Versatile and precise quantum state engineering by using nonlinear interferometers

Abstract

The availability of photon states with well-defined temporal modes is crucial for photonic quantum technologies. Ever since the inception of generating photonic quantum states through pulse pumped spontaneous parametric processes, many exquisite efforts have been put on improving the modal purity of the photon states to achieve single-mode operation. However, because the nonlinear interaction and linear dispersion are often mixed in parametric processes, limited successes have been achieved so far only at some specific wavelengths with sophisticated design. In this paper, we resort to a different approach by exploiting an active filtering mechanism originated from interference fringe of nonlinear interferometer. The nonlinear interferometer is realized in a sequential array of nonlinear medium, with a gap in between made of a linear dispersive medium, in which the precise modal control is realized without influencing the phase matching of the parametric process. As a proof-of-principle demonstration of the capability, we present a photon pairs source using a two-stage nonlinear interferometer formed by two identical nonlinear fibers with a standard single mode fiber in between. The results show that spectrally correlated two-photon state via four wave mixing in a single piece nonlinear fiber is modified into factorable state and heralded single-photons with high modal purity and high heralding efficiency are achievable. This novel quantum interferometric method, which can improve the quality of the photon states in almost all the aspects such as modal purity, heralding efficiency, and flexibility in wavelength selection, is proved to be effective and easy to realize.

Biphoton shaping with cascaded entangled-photon sources

“…In this strategy, the pump coherence plays a major role in obtaining various biphoton states. With a long-coherence pump, the entire cascade structure can be considered as one unified source, capable of generating biphotons with tunable spectral properties [58][59] ; in fact, one can obtain various biphoton spectra (Fig. 7) simply by engineering the dispersion of the linear medium in the middle section.…”

Nonlinear interference in crystal superlattices

“…Earlier works theoretically analysed the multicrystal interference in the frequency domain for a single spatial mode 31,34,35 . Analysis of the interference in both the frequency and spatial domains was limited to only two nonlinear crystals 36,37 .…”

“…Then, from Eq. (5), the intensity distribution of the signal photons as a function of frequency ω s and scattering angle θ s , as measured in the experiment, is given by 31,35,38 :…”

“…As one can see, the interference pattern contains additional contributions originating from interferometers with different gaps. The ability to manipulate the interference patterns opens up possibilities for quantum state engineering 20,35 .…”

Tunability of the Nonlinear Interferometer Method for Anchoring Constructive Interference Patterns on the ITU-T Grid

“…Recently, a new method of engineering the quantum states with nonlinear interference (NLI) is proposed and demonstrated [18][19][20]. The NLI system consists of two identical nonlinear media and one linear dispersive medium, which is placed in between them.…”