Asynchronous quantum key distribution on a relay network

We show how quantum key distribution on a multi-user, multi-path, network can be used to establish a key between any two end-users in an asynchronous fashion using the technique of bit-transport. By a suitable adaptation of our previous secret-sharing scheme we show that an attacker has to compromise all of the intermediate relays on the network in order to obtain the key. Thus, two end-users can establish a secret key provided they trust at least one of the network relays

Optimized attacks on twin-field quantum key distribution

In twin-field quantum key distribution the two communicating parties, Alice and Bob, each send a weak coherent pulse to a third party stationed between them. The key bits are generated by interference between these pulses, with the results communicated to Alice and Bob. We consider optimized strategies for eavesdropping on the communication built upon state discrimination and quantum non-demolition measurements. We find that the best strategy comprises a two-step process but that even this does not compromise the security of the protocol

Journeys from quantum optics to quantum technology

Sir Peter Knight is a pioneer in quantum optics which has now grown to an important branch of modern physics to study the foundations and applications of quantum physics. He is leading an effort to develop new technologies from quantum mechanics. In this collection of essays, we recall the time we were working with him as a postdoc or a PhD student and look at how the time with him has influenced our research