Nonclassical 2-photon interference with separate intrinsically narrowband fibre sources

Abstract

In this paper, we demonstrate a source of photon pairs based on four-wave-mixing in photonic crystal fibres. Careful engineering of the phase matching conditions in the fibres enables us to create photon pairs at 597 nm and 860 nm in an intrinsically factorable state showing no spectral correlations. This allows for heralding one photon in a pure state and hence renders narrow band filtering obsolete. The source is narrow band, bright and achieves an overall detection efficiency of up to 21% per photon. For the first time, a Hong-Ou-Mandel interference with unfiltered photons from separate fibre sources is presented.

Conversion efficiency in the process of copolarized spontaneous four-wave mixing

“…[6,21,28] that it is possible to engineer the spectral entanglement properties of photon pairs generated by SFWM sources. Recent experimental results [24,29,30] confirm the ability of engineered sources to generate, in particular, factorable photon pairs. In this context, it is natural to ask how the conversion efficiency depends on the type of spectral correlations observed, a question which represents the focus of this section.…”

Optimized heralding schemes for single photons

“…These phase-matching parameters correspond to the signal photon traveling at a much slower group velocity than the pump pulse, while the idler photon travels at the pump-pulse velocity. In the joint two-photon spectrum, the underlying two-photon state corresponds to an ellipse squeezed along the axis of the signal-photon frequency [26]. As shown, the heralding performance in this case is lower than is achievable with the non-factorable state by applying spectral and temporary filtering.…”

“…This interesting fact suggests that the key to achieving high performance in the heralded creation of single photons is to apply an appropriate measurement scheme to the signal photons. This approach is distinctly superior to the much recent effort that has been devoted to tailoring the phase-matching properties of nonlinear media in order to obtain spectrally factorable photon-pair states [12,13,16,[23][24][25][26][27].…”

Temporally uncorrelated photon-pair generation by dual-pump four-wave mixing

“…Especially two cases have been exhaustively studied and demonstrated, for which the JTA is oriented either horizontally (vertically) [18] or at an angle of −45 • [17]. However, both of these configurations exhibit strong abrupt changes in nonlinear interaction at the waveguide endpoints resulting in the well-known sinc-like behavior of the joint spectral amplitude [13,21]. The JTAs of these configurations have recently been carefully analyzed in Ref.…”

“…However, all of these methods share a common downside in that they result in additional photon losses and, consequently, lead to lower * jesbch@fotonik.dtu.dk single-photon rates. This has provided an incentive, leading researchers to a search for a means of reducing the need for postprocess filtering and, in fact, much success has been achieved by carefully controlling the dispersion properties of the nonlinear optical waveguide [17][18][19][20][21][22][23]. The research has almost exclusively been focused on single-pump configurations, even though such schemes, without filtering, do not allow for entirely pure heralded single photons.…”