Witnessing effective entanglement over a 2km fiber channel

Abstract

We present a fiber-based continuous-variable quantum key distribution system. In the scheme, a quantum signal of two non-orthogonal weak optical coherent states is sent through a fiber-based quantum channel. The receiver simultaneously measures conjugate quadratures of the light using two homodyne detectors. From the measured Q-function of the transmitted signal, we estimate the attenuation and the excess noise caused by the channel. The estimated excess noise originating from the channel and the channel attenuation including the quantum efficiency of the detection setup is investigated with respect to the detection of effective entanglement. The local oscillator is considered in the verification. We witness effective entanglement with a channel length of up to 2km.

11 pages, 5 figures

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• Attacks on practical quantum key distribution systems (and how to prevent them)
• Trusted detector noise analysis for discrete modulation schemes of continuous-variable quantum key distribution
• Classifying, quantifying, and witnessing qudit-qumode hybrid entanglement
• Characterizations and Quantifications of Macroscopic Quantumness and Its Implementations using Optical Fields
• Optimal working points for continuous-variable quantum channels
• Strong quantitative benchmarking of quantum optical devices
• Depolarized guided acoustic wave Brillouin scattering in hollow-core photonic crystal fibers
• Quantum benchmarking with realistic states of light
• CHSH Bell Tests For Optical Hybrid Entanglement