High-purity single-mode photon source for integrated quantum photonics

Abstract

Integrated quantum photonics relies critically on photon sources that have great purity, single-mode property, scalability, integrability and flexibility for both integrated quantum computing and long-haul quantum communication. Here we report a photon-pair/single-photon source that utilizes cavity-enhanced four-wave mixing in a high-Q silicon microresonator. The photon-pair source has a spectral brightness of 6.25 × 10 8 pairs/s/mW 2 /GHz and a quantum cross-correlation of g (2) si (0) = (2.58 ± 0.16) × 10 4 . The generated photons are single-mode, with a quantum self-correlation of 1.87 ± 0.05. The heralded single photons has conditional photon autocorrelation g(2) c as low as 0.0075 ± 0.0017 at 5.9 × 10 4 pair/s. Quantum photonic technology has found broad applications ranging from quantum communication, 1 quantum computing, 2 to quantum metrology. 3 Recent advances in integrated quantum photonics 4-6 show great promise for chip-scale quantum information processing with tremendous complexity. A bright, single-mode, high-purity, and integrated source of single photons and/or entangled photon pairs is essential for all these applications, 7-10 particularly for integrated quantum photonic circuits which rely critically on the purity, scalability, integrability, and flexibility of the photon source to support diverse quantum functionalities on a single chip.To date, nearly all photon-pair sources are based upon spontaneous parametric down conversion (SPDC) or four-wave mixing (FWM) in nonlinear optical crystals/waveguides. 8-10 Bulk crystals emit photon pairs into a multimode spatial profile, resulting in a fairly low photon generation/collection efficiency. 10-12 Significant efforts have been devoted in recent years to developing waveguide sources for single-mode emission. 13-17 However, the produced photon pairs generally exhibit a non-factorable spectrum which degrades considerably the quantumstate purity. 8 FWM in silica optical fibers/waveguides recently appears as a promising approach with a great flexibility of engineering photon spectrum, 18-25 which, unfortunately, suffers seriously from broadband Raman scattering of silica. 21,22,26 Silicon exhibits a strong Kerr nonlinearity for nonlinear optical interaction and a large refractive index enabling tight mode confinement, which has been explored intensively recently for a variety of applications. [27][28][29][30] In particular, single-crystalline silicon has a clean phonon spectrum with Brillouin-zone-center phonons of a welldefined frequency of 15.6 THz and a narrow linewidth of ∼105 GHz, which eliminates the deleterious broadband Raman noises. 27, 31 These superior features together with mature nanofabrication technology make silicon an ideal platform for integrated quantum photonic application. 32-44Here we propose and demonstrate an ultra-bright high-purity chip-scale photon source on the silicon-oninsulator (SOI) platform. By taking advantage of the dramatic cavity enhanced four-wave mixing in a high-quality silicon microdisk resonator, we are able to...