Quantum Key Distribution Intensity Modulation Pattern Filtering

Solution Overview

Problem

The decoy method in quantum key distribution systems experiences efficiency degradation due to intensity fluctuations and the pattern effect, leading to increased information leakage and reduced encryption key generation efficiency, especially when decoy pulse intensity fluctuates by 5% and the pattern effect causes waveform distortion.

Innovation Solution

A quantum key distribution system employing a transmitting device with an encoding unit, an intensity modulating unit that applies N types of intensity modulation with different timings, and key distillation processing units to generate encryption keys by removing data from specific modulation patterns, where N is an integer greater than or equal to three, thereby mitigating the effects of intensity fluctuations and pattern effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the decoy method is used to detect eavesdropping by changing optical pulse intensities, then the safety of quantum key distribution is improved, but the generation efficiency of encryption keys significantly degrades due to intensity fluctuations and pattern effects

Engineering Contradiction:

Improvesafety of quantum key distributionVSAvoidgeneration efficiency of encryption keys

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent extracts and removes data obtained from optical pulses with specific modulation patterns (particularly decoy pulses affected by pattern effects) from the data sequence used for encryption key generation. This selective extraction eliminates the harmful influence of intensity fluctuations while preserving the integrity of the key generation process, thereby maintaining safety without the significant efficiency degradation that would result from using all decoy data.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the parameter selection criteria by introducing a specific modulation pattern as a filtering condition. Instead of using all optical pulse data uniformly, the system selectively processes data based on modulation pattern characteristics, removing data from pulses with patterns susceptible to intensity fluctuations. This parameter-based selection resolves the contradiction by maintaining the security benefits of the decoy method while eliminating efficiency-reducing factors.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If data from all optical pulses including decoy pulses are used for encryption key generation, then the productivity is improved, but the reliability degrades due to information leakage from intensity fluctuations

Engineering Contradiction:

Improvegeneration efficiency of encryption keysVSAvoidsafety of quantum key distribution

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent extracts and removes data obtained from optical pulses with specific modulation patterns (particularly decoy pulses affected by pattern effects) from the data sequence used for encryption key generation. This selective extraction eliminates the harmful influence of intensity fluctuations while preserving the integrity of the key generation process, thereby maintaining safety without the significant efficiency degradation that would result from using all decoy data.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies different processing quality standards to different portions of the data sequence based on their modulation patterns. Data from pulses with specific patterns (decoy pulses susceptible to pattern effects) are removed or treated differently, while data from other pulses are used normally. This local differentiation ensures that only reliable data contribute to key generation, maintaining both security and efficiency.

Inventive Principle:

Principle #3Local quality

3Device complexity

If the pattern effect is not compensated, then the device complexity is reduced, but the manufacturing precision of optical pulse intensities deteriorates

Engineering Contradiction:

Improvecomplexity of intensity modulation systemVSAvoidprecision of optical pulse intensity modulation

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent extracts and removes data obtained from optical pulses with specific modulation patterns (particularly decoy pulses affected by pattern effects) from the data sequence used for encryption key generation. This selective extraction eliminates the harmful influence of intensity fluctuations while preserving the integrity of the key generation process, thereby maintaining safety without the significant efficiency degradation that would result from using all decoy data.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS11502831B2Transmitting device, receiving device, quantum key distribution method, and quantum key distribution program for quantum key distribution system

Publication Date: 2022.11.15 NEC CORP

AI summary

A quantum key distribution device is provided with an encoding unit which encodes an optical pulse train; an intensity modulating unit which subjects the encoded optical pulse train to N (where N is an integer at least equal to 3) types of intensity modulation having mutually different intensities, with different timings; and a first key distillation processing unit which generates an encryption key on the basis of a data sequence obtained by removing data obtained from an optical pulse having a specific modulation pattern from a data sequence used by the encoding unit and the intensity modulating unit.