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Register a new userOn-chip multiplexed multiple entanglement sources in a single silicon nanowire
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Silicon-on-chip (SOI) photonic circuit is the most promising platform for scalable quantum information technology for its low loss, small footprint, CMOS-compatible and telecom communications techniques compatible. Multiple multiplexed entanglement sources include: energy-time, time-bin and polarization entangled sources based on 1-cm length single silicon nanowire, all these sources are compatible with (100GHz) dense-wave-division-multiplexing (DWDM) system. Different methods such as two photon interference pattern, Bell-Inequality and quantum state tomography are used to characterize the quality of these entangled sources. Multiple entanglements are generated over more than 5 channel pairs with high raw (net) visibilities around 97% (100%). The emission spectral brightness of these entangled sources reaches 4.2*105 /(s.nm.mW). The quality of the photon pair generated in continuous and pulse pump regimes are compared. High qualities of these multiplexed entanglement sources make them very promising to be used in future minimized quantum communication and computation systems.
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Entanglement is a counterintuitive feature of quantum physics that is at the heart of quantum technology. High-dimensional quantum states offer unique advantages in various quantum information tasks. Integrated photonic chips have recently emerged as a leading platform for the generation, manipulation and detection of entangled photons. Here, we report a silicon photonic chip that uses novel interferometric resonance-enhanced photon-pair sources, spectral demultiplexers and high-dimensional reconfigurable circuitries to generate, manipulate and analyse path-entangled three-dimensional qutrit states. By minimizing on-chip electrical and thermal cross-talk, we obtain high-quality quantum interference with visibilities above 96.5% and a maximumly entangled qutrit state with a fidelity of 95.5%. We further explore the fundamental properties of entangled qutrits to test quantum nonlocality and contextuality, and to implement quantum simulations of graphs and high-precision optical phase measurements. Our work paves the path for the development of multiphoton high-dimensional quantum technologies.
Quantum technology is playing an increasingly important role due to the intrinsic parallel processing capabilities endorsed by quantum superposition, exceeding upper limits of classical performances in diverse fields. Integrated photonic chip offers an elegant way to construct large-scale quantum systems in a physically scalable fashion, however, nonuniformity of quantum sources prevents all the elements from being connected coherently for exponentially increasing Hilbert space. Here, we experimentally demonstrate 128 identical quantum sources integrated on a single silica chip. By actively controlling the light-matter interaction in femtosecond laser direct writing, we are able to unify the properties of waveguides comprehensively and therefore the spontaneous four-wave mixing process for quantum sources. We verify the indistinguishability of the on-chip sources by a series of heralded two-source Hong-Ou-Mandel interference, with all the dip visibilities above 90%. In addition, the brightness of the sources is found easily reaching MHz and being applicable to both discrete-variable and continuous-variable platform, showing either clear anti-bunching feature or large squeezing parameter under different pumping regimes. The demonstrated scalability and uniformity of quantum sources, together with integrated photonic network and detection, will enable large-scale all-on-chip quantum processors for real-life applications.
Microring resonators are attractive for low-power frequency conversion via Bragg-scattering four-wave-mixing due to their comb-like resonance spectrum. However, conversion efficiency is limited 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 allow localized frequency modes to be converted into propagating continuous-mode photon wave packets using a single operation. The key is that frequency conversion works as a switch on both spatial and spectral degrees of freedom of photons if the microring is interferometrically coupled to a bus waveguide. Our numerical results show 99% conversion efficiency into a propagating mode with a wave packet having a 90% overlap with a Gaussian for a ratio between intrinsic and coupling quality factors of 400.
We demonstrate heralded single photon generation in a CMOS-compatible silicon nanophotonic device. The strong modal confinement and slow group velocity provided by a coupled resonator optical waveguide (CROW) produced a large four-wave-mixing nonlinearity coefficient gamma_eff ~4100 W^-1 m^-1 at telecommunications wavelengths. Spontaneous four-wave-mixing using a degenerate pump beam at 1549.6 nm created photon pairs at 1529.5 nm and 1570.5 nm with a coincidence-to-accidental ratio exceeding 20. A photon correlation measurement of the signal (1529.5 nm) photons heralded by the detection of the idler (1570.5 nm) photons showed antibunching with g^(2)(0) = 0.19 pm 0.03. The demonstration of a single photon source within a silicon platform holds promise for future integrated quantum photonic circuits.
An on-demand single-photon source is a key requirement for scaling many optical quantum technologies. A promising approach to realize an on-demand single-photon source is to multiplex an array of heralded single-photon sources using an active optical switching network. However, the performance of multiplexed sources is degraded by photon loss in the optical components and the non-unit detection efficiency of the heralding detectors. We provide a theoretical description of a general multiplexed single-photon source with lossy components and derive expressions for the output probabilities of single-photon emission and multi-photon contamination. We apply these expressions to three specific multiplexing source architectures and consider their tradeoffs in design and performance. To assess the effect of lossy components on near- and long-term experimental goals, we simulate the multiplexed sources when used for many-photon state generation under various amounts of component loss. We find that with a multiplexed source composed of switches with ~0.2-0.4 dB loss and high efficiency number-resolving detectors, a single-photon source capable of efficiently producing 20-40 photon states with low multi-photon contamination is possible, offering the possibility of unlocking new classes of experiments and technologies.
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