Quantum Random Number Generator Pulse Combining
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Solution Overview
Problem
Current Quantum Random Number Generators (QRNGs) based on gain-switched lasers face limitations in performance and speed due to the constraint that photodetectors can operate at a faster rate than pulsed lasers, restricting the maximum rate of phase randomization and random number generation.
Innovation Solution
The solution involves combining phase-randomized pulses from multiple gain-switched lasers to form a combined pulse sequence, allowing for higher rate generation and measurement of phase randomization using a time delay interferometer, while ensuring temporal offsets and synchronization of modulation currents to maintain random phase relationships between pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single gain-switched laser is used to generate phase-randomized pulses, then the device structure remains simple, but the random number generation rate is limited by the laser's pulse repetition rate
Solution Approach 1:
The system divides the pulse generation task across multiple gain-switched lasers, where each laser operates at a manageable repetition rate (e.g., 1-10 GHz) and generates phase-randomized pulses independently. These segmented pulse streams are then combined through optical interference to achieve an effective generation rate that is the sum of individual laser rates, thereby overcoming the single-laser rate limitation without requiring any single laser to operate at impractically high speeds
Solution Approach 2:
Multiple pulse streams from separate gain-switched lasers are merged through optical interference in a combiner. The interference of pulses with random phase relationships from different lasers creates a combined signal where the effective random number generation rate is enhanced. This merging process allows the system to achieve high generation rates while maintaining reasonable individual laser operating parameters
2Productivity
If the pulse repetition rate of gain-switched lasers is increased to improve random number generation speed, then the generation rate improves, but the lasers become difficult to operate at such high rates
Solution Approach 1:
The high generation rate requirement is segmented across multiple lasers operating at lower, more manageable repetition rates. Each laser operates within its optimal performance range (1-10 GHz) where it can be easily controlled and maintained, while the collective output of multiple lasers achieves the desired high effective generation rate. This segmentation eliminates the need to push individual lasers beyond their operational limits
Solution Approach 2:
The system transitions from a single-dimensional approach (one laser at high repetition rate) to a multi-dimensional approach (multiple lasers at lower repetition rates combined through optical interference). By adding the dimension of multiple parallel laser channels, the system achieves high effective generation rates while each individual laser operates in its comfortable performance regime, improving ease of operation
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 performance and speed of QRNGs by increasing the rate of random number generation beyond the limitations of individual pulsed lasers, achieving higher interference rates and improved randomness in generated numbers.
Implementation Method 1
the lasing threshold is governed by spontaneous emission, which is a quantum mechanical process, such that the phase of the emitted pulse is random
Implementation Method 2
a phase measurement element, the phase measurement element being configured to receive the combined stream of pulses
Data Source
AI summary
An optical device for a quantum random number generator comprising:a source of phase randomised pulses of light, the source of phase randomised pulses of light further comprisinga plurality of gain-switched lasers, each gain-switched laser having an output, and each gain-switched laser being configured to emit a stream of pulses such that the phase of each pulse in the stream of pulses is randomised, andan optical pulse combiner, the optical pulse combiner being configured to receive streams of pulses from the output of each gain-switched laser, combine the streams of pulses with one another into a combined stream of pulses and direct the combined stream of pulses into at least one output of the optical pulse combiner, the at least one output of the optical pulse combiner being the output of the source of phase randomised pulses of light;wherein the source of phase randomised pulses of light is configured such that the streams of pulses of light emitted by the plurality of gain-switched lasers are temporally offset relative to one another,a phase measurement element, the phase measurement element being configured to receive the combined stream of pulses from the output of the source of phase randomised pulses of light; andan optical detector, the optical detector being optically coupled to the phase measurement element.