Generation of spectrally uncorrelated biphotons via fiber nonlinear quantum interference

Abstract

Spectrally uncorrelated biphotons are the essential resources for achieving various quantum information processing protocols. We theoretically investigate the generation of spectrally uncorrelated biphotons emitted by spontaneous four-wave mixing from a fiber nonlinear interferometer which consists of an N-stage nonlinear gain fiber and an (N-1)-stage dispersion modulation fiber. The output biphoton states of nonlinear interference are the coherent superposition of various biphoton states born in each nonlinear fiber, and thus the interference fringe will reshape the biphoton joint spectra. As a result, resorting to Taylor expansion to first order for phase mismatching, we theoretically verify that the orientation of phase matching contours will rotate in a specific way with only varying the length of dispersion modulation fiber. The rotation in orientation of phase matching contours may result in spectrally uncorrelated biphotons and even arbitrary correlation biphotons. Further, we choose micro/nanofiber as the nonlinear gain fiber and single-mode communication fiber as dispersion modulation fiber to numerically simulate the generation of spectrally uncorrelated biphotons from spontaneous fourwave mixing. Here, due to significant frequency detuning (hundreds of THz), Raman background noise can be considerably suppressed, even at room temperature, and photons with largely tunable wavelengths can be achieved, indicating a practicability in many quantum fields. A photon mode purity of 97.2% will be theoretically attained without weakening the heralding nature of biphoton sources. We think that this fiber nonlinear interference with the flexibly engineered quantum state can be an excellent practical source for quantum information processing.