Entanglement distribution over 150 km in wavelength division multiplexed channels for quantum cryptography

Abstract

7 pages, 5 figuresInternational audienceGranting information privacy is of crucial importance in our society, notably in fiber communication networks. Quantum cryptography provides a unique means to establish, at remote locations, identical strings of genuine random bits, with a level of secrecy unattainable using classical resources. However, several constraints, such as non-optimized photon number statistics and resources, detectors' noise, and optical losses, currently limit the performances in terms of both achievable secret key rates and distances. Here, these issues are addressed using an approach that combines both fundamental and off-the-shelves technological resources. High-quality bipartite photonic entanglement is distributed over a 150 km fiber link, exploiting a wavelength demultiplexing strategy implemented at the end-user locations. It is shown how coincidence rates scale linearly with the number of employed telecommunication channels, with values outperforming previous realizations by almost one order of magnitude. Thanks to its potential of scalability and compliance with device-independent strategies, this system is ready for real quantum applications, notably entanglement-based quantum cryptography

Passively stable distribution of polarisation entanglement over 192 km of deployed optical fibre

“…The distribution of entanglement through fibre-optic arXiv:1907.04864v1 [quant-ph] 10 Jul 2019 cables has been predominantly focused on time-bin entanglement [10][11][12][13][14], where the entangled degree of freedom between the two photons is temporal, i.e., related to the order in which the photons arrive, as opposed to their polarisation. The former has been demonstrated over two 150 km arms [13], while the latter has been demonstrated over a single arm consisting of a 100 km fibre spool [15].…”

High-quality photonic entanglement for wavelength-multiplexed quantum communication based on a silicon chip

“…On the quantum communication side, current integrated circuits operate almost exclusively in the single mode regime, and typically underexploit the tremendous abilities offered by standard fiber optical technologies. In the perspective of improving quantum key distribution (QKD) systems, a key step lies in the development of robust and reliable devices, showing straightforward compatibility with telecom standards and, consequently, with multimodal operations in the spectral domain [2][3][4][5][6].…”

High-quality photonic entanglement out of a stand-alone silicon chip

“…This SNR can be improved by using a lower pump power at the price of reduced coincidence counts and of longer integration times [39]. There, our strategy is slightly different and promotes pragmatic realizations of QIS experiments by emphasizing high-coincidence counts while keeping a moderate but safe SNR [9].…”

“…Energytime quantum correlation are revealed by the coherent superposition of the contributions coming from identical two-photon paths (short-short and long-long) contrarily to the contributions coming from different paths (longshort, or conversely). Consequently, a coincidence histogram with the emergence of 3 peaks is recorded [9] (Fig. 3b).…”

“…We extend our investigations according the same methodology for subsequent paired-channels within the S-band and the full C-band [30]. More precisely, we explore the entanglement quality of 9 extra pairedchannels, i.e up to 11-FSR shift, spaced by 40 nm (1515-1555 nm) on both sides of the pump channel, leading to the ability of supporting a high number of users in a multiplexing scenario [9]. The details for the signal and idler wavelengths corresponding to i-FSR shift, with 2 ≤ i ≤ 11, are reported in the Methods.…”