Abstract
Hybrid quantum networks rely on efficient interfacing of dissimilar quantum nodes, as elements based on parametric downconversion sources, quantum dots, colour centres or atoms are fundamentally different in their frequencies and bandwidths. Although pulse manipulation has been demonstrated in very different systems, to date no interface exists that provides both an efficient bandwidth compression and a substantial frequency translation at the same time. Here we demonstrate an engineered sum-frequency-conversion process in lithium niobate that achieves both goals. We convert pure photons at telecom wavelengths to the visible range while compressing the bandwidth by a factor of 7.47 under preservation of non-classical photon-number statistics. We achieve internal conversion efficiencies of 61.5%, significantly outperforming spectral filtering for bandwidth compression. Our system thus makes the connection between previously incompatible quantum systems as a step towards usable quantum networks.
Highlights
Hybrid quantum networks rely on efficient interfacing of dissimilar quantum nodes, as elements based on parametric downconversion sources, quantum dots, colour centres or atoms are fundamentally different in their frequencies and bandwidths
Such engineering has been widely exploited for parametric downconversion (PDC)[14,15,16,17] to produce decorrelated photon pairs efficiently
To demonstrate the performance of the quantum pulse gate (QPG) as an interface, we focus on its application as a link between PDC sources and quantum memories to produce on-demand single photons
Summary
Hybrid quantum networks rely on efficient interfacing of dissimilar quantum nodes, as elements based on parametric downconversion sources, quantum dots, colour centres or atoms are fundamentally different in their frequencies and bandwidths. An alternative approach is to engineer the phasematching of the sum-frequency process itself[13] by choosing appropriate group velocity and pump-pulse conditions Such engineering has been widely exploited for parametric downconversion (PDC)[14,15,16,17] to produce decorrelated photon pairs efficiently. We show in this work that dispersion engineering can be used to develop processes that provide spectral reshaping and high conversion efficiencies at the same time We demonstrate such an interface by converting single photons from 1,545 nm and a bandwidth of 1 THz to 550 nm and a bandwidth of 129 GHz under preservation of the second-order correlation function g(2)(0) while achieving external conversion efficiencies high enough to outperform a spectral filter producing an equivalent output spectrum
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