Heralded Single-Photon Source Using Two-Photon Absorption
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Solution Overview
Problem
Current single-photon sources for quantum computing and communications are non-deterministic, often emitting photons at random times and in random numbers, leading to errors and reduced security or throughput.
Innovation Solution
A heralded single-photon source with a correlated photon-pair generator producing bursts of photon pairs, using optical paths and two-photon absorbers to ensure either zero or one photon per burst, and a photon detector providing a heralding signal for odd or even photon counts to control an optical switch, enhancing the probability of single-photon emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional approaches are used to minimize multi-photon emission probability, then multi-photon emission is reduced, but single-photon emission probability becomes very low
Solution Approach 1:
The patent segments the photon detection process by separating photons into two optical paths based on their characteristics (e.g., polarization). One path leads to a TPA that deterministically reduces photon number to 0 or 1, while the other path leads to a detector that provides heralding information. This segmentation allows the system to achieve high single-photon probability without sacrificing emission rate.
Solution Approach 2:
The patent introduces a TPA as an intermediary element in one optical path that mediates the photon number reduction process. The TPA acts as a deterministic filter that ensures only 0 or 1 photons pass through, while the heralding detector in the other path provides information about the photon number without directly affecting the photon stream. This intermediary mechanism resolves the contradiction between reliability and productivity.
2Reliability
If photon-pair generation is increased to improve single-photon probability, then single-photon emission reliability improves, but multi-photon emission and resource complexity increase
Solution Approach 1:
The patent extracts the photon number control function from the main photon stream by directing photons through separate optical paths. One path contains the TPA for deterministic photon number reduction, while the other path contains the heralding detector. This extraction allows the system to achieve high reliability without requiring complex control mechanisms in the main photon path.
Solution Approach 2:
The patent makes the photon-pair generation source multi-functional by designing it to produce photons with distinguishable characteristics (e.g., different polarizations) that can be routed to different optical paths. This universality allows the same photon source to serve both the TPA path and the heralding detector path, reducing overall system complexity while maintaining high single-photon probability.
3Ease of operation
If periodic driving is used to achieve time-defined photon emission, then emission timing is controlled, but random photon number distribution (zero, one, or more) is produced
Solution Approach 1:
The patent implements feedback by using the heralding detector to provide information about the photon number in each pulse. This heralding signal can be used to select or gate the photon stream, ensuring that only pulses with the desired photon number (typically single photons) are used. This feedback mechanism converts the random photon number distribution into a deterministic single-photon source while maintaining periodic timing control.
Solution Approach 2:
The patent introduces dynamics by making the system adaptive to the actual photon number in each pulse through the heralding mechanism. Rather than relying on fixed periodic emission with random photon numbers, the system dynamically selects or gates photons based on real-time detection information, achieving deterministic single-photon emission while maintaining periodic timing control.
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
Increases the probability of single-photon emission to up to 50% per laser pump cycle, reducing the number of cycles required and improving output repetition rate by minimizing zero-photon events, thus moving towards a deterministic single-photon source for quantum applications.
Implementation Method 1
The first and second characteristics may be one of polarization, spatial mode, momentum mode, or frequency characteristics of the photons, and the correlated photon-pair generator may comprise a non-linear medium pumped by a laser such as a parametric down-conversion (PDC) source or a Chi-3 based four wave mixing source
Implementation Method 2
The correlated photon-pair generator may comprise a non-linear medium pumped by a laser such as a parametric down-conversion (PDC) source or a Chi-3 based four wave mixing source
Implementation Method 3
a two photon absorber ('TPA') in the first optical path that, for each burst of photons, reduces the number of first characteristic photons in the first path to zero or one
Implementation Method 4
a photon detector in the second path having a heralding signal output depending on whether the number of photons in the burst is odd or even
Data Source
AI summary
A system and method is provided for a source for a heralded single photon comprising a correlated photon-pair generator that provides bursts of multiple photon pairs that may be odd or even in number of pairs, one of each pair having a first but not a second characteristic and the other of each pair having the second but not the first characteristic; a first optical path for photons of pairs having the first characteristic; a second optical path for photons of pairs having the second characteristic; a two-photon absorber in the first optical path that, for each burst of photons, reduces the number of first characteristic photons in the first path to zero or one, depending on whether the number of photon pairs in the burst is even or odd; a photon detector in the second path having a heralding signal output to indicate when the number of photons in the burst is odd; and an optical switch coupled to the output of the second optical path and connected to operate in response to the heralding signal.