A six-user quantum key distribution over a bus network spanning a total distance 30km of standard telecommunication-grade
fiber is demonstrated. Each user on the network has one unique address wavelength channel for establishing
secure quantum cryptographic keys with a central network server. The address wavelengths are all in the C-band region
of between 1553 nm and 1557 nm, making the system compatible with present fiber-optic communication network
infrastructures. The quantum bit error rate measurements made on the network agree favorably with theoretically
Quantum cryptography applies the uncertainty principle and the no-cloning theorem to allow to parties to share a secret key over an ultra-secure link. Present quantum cryptography technologies provide encryption key distribution only between two users. However, practical implementations of encryption key distribution schemes require establishing secure quantum communications amongst multiple users. This paper looks at some of the advantages and drawbacks of some common network topologies that could be used in sending cryptographic keys across a network consisting of multiple users. These topologies are the star, ring, and bus networks. Their performances are compared and analyzed using quantum bit error rate analysis. The paper also presents an experimental demonstration of a six-user quantum key distribution network implemented on a bus topology.
Quantum cryptography applies the uncertainty principle and the no-cloning theorem of quantum mechanics to provide ultra-secure encryption key distribution between two parties. Present quantum cryptography technologies provide encryption key distribution between two parties. However, practical implementations encryption key distribution schemes require establishing secure quantum communications amongst multiple users. In this talk, we survey some of the state of the art quantum encryption deployment in communication networks. We will also discuss some common topologies that are being considered for multi-user quantum encryption networks. The performance of the multi-user quantum key distribution systems is then compared for four different optical network topologies: the Sagnac-based fiber ring, the wavelength routed, the passive star and the bus network. Their performances are compared and analyzed using quantum bit error rate analysis.
A theoretical model is presented for the interaction of a quantum system with an orthogonal polarized entangled photon-pair measurement probe. The theoretical framework is based on solving the generalized Jaynes-Cummings and Shroeder's equations to determine the phase evolution of the interacting system. The measurement-induced decoherence is expressed in terms of the temporal evolution of the relative phases of the superposition states induced by the measurement probe. The method is applied to determine the rate of decoherence of a two-qubit rubidium quantum system. Quantitative results are given to contrast measurement-induced of (i) single photon probe and (ii) orthogonal polarized and entangled probe.