Past Events

Abstract
 

Quantum key distribution (QKD) has been a promising candidate for establishing secure quantum communication, as it is based solely on the laws of quantum mechanics and proven to be unconditionally secure. However, QKD alone is practical in limited distance (~300km) due to the exponential scaling of error probability with communication distance. To extend the range of QKD, one approach is to deploy quantum repeater, a device that makes use of entanglement generation and entanglement swapping to generate an entangled pair of particles in long distance, which can be used in QKD to create a shared secret key between two communicating parties for secure communication.

This solution is simple but suffers from a staggering demand for quantum memory. In recent years, an all-photonic quantum repeater protocol has been proposed. It circumvents the quantum memory problem under a clever use of time reversal and has a polynomial scaling of resource overhead with distance. Despite the theory of all-photonic quantum repeater is solid, there are still two challenges that make the protocol incompatible with existing technology: Generation of multi-photon graph states and the use of ideal Bell-state measurement (BSM). In this seminar, I focus on the second challenge by analyzing the use of realistic BSM in the protocol with 99% input photon loss, detector dark counts and inefficiency. Under these practical imperfections, I found a more realistic upper bound for communication distance. The upper bound may serve as a reference for the experimental implementation of all-photonic quantum repeater in a long distance QKD-based quantum internet.

Anyone interested is welcome to attend.