Generation and Spectral Characterization of High-Purity Biphotons
Franco Wong, Massachusetts Institute of Technology
Spectrally factorable biphotons are highly desirable for many photonic quantum information processing tasks such as quantum computation, boson sampling, and quantum repeaters. We generate biphotons with spectral purity of 99%, the highest to date without any spectral filtering, by pulsed spontaneous parametric downconversion in a custom-fabricated PPKTP crystal under extended Gaussian phase-matching conditions. To efficiently characterize the joint spectral intensity of the biphoton output at high spectral resolution, we employ a commercially available dispersion compensation module (DCM) with a dispersion equivalent to 100 km of standard optical fiber and with an insertion loss of only 2.8 dB. Because the dispersion amount and center wavelength of DCMs can be easily customized, spectral characterization in a wide range of quantum photonic applications should benefit significantly from this technique.