Cryostat Clock Generation from Pump Photons for Photonic Quantum Timing
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Solution Overview
Problem
Photonic quantum computers require accurate clock signals for precise timing control of optical elements, but existing methods face challenges due to random phase errors and non-deterministic nature of heralding signals, making it difficult to generate suitable clock signals for these systems.
Innovation Solution
A system is developed that generates clock signals using excess pump photons within a cryostat, where a pump photon source outside the cryostat produces pulses that are converted into photon pairs by a photon-pair source inside, with a photodetector and clock generator converting these photons into electrical pulses to produce clock signals at a specific repetition rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If heralding signals are used to generate clock signals, then photon generation can be detected, but random phase errors and non-deterministic nature make accurate timing control difficult
Solution Approach 1:
The patent extracts the clock signal generation function from the heralding signal path by using excess pump photons that do not participate in photon pair generation. This separates the timing reference generation from the quantum signal generation, eliminating the phase errors and non-deterministic nature inherent in heralding-based approaches.
Solution Approach 2:
The patent creates a copy of the pump pulse timing information through the photodetector that detects excess pump photons. This optical copy is then converted to electrical clock signals, providing an accurate timing reference that mirrors the original pump pulse sequence without the phase instability of heralding signals.
2Ease of operation
If pump photons are used outside the cryostat, then clock signals can be generated, but phase drift occurs due to temperature differences between inside and outside the cryostat
Solution Approach 1:
The patent uses excess pump photons as an intermediary carrier to transfer timing information from the room-temperature pump source to the cryostat environment. The photodetector inside the cryostat detects these photons and generates electrical signals, serving as a mediator that bridges the temperature boundary while maintaining phase coherence.
Solution Approach 2:
The patent replaces mechanical/thermal coupling (which would cause phase drift across temperature boundaries) with optical coupling through waveguides. The excess pump photons travel through the waveguide from the room-temperature region to the cryostat, eliminating thermal expansion and mechanical stress that would otherwise cause phase instability.
3Productivity
If all pump photons are converted to photon pairs, then maximum photon generation efficiency is achieved, but no excess photons remain for clock signal generation
Solution Approach 1:
The patent makes the system self-sufficient by using a portion of the pump photons (excess photons that would otherwise be wasted) to generate clock signals internally. This eliminates the need for external clock sources and reduces system complexity, as the quantum optical system itself provides its own timing reference.
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 method ensures clock signals with low phase noise and small drift, synchronized with the photon generation rate, effectively addressing the challenges of random phase errors and non-deterministic signal generation, thereby enhancing the performance of photonic quantum computers.
Implementation Method 1
a photodetector disposed inside the cryostat and configured to receive the second portion of each pump photon pulse of the plurality of pump photon pulses generate a plurality of electrical pulses by converting the second portion of each pump photon pulse of the plurality of pump photon pulses into a respective electrical pulse of the plurality of electrical pulses
Implementation Method 2
a photon-pair source disposed inside the cryostat and optically coupled to the pump photon source via a waveguide. The photon-pair source is configured to receive the plurality of pump photon pulses via the waveguide, convert a first portion of each of a subset of the plurality of pump photon pulses into a photon pair
Data Source
AI summary
A system for generating clock signals for a photonic quantum computing system includes a pump photon source configured to generate a plurality of pump photon pulses at a first repetition rate, a waveguide optically coupled to the pump photon source, and a photon-pair source optically coupled to the first waveguide. The system also includes a photodetector optically coupled to the photon-pair source and configured to generate a plurality of electrical pulses in response to detection of at least a portion of the plurality of pump photon pulses at the first repetition rate and a clock generator coupled to the photodetector and configured to convert the plurality of electrical pulses into a plurality of clock signals at the first repetition rate.