Quantum Key Output Apparatus Photon Error Filtering
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Solution Overview
Problem
In quantum cryptographic key communication systems, the estimation of the upper limit of leakage information is affected by errors in the number of photons, leading to a decreased generation rate of quantum cryptographic keys due to conservative safety evaluations.
Innovation Solution
A quantum cryptographic key output apparatus that generates encoded pulsed laser light and branches it into two optical paths with a predetermined intensity ratio, allowing for the determination of photon errors and exclusion of photons with significant errors, thereby improving key generation rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the upper limit of leakage information is estimated conservatively to ensure security, then security is improved, but the generation rate of quantum cryptographic keys deteriorates
Solution Approach 1:
The patent applies preliminary action by measuring and recording the actual number of photons for each pulse before the key generation process. This allows the system to identify and exclude pulses with photon number errors in advance, rather than discarding keys after generation. By performing this filtering action preliminarily, the system maintains security through accurate photon number tracking while improving key generation rate by excluding only the necessary problematic pulses.
Solution Approach 2:
The patent changes the parameter tracking approach from assuming an average photon number to measuring and recording the actual photon number for each individual pulse. This parameter change enables more precise estimation of leakage information based on real measurements rather than conservative assumptions, allowing the system to maintain security while reducing unnecessary key discarding and improving generation rate.
2Reliability
If the error range of photon number is enlarged to ensure safety, then security is improved, but the amount of information to be reduced in confidentiality enhancement increases
Solution Approach 1:
The system performs preliminary measurement and recording of actual photon numbers for each pulse. This allows the confidentiality enhancement process to use accurate measured values rather than assuming enlarged error ranges, thereby maintaining safety while minimizing the amount of information that needs to be discarded.
Solution Approach 2:
The patent replaces the mechanical assumption-based error range estimation with actual measurement-based photon number tracking. By substituting the theoretical error range model with real measurement data, the system achieves accurate safety evaluation without unnecessarily enlarging error ranges, thus reducing information loss while maintaining security.
3Reliability
If conservative estimation is used for leakage information to guarantee safety, then security is improved, but the generation rate of quantum cryptographic keys deteriorates
Solution Approach 1:
The patent implements preliminary measurement and recording of actual photon numbers for each pulse before key generation. This allows the system to identify and exclude only the pulses with actual errors, rather than discarding keys based on conservative estimation. By performing this filtering action in advance with accurate data, the system guarantees safety while improving key generation rate.
Solution Approach 2:
The system replaces conservative estimation-based safety guarantee with actual measurement-based photon number tracking. This substitution eliminates the need for conservative over-estimation of leakage information, allowing the system to guarantee safety through accurate measurements while improving key generation rate by reducing unnecessary key discarding.
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
This approach enhances the generation rate of quantum cryptographic keys by accurately identifying and excluding photons with errors, thereby improving the system's security and efficiency.
Implementation Method 1
an optical branching unit that branches the encoded pulsed laser light to a first optical path and a second optical path at a predetermined light intensity ratio
Implementation Method 2
an attenuation unit that attenuates a light intensity of first pulsed laser light that is the pulsed laser light branched to the first optical path so that the number of photons of the first pulsed laser light has any one of a plurality of candidate values
Data Source
AI summary
A quantum cryptographic key output apparatus includes a semiconductor laser device that repeatedly generates pulsed laser light, an encoder that encodes the pulsed laser light based on a quantum cryptographic key, an optical branching unit that branches the pulsed laser light, and an attenuator that attenuates a light intensity of first pulsed laser light so that the number of photons of the first pulsed laser light has any one of a plurality of candidate values that are values equal to or smaller than 1. Further, the output apparatus includes a light intensity determination unit that determines whether or not a light intensity of a second pulsed laser light is in a predetermined range, and an information output unit that outputs specifying information for specifying the first pulsed laser light corresponding to second pulsed laser light of which the light intensity is not in the predetermined range to an input apparatus.