https://doi.org/10.1140/epjqt/s40507-025-00428-0
Research
A Sagnac-based arbitrary time-bin state encoder for quantum communication applications
1
Dipartimento di Ingegneria dell’Informazione, Università degli Studi di Padova, Via Gradenigo 6B, 35131, Padova, Padova, Italy
2
Padua Quantum Technologies Research Center, Università degli Studi di Padova, via Gradenigo 6B, 35131, Padova, Padova, Italy
Received:
11
July
2025
Accepted:
8
October
2025
Published online:
10
November
2025
Time-bin encoding of quantum information is highly advantageous for long-distance quantum communication protocols over optical fibres due to its inherent robustness in the channel and the possibility of generating high-dimensional quantum states. The most common implementation of time-bin quantum states using unbalanced interferometers presents challenges in terms of stability and flexibility of operation. In particular, a limited number of states can be generated without modifying the optical scheme. Here we present the implementation of a fully controllable arbitrary time-bin quantum state encoder, which is easily scalable to arbitrary dimensions and time-bin separations. The encoder presents high stability and low quantum bit error rate (QBER) for all the tested repetition rates and time-bin separations, without requiring hardware modifications. We further demonstrate phase randomisation and phase encoding without the need for additional resources.
Key words: Quantum communication / Quantum key distribution / Entanglement generation / Time-bin encoding / High-dimensional encoding
© The Author(s) 2025
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