Mm Halder

Narrowband high-fidelity all-fibre source of heralded single photons at 1570 nm.

An all-fibre heralded single photon source operating at 1570 nm has been demonstrated. The device generates correlated photon pairs, widely spaced in frequency, through four-wave mixing in a photonic crystal fibre. Separation of the pair photons and narrowband filtering is all achieved in fibre. The output heralded single photon rate was 9.2 x 10(4) per second, with a counts-to-accidentals ratio of 10.4 and a heralding fidelity of 52 %. Furthermore, narrowband filtering ensured that the output single photon state was near time-bandwidth limited with a coherence length of 4 ps. Such a source is well suited to quantum information processing applications.

Cluster state generation using fibre sources

Pure state single photons are at the heart of optical quantum technologies. We have previously reported the generation of photon pairs by four-wave mixing in a single-mode photonic crystal fibre (PCF) [1] and the use of a new birefringent phase matching scheme which results in the generation of narrowband signal photons, around 0.2 nm in bandwidth, and a factorizable photon pair state with no requirement for spectral filtering [2], leading to increased count rates. Our source is bright, polarized, and tuneable by variable laser wavelength and fibre parameters. Hong-Ou-Mandel (HOM) interference is observed between photons from two of these sources, a requirement for optical quantum information tasks.

Cluster State Generation Using Fibre Sources

By pumping a birefringent photonic crystal fibre in opposite directions we generate time-bandwidth limited entangled photon pairs. Performing a fusion gate on photons from two independent sources we create and characterize a four-qubit cluster state.

Nonclassical interferences with separate fibre sources of intrinsically time bandwidth limited photon pairs

Single photons are at the heart of optical quantum technologies such as quantum cryptography, quantum computing and quantum metrology. To achieve high visibility two-photon interferences, the photons need to be in a pure state which usually is achieved by narrow band filtering. This reduces the overall efficiency of detection (µ) and hence limits current experiments to a photon number of 4–6. To achieve significant count rates for higher order multiphoton experiments (such as a cascaded CNOT or Cluster states) an improvement in µ to over 20% is essential.