An IEEE study successfully demonstrated robust time-bin entanglement for quantum communication. Researchers achieved high-quality entanglement with approximately 93% visibility using off-the-shelf components distributed across Vienna’s fiber network. This deployment-ready source paves the way for practical and scalable quantum networks.
Time-Bin Entanglement Generated with Off-the-Shelf Components
Generating time-bin entanglement traditionally demanded specialized equipment, but this work demonstrates success using readily available parts. The team created entangled photon pairs by modulating laser pulses into the GHz range, then converting them into a visible beam for a spontaneous parametric down-conversion crystal. Entanglement quality was measured using a standard Mach-Zehnder delay line interferometer and a beamsplitter, achieving approximately 93% visibility. This approach represents a significant step towards practical quantum networks because it sidesteps the instability issues of polarization-based entanglement in fiber optics. Researchers successfully distributed this entanglement across Vienna’s fiber network, proving the feasibility of deployment in a metropolitan area. Utilizing commercial components also suggests improved scalability for future quantum communication systems and photonic crystal integration.
93% Visibility Achieved via Mach-Zehnder Delay Line Interferometry
Entanglement quality was rigorously tested using a Mach-Zehnder delay line interferometer combined with a 50/50 beamsplitter, revealing a visibility of approximately 93%. This high visibility surpasses the threshold necessary for secure key generation within quantum key distribution protocols. Achieving this level of performance with a commercially available interferometer marks a departure from previously complex, custom-built systems needed for similar measurements. The demonstrated setup relies on generating time-bin entangled photons through modulated laser pulses at gigahertz frequencies, subsequently converting them into a visible pump beam. This beam interacts with a spontaneous parametric down-conversion crystal to create the entangled pairs; the use of readily available components suggests a pathway toward building more scalable quantum networks.
We implemented a robust sequential time-bin entangled source for quantum key distribution across Vienna’s existing fiber network.
Martin Achleitner from Austrian Institute of Technology (AIT)
