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arXiv:1905.11336 · Physical Review A

Quantum correlations from dynamically modulated optical nonlinear interactions

Usman A. Javid, Qiang Lin

Published Oct 11, 2019• 6 citations
arXivHTMLPDF

Abstract

We investigate optical nonlinear interactions in a dynamic environment by studying the generation of photons in spontaneous parametric down conversion inside a nonlinear cavity where the optical path length is periodically modulated in time. We show that the temporal dynamics of the cavity modify the nonlinear interaction and the generated continuous-variable time-frequency entangled biphoton state evolves into a tunable discrete higher-dimensional state in the nonadiabatic modulation regime where the modulation timescales are much faster than the photon lifetime. In this regime, the system mimics effects of a quantum random walk in a photonic lattice with many associated effects, including localized and delocalized wave functions of the generated photons. We also propose generation of time-frequency hyperentangled states in the adiabatic limit. Our analysis shows that the proposed system is promising for applications in quantum simulation and information processing in the time-frequency domain.

DOI
10.1103/physreva.100.043811

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We investigate optical nonlinear interactions in a dynamic environment by studying the generation of photons in spontaneous parametric down conversion inside a nonlinear cavity where the optical path length is periodically modulated in time. We show that the temporal dynamics of the cavity modify the nonlinear interaction and the generated continuous-variable time-frequency entangled biphoton state evolves into a tunable discrete higher-dimensional state in the nonadiabatic modulation regime where the modulation timescales are much faster than the photon lifetime. In this regime, the system mimics effects of a quantum random walk in a photonic lattice with many associated effects, including localized and delocalized wave functions of the generated photons. We also propose generation of time-frequency hyperentangled states in the adiabatic limit. Our analysis shows that the proposed system is promising for applications in quantum simulation and information processing in the time-frequency domain.
Cavity-assisted spontaneous parametric down-conversion (SPDC) and spontaneous four-wave mixing (SFWM) in nonlinear optical materials are practical and versatile methods to generate narrowband time-energy entangled photon pairs. Time-energy entangled photons with tailored spectro-temporal properties are particularly useful for efficient quantum optical interfaces. In this work we study the generation of photon pairs in cavity-assisted SPDC and SFWM for the general case of off-resonant conversion, namely, when the frequencies of the generated photons do not match the cavity resonances. Such a frequency mismatch in particular depends on temperature and requires an additional control in the experiment. First, we propose a generic model, for description of cavity-assisted SPDC and SFWM. We show that in both processes the mismatch reduces the generation rate of photons, distorts the spectrum and the auto-correlation function of the generated fields, as well as affects the photon generation dynamics. Second, we verify the results experimentally using parametric generation of photon pairs in a nonlinear whispering gallery mode resonator (WGMR) as an experimental platform with controlled frequency mismatch. Our work reveals the role of the frequency mismatch in the photon generation process and shows a way to control it. Obtained results constitute one more step in the direction of full control over the spectro-temporal properties of entangled photon pairs and the heralded generation of single-photon pulses with a tailored temporal mode.
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Abstract Highly coherent frequency-entangled photons at telecom band are critical in quantum information protocols and quantum tele-communication. Photon pairs generated by spontaneous parametric down-conversion in nonlinear crystals or modulation instability in optical fibers exhibit random fluctuations. Here, we demonstrate highly stable frequency-entangled photons based on parametric instability in an active fiber ring cavity, where periodic modulation of dispersion excites parametric resonance, and the characteristic wave number is selected by the periodic modulation of resonator. Background-free autocorrelation of single-shot spectra reveals that spectra of parametric instability sidebands possess high coherence. The quantum properties are tested by the Hanbury Brown-Twiss measurement and Hong-Ou-Mandel interference. We conform the frequency-entanglement of two parametric instability sidebands by a spatial quantum beating with a fringe visibility of 97.9%. Our results prove that the parametric instability in active fiber cavity is effective to generate highly coherent frequency-entangled photon pairs, which would facilitate subsequent quantum applications.
Abstract Many technologies emerging from quantum information science heavily rely upon the generation and manipulation of entangled quantum states. Here, we propose and demonstrate a new class of quantum interference phenomena that arise when states are created in and coherently converted between the propagating modes of an optical microcavity. The modal coupling introduces several new creation pathways to a nonlinear optical process within the device, which quantum mechanically interfere to drive the system between states in the time domain. The coherent conversion entangles the generated biphotons between propagation pathways, leading to cyclically evolving path-entanglement and the manifestation of coherent oscillations in second-order temporal correlations. Furthermore, the rich device physics is harnessed to tune properties of the quantum states. In particular, we show that the strength of interference between pathways can be coherently controlled, allowing for manipulation of the degree of entanglement, which can even be entirely quenched. The states can likewise be made to flip-flop between exhibiting initially correlated or uncorrelated behavior. The phenomena presented here open a route to creating higher dimensional entanglement and exotic multi-photon states.
Quantum entanglement became essential in understanding the non-locality of quantum mechanics. In optics, this non-locality can be demonstrated on impressively large length scales, as photons travel with the speed of light and interact only weakly with their environment. Spontaneous parametric down-conversion (SPDC) in nonlinear crystals provides an efficient source for entangled photon pairs, so-called biphotons. However, SPDC can also be implemented in nonlinear arrays of evanescently coupled waveguides which allows the generation and the investigation of correlated quantum walks of such biphotons in an integrated device. Here, we analytically and experimentally demonstrate that the biphoton degrees of freedom are entailed in an additional dimension, therefore the SPDC and the subsequent quantum random walk in one-dimensional arrays can be simulated through classical optical beam propagation in a two-dimensional photonic lattice. Thereby, the output intensity images directly represent the biphoton correlations and exhibit a clear violation of a Bell-like inequality.