Joint spectral characterization of photon-pair sources

Abstract

The ability to determine the joint spectral properties of photon pairs produced by the processes of spontaneous parametric downconversion (SPDC) and spontaneous four wave mixing (SFWM) is crucial for guaranteeing the usability of heralded single photons and polarization-entangled pairs for multi-photon protocols. In this paper, we compare six different techniques that yield either a characterization of the joint spectral intensity or of the closely-related purity of heralded single photons. These six techniques include: i) scanning monochromator measurements, ii) a variant of Fourier transform spectroscopy designed to extract the desired information exploiting a resource-optimized technique, iii) dispersive fibre spectroscopy, iv) stimulated-emission-based measurement, v) measurement of the second-order correlation function g (2) for one of the two photons, and vi) two-source Hong-Ou-Mandel interferometry. We discuss the relative performance of these techniques for the specific cases of a SPDC source designed to be factorable and SFWM sources of varying purity, and compare the techniques' relative advantages and disadvantages.

Einstein-Podolsky-Rosen Energy-Time Entanglement of Narrow-Band Biphotons

“…3(d), we fit the profile with Gaussian shape and obtain the two-photon frequency sum uncertainty ∆(ω as + ω s ) = 2π × (161.78 ± 6.87) kHz. Therefore we estimate the Schmidt number of our biphoton source to be K = 1/ 1 − 1/ 1 + ∆(ω as + ω s )/∆ω s/as 2 2 = 8.03, which confirms the entanglement in frequency domain while a speparable qunatum state takes K = 1 [28]. Combining the result from the previous temporal measurement, we get the joint frequency-time uncertainty product ∆(ω s + ω as )∆(t as − t s ) = 0.063 ± 0.0044,…”

Photonic quantum information processing: A concise review

“…Further tailoring of the crystal's nonlinearity profile [123][124][125] provides photons that are fully uncorrelated in their spectrum 126,127 , completely removing the need for lossy spectral filtering. Investigation of the performance and limitations of periodically poled SPDC sources continues [128][129][130][131] and even tools for complete SPDC optimization are now available 132 .…”

Spectrally pure single photons at telecommunications wavelengths using commercial birefringent optical fiber

“…We substantiate our results by comparing the measured phasematching in the fiber to a theoretical model of the spectral properties of the cross polarized four wave mixing (XFWM) process. The source is further characterized through the measurements of second order coherence and joint spectral intensity using stimulated emission tomography (SET) [39]. We also characterize the inhomogenities in the batch of the fiber using the SET technique and explore the possibility of building multiple identical single photon sources using it.…”