Optical Quantum Random Number Generators With Pulse Amplification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional optical quantum random number generators (QRNGs) face issues such as small voltage pulses that do not optimally utilize the dynamic range of analog-to-digital converters (ADCs), initial pulse coherence reduction leading to classical noise, and contamination by electrical crosstalk, which degrade performance, especially at high repetition rates or in photonic integrated circuits.
Innovation Solution
The proposed QRNG employs an optical amplifier to enhance pulse intensity before interference, blocks or reduces the initial portion of pulses to minimize classical noise, and uses two photodetectors to suppress crosstalk by taking the difference between their outputs, thereby optimizing signal processing and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical amplifier is used to amplify pulse intensity, then the voltage pulse amplitude increases and ADC dynamic range utilization improves, but device complexity and noise may increase
Solution Approach 1:
An optical amplifier is introduced as an intermediary component between the laser source and the interference stage. This amplifier boosts the intensity of phase-randomized optical pulses before they undergo interference, ensuring that the resulting voltage pulses from photodetection have sufficient amplitude to optimally utilize the ADC's dynamic range without requiring excessive electronic amplification that would introduce classical noise.
2Reliability
If initial portion of pulse is blocked to reduce classical noise, then signal quality improves, but pulse energy is lost
Solution Approach 1:
The initial portion of each optical pulse, which contains reduced coherence and generates classical noise when interfered, is extracted and blocked using an optical switch or gate. This selective removal of the problematic pulse segment prevents it from contributing to the interference signal, thereby improving the quality of the generated random numbers by reducing classical noise contamination.
Solution Approach 2:
Before the optical pulses undergo interference, an optical switch or gate is used to block the initial portion of each pulse in advance. This preliminary action removes the incoherent segment that would otherwise generate classical noise during interference, ensuring that only the coherent portion of the pulse contributes to the random number generation process.
3Measurement precision
If two photodetectors are used to suppress crosstalk by differential detection, then measurement precision improves, but device complexity increases
Solution Approach 1:
The detection process is segmented into two parallel detection channels using two separate photodetectors. Each photodetector independently detects one of the two interference pulses generated by the interferometer. The outputs of these two detectors are then differentially processed to cancel out common-mode electrical crosstalk and classical noise, thereby improving the precision of the random number generation despite the increased device complexity.
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 number generation rate by effectively utilizing the ADC dynamic range and suppressing classical noise, resulting in improved signal quality and increased performance, particularly in integrated circuits.
Implementation Method 1
uses an optical amplifier to amplify the intensity of the phase-randomised optical pulses
Implementation Method 2
The intensity of the interference pulse is converted by a photodiode to provide an analog voltage signal
Implementation Method 3
the lasing threshold is governed by spontaneous emission, which is a quantum mechanical process, such that the phase of the emitted pulse is random
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A quantum random number generator comprises a laser configured to emit a stream of phase-randomised pulses, an intensity controller configured to modulate a pair of pulses of the stream of phase-randomised pulses, a phase measurement element configured to convert a phase difference between the modulated pair of pulses into an intensity modulation at an output of the phase measurement element, and an optical detector optically coupled to the output of the phase measurement element.