Quantum Random Number Generator Entropy Scaling via Temporal Mode Encoding
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Solution Overview
Problem
Current quantum random number generators face challenges in achieving high bitrates and security while maintaining cost-effectiveness and versatility, often requiring complex and costly components, leading to limitations in industrial applications.
Innovation Solution
The method involves using a cascade of fiber-based beam splitters to create multiple temporal and spatial states, allowing for entropy scaling without changing the source or detector properties, by dividing single photons into paths and recombining them, and encoding photon arrival times into physical and virtual time-bins, thereby increasing the dimensionality of the state space and randomness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the dimensionality of measurement bases is increased using temporal mode encoding, then the random bitrate is improved, but the detector dead time and jitter limitations are exacerbated
Solution Approach 1:
The patent transitions from spatial mode encoding to temporal mode encoding, utilizing the time dimension to create multiple measurement bases. By encoding quantum states in temporal modes with different arrival times, the system achieves higher dimensionality (I=2^n states with n beam splitters) without requiring additional spatial channels or detectors, thereby avoiding the dead time and jitter limitations of detectors.
Solution Approach 2:
The patent introduces dynamic temporal binning where the detection window is divided into multiple time bins that can be adjusted in number and duration. This dynamic temporal resolution allows the system to adapt the measurement basis dimensionality by changing the number of time bins, enabling flexible control over the random bitrate without being constrained by fixed detector characteristics.
2Productivity
If multiple spatial modes are used to increase state space, then the dependency on expensive sources and high-performance detectors is reduced, but the design complexity increases due to requiring a single photon detector for each spatial mode
Solution Approach 1:
The patent makes a single detector universal by using temporal mode multiplexing. The same detector can measure multiple temporal modes sequentially within a detection window, effectively performing the function of multiple spatial mode detectors. The system processes I=2^n temporal states through a single detector by dividing the detection window into corresponding time bins, eliminating the need for multiple detectors while maintaining high state space dimensionality.
Solution Approach 2:
The patent replaces spatial dimensionality with temporal dimensionality. Instead of using multiple spatial modes that would require multiple detectors, the system uses temporal modes where photons arrive at different times within a detection window. This temporal encoding achieves the same state space expansion (Nv×I states) with a single detector, dramatically reducing device complexity.
3Reliability
If quantum random number generators are optimized on a case-by-case basis with specific sources and detectors, then performance is improved for that configuration, but versatility and tunability are reduced
Solution Approach 1:
The patent implements dynamic tunability by allowing the number of temporal bins (Nv) and the number of beam splitters (n) to be adjusted independently. This creates a flexible system where the state space dimensionality (Nv×I=Nv×2^n) and random bitrate can be tuned according to application requirements without changing the physical hardware configuration, achieving both optimization and versatility.
Solution Approach 2:
The patent creates a universal quantum random number generator platform that can adapt to different application requirements. The same core architecture with beam splitters and a single detector can be configured to produce different numbers of temporal states by adjusting the temporal binning parameters, making the system versatile across different applications while maintaining optimized performance through parameter tuning.
4Reliability
If self-testing quantum random number generators are used to achieve certified genuine randomness, then security is improved, but the random bit generation rate deteriorates
Solution Approach 1:
The patent uses high-dimensional temporal mode encoding to generate I=2^n distinguishable temporal states that can be certified as quantum random through violation of generalized Bell inequalities. The increased dimensionality provides stronger security certification while the temporal multiplexing allows efficient measurement of all states through a single detector, maintaining high random bit generation rates despite the enhanced security requirements.
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 random bit rate and security of quantum random number generators, achieving high performance with affordable components and minimal system complexity, allowing for tunable control over randomness and bit generation rate, making it suitable for commercial applications.
Implementation Method 1
dividing a source of single photons into two paths in a first beam splitter and recombining the two paths in a next beam splitter
Implementation Method 2
yielding a number I=2n of temporal states for each photon, where n is the number of beam splitters in the cascade
Implementation Method 3
detecting first temporal states by measuring a photon rate in a temporal window selected to measure photon arrival times
Data Source
AI summary
A method for entropy scaling in quantum random number generators, comprising dividing one spatial mode into multiple spatial modes, delaying each spatial mode, and recombing the spatial modes; detecting first temporal states with synchronisation to a photon generation time and encoding the first temporal states into first time bins; detecting second temporal states in an arbitrary clock, and encoding the second temporal states into second time-bins. The method comprises dividing a source of single photons into two paths in a first beam splitter and recombining the two paths in a next beam splitter, repeatedly, in a cascade of n beam splitters, consecutive beam splitters being separated by a length of fiber, yielding a number I=2n of temporal states for each photon; detecting first temporal states by measuring a photon rate in a temporal window selected to measure photon arrival times, with synchronisation to a generation time of the photons, and encoding the first temporal states into first time bins, a number of the first temporal states being I=2n; detecting second temporal states by measuring a photon rate in the selected temporal window, in absence of synchronisation to the generation time of the photon, and encoding the second temporal states into second time-bins, a number of the second time bins being Nv; thereby generating a state space for each photon of Nv×I.