Quantum Random Bit Generator Using Incompatible Observables
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Solution Overview
Problem
Current quantum random number generators do not adequately consider information loss due to impurity of the measured state and classical or quantum correlations, which can lead to predictability of generated numbers, especially when the quantum state is not pure or is controlled by a third party.
Innovation Solution
Measuring two incompatible observables of an electromagnetic field, such as time and position or phase and amplitude, to generate raw random numbers and estimate conditional min-entropy, using a randomness extractor algorithm calibrated on this entropy to produce a shorter sequence of truly random bits independent of quantum correlations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a randomness extractor algorithm is applied to eliminate classical noise, then the uniformity and independence of random bits are improved, but the length of the random bit sequence is reduced
Solution Approach 1:
The patent changes the parameter being measured from a single observable to two incompatible observables of the quantum system. By measuring both observables and using their joint statistical properties, the system maintains higher entropy extraction efficiency while improving the quality of random bits through the incompatibility relationship between the two measurements.
2Device complexity
If quantum systems with impure states or third-party control are used, then device complexity is reduced, but the predictability of generated numbers increases
Solution Approach 1:
The patent implements a feedback mechanism where the measurement results of the first observable are used to estimate the conditional min-entropy, which then determines the parameters for the randomness extractor algorithm. This adaptive feedback allows the system to compensate for state impurity and maintain security even when the quantum state is not perfectly pure or is partially controlled by a third party.
Solution Approach 2:
The patent replaces the requirement for perfect quantum state purity with a mathematical estimation approach based on conditional min-entropy. Instead of relying on the physical perfection of the quantum state, the system uses statistical estimation from measurement data to guarantee randomness, substituting a mechanical/purity requirement with an information-theoretic approach.
3Measurement precision
If two incompatible observables are measured, then the estimate of conditional min-entropy is improved, but the measurement time and system complexity increase
Solution Approach 1:
The patent performs preliminary measurements of the first observable to estimate the conditional min-entropy before finalizing the random bit generation process. These preliminary measurements provide the statistical basis for determining the security parameters, allowing the system to efficiently generate random bits without requiring extensive additional measurements for entropy estimation.
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 reduces classical noise and non-casual bits that can be predicted by adversaries, resulting in a higher degree of randomness and security of generated numbers, even when the quantum state is impure or correlated with other systems.
Implementation Method 1
a homodyne receiver (10) configured to receive an electromagnetic signal (101) in a quantum state and to provide measurement results of two continuous observables of the electromagnetic signal
Data Source
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AI summary
The invention is a random number generator (1, 1000) that includes means (10, 10a, 10b) to measure two continuous observables of an electromagnetic field (101) prepared in a quantum state, and conversion means (106) to obtain, by the measure of each observable, a first and a second sequence of bits. A processing unit (113) calculates the conditional min-entropy of the random variable associated with the first sequence. A unit of post-processing (108) extracts a third sequence of random bits whose length depends on the conditional min-entropy of the first sequence. The output of the post-processing unit (108) is therefore a set of random bits that can be inserted in a data signal, such as a signal that carries a cryptographic key. The invention is also related to a method for generating random numbers.