We propose cascaded spontaneous four-wave mixing (SFWM) in microring resonators as a scalable and efficient approach for directly generating non-Gaussian states of light. Focusing on the well-understood "low-gain" regime, we demonstrate that triplet generation through cascaded SFWM can be achieved with high efficiency and favorable spectral characteristics using realistic microring sources in AlGaAs. The ability to achieve the generation of light in a single set of supermodes -- and the predicted accessibility of the "high-gain" regime at realistic pump powers -- makes this source a promising candidate as a direct and deterministic source of non-Gaussian light for photonic quantum information processing.
We propose cascaded spontaneous four-wave mixing (SFWM) in microring resonators as a scalable and efficient approach for directly generating non-Gaussian states of light. Focusing on the well-understood "low-gain" regime, we demonstrate that triplet generation through cascaded SFWM can be achieved with high efficiency and favorable spectral characteristics using realistic microring sources in AlGaAs. The ability to achieve the generation of light in a single set of supermodes -- and the predicted accessibility of the "high-gain" regime at realistic pump powers -- makes this source a promising candidate as a direct and deterministic source of non-Gaussian light for photonic quantum information processing.
Photonic chips with silicon nitride (Si3N4) microring resonators are well established as heralded single-photon sources, but their operation as frequency-degenerate twin-photon sources has not previously been demonstrated. Here, we realise a twin-photon source at telecommunication wavelengths in a Si3N4 ring microresonator via an inverse four-wave mixing (FWM) process, in which two photons from spectrally distinct pumps are converted into a pair of identical twin photons. The measurements show a maximum coincidence-to-accidental ratio (CAR) of 5.4±0.6. In addition, the microresonator functions as a heralded single-photon source through pump-degenerate spontaneous four-wave mixing (SFWM), exhibiting a spectral purity of P=0.67±0.05 and a heralded anti-bunching of gh(2)(0)=0.0042±0.0015. Together, these results demonstrate both photon-generation schemes on a single integrated Si3N4 platform, highlighting its potential for scalable, tailored quantum light generation.
In this talk, the physics of microring resonators is discussed in the classical and quantum regimes, in the context of the exploitation of chi-3 effects in these cavities as done by our group. Through the implementation of a novel microring pumping scheme and a quantum reinterpretation of the frequency comb, we present an integrated platform for the generation of quantum optical states spread over multiple optical modes. The scheme allows for highly stable and potentially fullyintegrable quantum light sources. Following the demonstration of a multiplexed heralded photon source, the scheme also enabled the first demonstration of a new nonlinear process on the integrated platform (type II spontaneous four-wave mixing) allowing the first direct generation of polarization-diverse photon pairs, where the first time two ring modes can be pumped in a stable configuration.
Abstract Photon triplet sources exhibit non-Gaussian features, a key property for applications in quantum computing and quantum information. However, spectral correlations can limit the performance and detection efficiency of these systems. Motivated by this observation, we present a theoretical analysis of the spectral properties of photon triplets generated through spontaneous third-order parametric down-conversion in photonic devices, and discuss strategies to quantify and minimize such correlations. We propose two approaches: dispersion engineering in waveguides and pump engineering in resonators. We apply these strategies in two realistic source designs, namely a high-index-contrast optical fiber and a silicon nitride microring resonator. Finally, we discuss detection strategies for probing non-Gaussian features of the triplet state. We find that it is feasible to achieve few-mode generation of photon triplets using state-of-the-art experimental systems, a crucial step toward practical applications of photon triplet sources in quantum technologies.
Microring resonators are attractive for low-power frequency conversion via Bragg-scattering four-wave-mixing due to their comb-like resonance spectrum, which allows resonant enhancement of all four waves while maintaining energy and momentum conservation. However, the symmetry of such mode structures limits the conversion efficiency to 50% due to the equal probability of up- and down-conversion. Here, we demonstrate how two coupled microrings enable highly directional conversion between the spectral modes of one of the rings. An extinction between up- and down-conversion of more than 40 dB is experimentally observed. Based on this method, we propose a design for on-chip multiplexed single-photon sources that probabilistically generate photon pairs across many frequency modes of a ring resonator and subsequently convert them to a single frequency—thereby enabling quasi-deterministic photon emission. Our numerical analysis shows that once a photon is generated, it can be converted and emitted into a wave packet having a 90% overlap with a Gaussian with 99% efficiency for a ratio between intrinsic and coupling quality factors of 400.
We propose an integrated device, the resonant interferometric coupler, enabling selective control over the coupling condition of a microring resonator. This can be used to tune the resonance linewidths independently, allowing for the targeted engineering of nonlinear optical interactions. We show how this can be applied to spontaneous four-wave mixing for various purposes. In the low-gain regime, we demonstrate the generation of spectrally uncorrelated photon pairs by broadening the pump resonance relative to the signal and idler. In the high-gain regime, we show how parasitic nonlinear processes can be suppressed by inhibiting undesired resonances, leading to a more efficient generation of squeezed light.
In this thesis we study the generation of non-classical states of light using nonlinear integrated photonics. We focus first on third-order parametric down-conversion (TOPDC), a process in which pump photons can be down-converted into photon triplets, and which could serve as a source of non-Gaussian states and tripartite discrete-variable entanglement. We investigate the possibility of implementing TOPDC in conventional integrated structures. By comparing the estimated triplet generation rates in a waveguide and a microring resonator, we establish that non-resonant structures appear to be a more promising platform for a near-term demonstration of TOPDC, due to the high generation bandwidth enhancing the rate of triplet generation. We estimate generation rates of ~10 triplets per second for a 1-cm-long waveguide driven by a 100 mW CW pump, a rate that is comparable to or higher than those quoted for other proposals. We then estimate the non-Gaussianity that might be expected in a supermode of the field generated by our sample structures. The predicted non-Gaussianity is negligible in both structures, for different reasons: The generation rate in the ring is too low, while the field generated by the waveguide is highly multimode. We conclude that although a simple SiN waveguide may be a suitable source for a first demonstration of optical TOPDC, the design will need to be improved significantly for observations of non-Gaussianity or tripartite entanglement in the generated light. Indeed, state generation protocols based on conventional spontaneous four-wave mixing sources and postselection appear to be more promising in the near term. We adopt this approach to design integrated sources of postselected multipartite states in a frequency bin encoding scheme. We introduce sources of W states and GHZ states, with kHz generation rates expected for picojoule pump pulses. This platform appears to be promising for the generation of more arbitrary states, including high-dimensional ones consisting of entangled qudits. We review a graph-based strategy that may be useful for designing other devices, and for understanding the limitations of this platform.