European researchers have met a key requirement for space-based quantum technologies by demonstrating a polarization entangled photon generation rate exceeding one gigahertz. The team reports achieving 1.48GHz, a quantifiable milestone for applications like secure communication and advanced computing, using a novel optical bench demonstrator.
This system uniquely creates its own 780nm pump source via second harmonic generation within a periodically poled lithium niobate waveguide, optimized for smooth integration with standard fiber optic cables, Covesion says. Measurement of the CHSH parameter (2 < S = 2.73 <2.83) demonstrates photon entanglement; a CHSH S greater than 2 confirms entanglement.
PPLN Waveguide Design for High-Efficiency SPDC & SHG
Engineered periodically poled lithium niobate waveguides now facilitate efficient photon pair generation, a critical component for quantum technologies, and have been released as a commercial product by Covesion. These waveguides perform both second harmonic generation and spontaneous parametric down conversion, optimized for single mode operation at 1560nm with a mode field diameter matched to standard PM1550 fiber patch cords, ensuring high coupling efficiency for existing fiber optic infrastructure.
An optical bench demonstrator has been designed and built using a three-stage process, beginning with a PPLN waveguide to perform second harmonic generation of an amplified 1560nm telecoms laser, generating the necessary 780nm pump source internally. The team reports achieving a pair generation rate exceeding 1GHz, directly meeting a key requirement defined by the European Space Agency.
Measurement of the pair generation rate, in the low-gain regime, demonstrates a maximum pair generation rate of 1.48GHz at a 0.1 mean photon number. Covesion offers the waveguide in a fiber-coupled package, compatible with both PM1550 and PM850 fiber, making it suitable for both second harmonic generation and spontaneous parametric down conversion, and expanding its potential applications beyond entangled photon sources, according to the company. This release signals a move toward wider accessibility of high-performance quantum components.
Gigahertz-Rate Entangled Photon Generation & CHSH Parameter Validation
This performance was validated through CHSH parameter measurement, yielding a value between 2 and 2.83, which unequivocally demonstrates entanglement. The high pair generation rate, measured in a low-gain regime, translates to a calculated maximum secret key rate of 0.633 Gbps for a BB84 quantum key distribution protocol with 98% polarization discrimination fidelity. Covesion now offers this waveguide as a commercial product, streamlining access to high-performance quantum components for other researchers and developers.
Further development focuses on miniaturization, complete fiberization and pump laser integration to reduce the system’s size, weight, power consumption and cost. Detailed performance data, including polarization entanglement measurements and pair generation rates, is available in a recent publication. The successful demonstration of a gigahertz-rate entangled photon source marks a step toward scalable and practical quantum communication networks.
See today’s quantum computing news on Quantum Zeitgeist for the latest breakthroughs in qubits, hardware, algorithms, and industry deals.
