Edinburgh Napier University

  For imparting data security to the end-users in a archetypal fiber-to-the-home (FTTH) network, quantum cryptography (QC) is getting much attention now-a-days. QC or more specifically quantum key distribution (QKD) promises unconditionally secure protocol, the Holy Grail of communication and information security, that is based on the fundamental laws of quantum physics. In this talk, we will discuss our latest experiments on a four-state (Quadrature Phase Shift Keying 'QPSK') RF sub-carrier assisted continuous-variable quantum key distribution (CV-QKD) multiuser network based on ultra low loss quantum channel (pure silica core fiber 'PSCF') and micro-electromechanical systems (MEMS) based add/drop switch. A coherent receiver with local local oscillator (LLO) is implemented, which ideally could not be accessed by eavesdroppers (Eve), aided with digital signal processing (DSP) module for phase noise cancellation (PNC). With 10 Gbit/s QPSK classical WDM signals, we have recorded secure key rates of 8.65 Mbit/s over 20 km and upto 12 Mbit/s over lossless channel. The experimental setup is further extended to a optically switched multiuser network, i.e. multiple Bobs, for implementing add/drop operations to achieve key rates of 5.98 Mbit/s for a 2×2 MEMS switch. It is expected that the proposed cost-effective and energy efficient QKD network can facilitate the practical application of the CV-QKD protocol on commercial scale in near future for smart access networks.