Experimental entanglement generation for quantum key distribution beyond 1 Gbit/s

Abstract

Top-performance sources of photonic entanglement are an indispensable resource for many applications in quantum communication, most notably quantum key distribution. However, up to now, no source has been shown to simultaneously exhibit the high pair-creation rate, broad bandwidth, excellent state fidelity, and low intrinsic loss necessary for gigabit secure key rates. In this work, we present for the first time a source of polarization-entangled photon pairs at telecommunication wavelengths that covers all these needs of real-world quantum-cryptographic applications, thus enabling unprecedented quantum-secure key rates of more than 1 Gbit/s. Our source is designed to optimally exploit state-of-the-art telecommunication equipment and detection systems. Any technological improvement of the latter would result in an even higher rate without modification of the source. We discuss the used wavelength-multiplexing approach, including its potential for multiuser quantum networks and its fundamental limitations. Our source paves the way for high-speed quantum encryption approaching present-day internet bandwidth.

Ultrabright Polarization-Entangled Photon Pair Source for Frequency-Multiplexed Quantum Communication in Free-Space

“…For a detailed analysis on the optimal working point of entangled photon sources in CW operational regime, we refer to the recent work by Neumann et al [16]. The improvement via a wavelength demultiplexing scheme to achieve higher channel capacity, and multi-user operation, has been recently reported for the telecom range by Neumann et al [17].…”

GHz-pulsed source of entangled photons for reconfigurable quantum networks

“…In the context of quantum cryptography, entanglement-based quantum key distribution has recently received considerable attention due to its inherent simplicity. It leverages the intrinsic randomness of quantum entanglement and can be implemented with passive optical components [3,4]. Moreover, it allows for scalable multiuser operation through the use of auxiliary frequency correlations for multiplexing [5,6].…”

Frequency-bin entanglement from domain-engineered down-conversion

“…The waveplates in the tomography setup also impart different unitaries across the full bandwidth of the downconverted photons which reduces the purity of the reconstructed state. This can be mitigated by reconstructing the polarisation state of each bin individually using WDM filters [28] or again using achromatic optics.…”