture has an aperture diameter less than or equal to the specified wavelength. A collimator is optically coupled to the spatial filter and receives the filtered light signal and emits a collimated light signal. An output aperture receives the collimated light signal and outputs the collimated light signal as an output light signal towards an optical receiver.