Entangled Photon Source Using Reversed Four-Wave Mixing

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Solution Overview

Problem

Conventional methods for generating entangled photon pairs using four-wave mixing suffer from Raman scattering, leading to uncertainty in photon directionality and entanglement breakage, which affects the purity of the photon correlation and is detrimental to quantum-based operations.

Innovation Solution

The approach involves reversing the pump operation by using idler and signal photons to generate a pair of pump photons with specific resonant frequencies, minimizing Raman scattering effects by selecting wavelengths that avoid scattering regions and utilizing photonic crystal fibers, and applying orthogonal polarization to achieve entangled states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional four-wave mixing is used to generate entangled photon pairs, then photon pair generation can be achieved, but Raman scattering causes uncertainty in photon directionality and entanglement breakage

Engineering Contradiction:

Improvephoton entanglement purityVSAvoidRaman scattering

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent inverts the conventional four-wave mixing process by using difference frequency generation where high-frequency pump photons are converted to lower-frequency signal and idler photons, rather than the conventional approach of converting low-frequency photons to higher frequencies. This inversion allows operation at wavelengths that avoid Raman scattering regions while maintaining entanglement purity

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the operational parameters by selecting specific wavelength combinations for the pump, signal, and idler photons that fall outside the Raman scattering regions. By carefully choosing frequency parameters and polarization states, the system achieves high-rate photon pair generation without Raman scattering-induced entanglement breakage

Inventive Principle:

Principle #35Parameter changes

2Productivity

If pump power is increased to increase photon pair generation rate, then productivity improves, but Raman scattering effects are enhanced causing more unwanted photons

Engineering Contradiction:

Improvephoton pair generation rateVSAvoidRaman scattering

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the potential harm of Raman scattering into a benefit by operating at wavelength combinations where the Raman scattering regions do not overlap with the signal and idler photon frequencies. This allows high pump powers to be used for increased generation rates without generating unwanted Raman-scattered photons that would contaminate the entangled photon pairs

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If conventional FWM is used with pulse pumping, then photon pair generation can occur, but uncertainty exists regarding whether photons have been formed and received as expected

Engineering Contradiction:

Improvephoton formation confirmationVSAvoidphoton correlation purity

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent employs coincidence detection as a feedback mechanism to confirm that entangled photon pairs have been successfully generated and received. By detecting coincident arrivals of signal and idler photons within a specific time window, the system verifies photon pair formation and maintains information about photon correlation, enabling reliable quantum communication protocols

Inventive Principle:

Principle #23Feedback

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 increases the rate of entangled photon pair generation while maintaining high purity, reducing unwanted photons and ensuring energy and momentum conservation, thus enhancing the reliability of quantum communication and other quantum-based applications.

Implementation Method 1

Conventional approaches to providing the photon pairs include parametric down conversion (PDC) which can utilize bulk optics, and also four-wave mixing (FWM) which can utilize fiber optics

Methodology Applied

Scientific EffectFour-wave mixing:

Implementation Method 2

owing to such effects as Raman scattering, a conventional approach of generating ωi and ωs based upon a pulse comprising a pair of pumped photons ωp1 and ωp2 can lead to uncertainty regarding whether the ωi and ωs photons have been formed and received as expected

Methodology Applied

Scientific EffectRaman scattering:

Data Source

PatentUS9465274B1High-yield entangled single photon source

Publication Date: 2016.10.11 NATIONAL TECHNOLOGY & ENGINEERING SOLUTIONS OF SANDIA LLC

AI summary

The various technologies presented herein relate to utilizing photons at respective idler and signal frequencies to facilitate generation of photons at a pump frequency. A strong pump field can be applied at the ωi and the ωs frequencies, with the generated idler and signal pulses being utilized to generate a photon pair at the ωp frequency. Further, the idler pump power can be increased relative to the signal pump power such that the pump power Pi>pump power Ps. Such reversed operation (e.g., ωi+ωs→ωp1+ωp2) can minimize and/or negate Raman scattering effects. By complying with an energy conservation requirement, the ωi and ωs photons interacting with the material through the four-wave mixing process facilitates the entanglement of the ωp1 and ωp2 photons. The ωi and ωs photons can be respectively formed in different length waveguides with a delay utilized to facilitate common timing between the ωi and ωs photons.