Tunable quantum beat of single photons enabled by nonlinear nanophotonics
Qing Li, Anshuman Singh, Xiyuan Lu, John R. Lawall, Varun B. Verma, Richard P. Mirin, Sae Woo Nam, Kartik A. Srinivasan
Integrated photonics is a promising approach for scalable implementation of diverse quantum resources at the chip-scale. Here, we demonstrate the integration of two essential building blocks for quantum information science - quantum sources and frequency converters - in the silicon photonics platform. Both functionalities are realized through the chi^(3) nonlinearity in Si3N4 microring resonators, but through application of two different nonlinear processes. Quantum-correlated photon pairs generated by spontaneous four-wave mixing are subsequently frequency shifted by four-wave mixing Bragg scattering without degrading the level of quantum correlation. We further use frequency conversion to enable tunable quantum interference of the initially non-degenerate photons comprising the pair, and observe the quantum beat of single photons as the photon frequencies are tuned across each other. The inherent high-dimensional nature of the microresonator photon pair source and its synergy with the frequency conversion process may enable sophisticated manipulation of quantum states in the frequency domain.