SECRET

SECuRe quantum communication based on Energy-Time/time-bin entanglement

Quantum communications (QC) is one of the main areas of the broader field of Quantum Technologies. The most well-known application of QC is in communication security, where huge progress has been observed since the first demonstrations of quantum key distribution (QKD). Another important application of QC is as the support backbone for future networks of quantum computers, the so-called Quantum Internet.

Entanglement is a crucial resource in both applications. It allows a higher level of security in QKD, as well as being a requirement in many Quantum Internet communication protocols. Therefore it is very important to ensure that entanglement can be certified, and a very popular way to do it is through a Bell inequality violation.

A particularly important type of photonic entanglement is called energy-time (ET). It has been very popular over the last 25 years or so, since it is very robust against disturbances that affect other types of entanglement over optical fibers. The downside has been that most experimental implementations employ the famous “Franson’s configuration”, which has an inherent flaw called the post-selection loophole that invalidates a Bell inequality violation, unless extra assumptions are present. All members of this consortium have been responsible for proposing and carrying out the first, and so far only performed, QC experiments based on ET (and its pulsed version called time-bin) entanglement that do not present the post-selection flaw, and thus can be used to perform experiments based on “genuine” ET/time-bin entanglement.

This project now aims to carry out the first generation of genuine energy-time/time-bin experiments aimed at final, practical applications. We intend to perform, based on this type of entanglement the first: (i) QKD experiments and (ii) entanglement swapping/teleportation experiments. Furthermore, our project will also perform the first implementations of QKD with genuine energy-time/time-bin entanglement on integrated photonic circuits, as well as strong theoretical analysis on the post-selection loophole in these new experiments. The results proposed will form an important experimental and theoretical framework to support the future development of the Quantum Internet based on the telecommunication optical fibre network.

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