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QI: Fachverband Quanteninformation

QI 1: Certification and Benchmarking of Quantum Systems

QI 1.5: Vortrag

Montag, 10. März 2025, 12:15–12:30, HS IX

Detecting high-dimensional time-bin entanglement in a fiber-loop architecture — •Niklas Euler and Martin Gärttner — Institut für Festkörpertheorie und Optik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany

Many quantum-communication protocols require the distribution of entanglement between the different participating parties. One example of such a protocol is quantum key distribution (QKD), an application which has matured to the brink of commercial use in recent years. However, difficulties remain, especially with noise resilience and channel capacity in long-distance communication. One way to overcome these problems is to use high-dimensional entanglement, which has been shown to be more robust to noise and facilitates higher secret-key rates. It is therefore important to have access to certifiable high-dimensional entanglement sources to confidently implement advanced QKD protocols. Here, we investigate a fiber-loop setup that allows the scalable creation of time-bin entanglement and its certification on the same device. Our certification method builds on previous proposals for the certification of angular-momentum entanglement in photon pairs. In particular, measurements in only two experimentally accessible bases are sufficient to obtain a lower bound on the entanglement dimension for both two- and multiphoton quantum states. Numerical simulations show that the method is robust against typical experimental noise effects and works well even with limited measurement statistics, thus establishing time-bin encoded photons as a viable candidate for high-dimensional QKD.

Keywords: High-dimensional entanglement; Time-bin encoding; Discrete-time quantum walk; Entanglement certification; Fiber-loop architecture