Optimal analysis of ultra broadband energy-time entanglement for high bit-rate dense wavelength division multiplexed quantum networks

Abstract

We demonstrate an experimental method for measuring energy-time entanglement over almost 80 nm spectral bandwidth in a single shot with a quantum bit error rate below 0.5%. Our scheme is extremely cost-effective and efficient in terms of resources as it employs only one source of entangled photons and one fixed unbalanced interferometer per phase-coded analysis basis. We show that the maximum analysis spectral bandwidth is obtained when the analysis interferometers are properly unbalanced, a strategy which can be straightforwardly applied to most of today's experiments based on energy-time and time-bin entanglement. Our scheme has therefore a great potential for boosting bit rates and reducing the resource overhead of future entanglementbased quantum key distribution systems.

Quantum photonics at telecom wavelengths based on lithium niobate waveguides

“…Note that by properly aligning these two interferometers, entanglement analysis can be further performed in almost 100 standard 50 GHz telecom channel pairs simultaneously without the need to adapt the analyzers as a function of the wavelength. This corresponds to the typical emission bandwidth of a type-0 PPLN/W with a few centimetres of length (↔ 80 nm at 1540 nm), and especially covers the commonly used telecom C-band of wavelengths (1530 − 1565 nm) [154].…”

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

“…We compute a 0.3 % degradation in the visibilities because of this crosstalk. Those extremely high quantum interference visibilities stand as a clear witness of the non-classical correlations existing between the paired photons, as they not only exceed exceed largely the threshold of 1/ √ 2 = 70.7% but also are very close to unity [16,26,28]. Let us stress that these results stand as the highest raw quantum interference visibilities for energy-time entangled photon pairs for micro/nanoscale EPPSs [11-14, 17, 24, 29].…”

“…Exploiting energy-time observables relies in the systematic lack of information of the pairs' creation time within the coherence time of the employed CW pump laser. In practice, twin photons pass through the unbalanced interferometer following either the same path (short-short or long-long) or different paths (long-short, or conversely) [28]. These contributions are distinguished by measuring the arrival times of the idler photons with respect to those of the signal photons using a time interval analyzer (not represented).…”

Photonic quantum information processing: a review

“…Starting from time-bin encoding, where the allowed states are 'early' and 'late', an extension of this scheme to multiple states consists in correlating the arrival time with single-photons' energy [49,164,165]. Relevant applications can be found in quantum communication and quantum key distribution to take advantage of the low decoherence with qubits delivery [49,[164][165][166][167][168][169]. Notwithstanding, frequency-encoded experimental demonstrations have been reported also in the context of quantum computation [170][171][172][173][174][175][176] often operating with cluster states.…”