Deterministic Single-Photon Source Using Spectral Shift
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Solution Overview
Problem
Current methods for generating single photons on demand are unreliable due to lossy switches and complexity, especially in systems using multiple optical paths and pump sources, which fail to produce a desired photon efficiently and are costly.
Innovation Solution
A system that uses spectral shifts of heralded photons, employing a secondary laser, modulator, and non-linear optical elements to produce deterministic single photons by measuring and modulating the wavelength of one photon in a correlated pair to generate an output photon of a specific wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If switches are used to select optical paths for different output photon frequencies, then the ability to select desired photon wavelengths is improved, but the system becomes lossy and unreliable due to photon absorption in the switches
Solution Approach 1:
The patent extracts the wavelength selection function from the optical path switching mechanism. Instead of using switches to select different photon paths, the system generates photons directly at the desired wavelength by detecting one photon of a correlated pair and using that information to control the generation process, thereby eliminating the need for wavelength-selective switches and their associated losses.
Solution Approach 2:
The patent introduces an intermediary detection and control mechanism. A heralding detector detects one photon of a correlated pair and uses this information to control the generation of the second photon at a specific wavelength. This intermediary process enables wavelength selection without requiring the photons to pass through lossy wavelength-selective switches.
2Adaptability or versatility
If multiple optical paths and multiple pump sources are used to generate single photons, then the versatility of photon generation is improved, but the system complexity and cost increase significantly
Solution Approach 1:
The patent employs a single pump source that serves multiple functions through the use of non-linear optical crystals that can generate correlated photon pairs at different wavelengths. The same pump laser and crystal system can produce various wavelength combinations, eliminating the need for multiple dedicated pump sources and optical paths while maintaining generation flexibility.
Solution Approach 2:
The patent merges multiple functions into a single integrated system. The heralding detector, non-linear optical crystal, and pump source work together as a unified system where detection of one photon automatically enables controlled generation of the other photon. This integration reduces the number of separate optical paths and components needed compared to traditional multi-source approaches.
3Device complexity
If traditional single-photon sources are used, then the system is simpler, but the probability of generating a single photon on demand is low and multiple photons are frequently produced
Solution Approach 1:
The patent implements a feedback mechanism where the detection of the first photon of a correlated pair provides real-time information that controls the generation process. When a photon is detected by the heralding detector, this detection event triggers the controlled generation of the second photon at a specific wavelength, ensuring that a single photon is produced on demand rather than relying on probabilistic generation.
Solution Approach 2:
The system performs preliminary detection of one photon in the correlated pair before generating the second photon. This preliminary action (heralding detection) confirms that a photon pair has been created and enables subsequent controlled generation, ensuring single-photon precision before the actual output photon is produced.
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 allows for the reliable and efficient generation of single photons with a desired wavelength on demand, reducing losses and system complexity while maintaining high probability of single-pair generation with minimal multiple-pair production.
Implementation Method 1
a non-linear optical element (NLE) is configured to receive the second photon of the pair of correlated photons and the modulated secondary pump beam from the beam combiner and produce an output photon having a wavelength based on wavelengths of the second photon and the modulated secondary pump beam
Implementation Method 2
a modulator situated to receive the secondary pump beam and modulate the secondary pump beam at a frequency based on a wavelength of a first photon of a pair of correlated photons
Data Source
AI summary
An apparatus for producing a single photon can comprise a modulator that modulates the wavelength of a pump beam based on wavelength of an idler photon of a signal/idler photon pair. A wavelength division multiplexer combines the modulated pump beam and the signal photon in a non-linear element to produce an output photon having a preselected wavelength based on signal photon wavelength and a wavelength of the modulated pump beam.