New publication appeared in Optics Express

05.02.2018

Our publication on “Tuning single-photon sources for telecom multi-photon experiments” appeared in Optics Express.

Multi-photon state generation is of great interest for near-future quantum simulation and quantum computation experiments. To-date spontaneous parametric down-conversion is still the most promising process, even though two major impediments still exist: accidental photon noise (caused by the probabilistic non-linear process) and imperfect single-photon purity (arising from spectral entanglement between the photon pairs). In this work, we overcome both of these difficulties by (1) exploiting a passive temporal multiplexing scheme and (2) carefully optimizing the spectral properties of the down-converted photons using periodically-poled KTP crystals. We construct two down-conversion sources in the telecom wavelength regime, finding spectral purities of > 91%, while maintaining high four-photon count rates. We use single-photon grating spectrometers together with superconducting nanowire single-photon detectors to perform a detailed characterization of our multi-photon source. Our methods provide practical solutions to produce high-quality multi-photon states, which are in demand for many quantum photonics applications.

 

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Optics Express 26, 3 3286-3302 (2018).

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(a) Two ppKTP single-photon sources are pumped by a ps-pulsed laser with a repetition rate of 76 MHz. A multiplexing scheme, which splits and recombines the pump beam via beam splitters (BS), increases the repetition rate to a maximum of 608 MHz. The down-converted signal and idler photons are separated by polarizing beamsplitters (PBS) and coupled into single-mode fibers, which can be directed to one of our various detection apparatus. (b) A cartoon of the doubling of the repetiton rate of the laser.