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. 2013:3:2032.
doi: 10.1038/srep02032.

Two-photon interference between disparate sources for quantum networking

A R McMillan  1 , L Labonté, A S Clark, B Bell, O Alibart, A Martin, W J Wadsworth, S Tanzilli, J G Rarity
Affiliations

Two-photon interference between disparate sources for quantum networking

A R McMillan et al. Sci Rep. 2013.

Abstract

Quantum networks involve entanglement sharing between multiple users. Ideally, any two users would be able to connect regardless of the type of photon source they employ, provided they fulfill the requirements for two-photon interference. From a theoretical perspective, photons coming from different origins can interfere with a perfect visibility, provided they are made indistinguishable in all degrees of freedom. Previous experimental demonstrations of such a scenario have been limited to photon wavelengths below 900 nm, unsuitable for long distance communication, and suffered from low interference visibility. We report two-photon interference using two disparate heralded single photon sources, which involve different nonlinear effects, operating in the telecom wavelength range. The measured visibility of the two-photon interference is 80 ± 4%, which paves the way to hybrid universal quantum networks.

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Figures

Figure 1
Figure 1. Schematic of a quantum network connecting distant users through the connection of various nodes where entanglement is created or measured.
The arrows define the direction to which entanglement is distributed.
Figure 2
Figure 2. Setup combining the MF-based and PPLN/W source (left and right side of diagram).
The 1553 nm photons from both sides are filtered using FBG filters and are combined at a 50:50 fused fibre beamsplitter (BS). The two sources act as heralded single photon sources thanks to the detection of the 809 nm photons which herald the idler photons at 1553 nm. R: retroreflector; M: mirror; WDM: wavelength division multiplexer; C: circulator; FBG: fibre Bragg grating filters; PC: polarization controller; APD: avalanche photodiode; &: FPGA logic system for recording four-fold coincidences.
Figure 3
Figure 3. Net four-fold coincidence rate as a function of the relative delay between idler photons at the BS, adjusted using the retroreflector on the MF source side.
The acquisition time for data was 56 minutes at each point. The error bars are calculated based on a Poissonian distribution for the measured counts. The line shows a fit to the data, which is a sinc-squared function due to the near square shape of the spectral filtering provided by the narrowband FBGs.
See this image and copyright information in PMC

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