Polariton lasing is demonstrated on the zero dimensional states of single GaAs/GaAlAs micropillar cavities. Under non resonant excitation, the measured polariton ground state occupancy is found to be as large as 10 4 . Changing the spatial excitation conditions, competition between several polariton lasing modes is observed, ruling out Bose-Einstein condensation. When the polariton state occupancy increases, the emission blueshift is the signature of self-interaction within the halflight half-matter polariton lasing mode.PACS numbers: 78.55. Et, 71.36.+c, 78.45.+h Boson statistics can lead to massive occupation of a single quantum state and trigger final state stimulation. This stimulation is responsible for the bright coherent emission of light in a laser. Another fascinating property of massive bosons in thermal equilibrium is their ability to accumulate in the lowest energy state under a given critical temperature. First predicted in 1925,[1] the experimental observation of Bose Einstein condensation was achieved in the mid 1990s for ultra-cold atoms. [2,3] Demonstrating such bosonic effects with matter waves in a solid state system is very interesting both from fundamental point of view but also for applications since it could provide a new source of coherent light. Cavity polaritons are an example of quasi-particles behaving as bosons at low density. [4,5] They are the exciton-photon mixed quasi-particles arising from the strong coupling regime between quantum well (QW) excitons and a resonant optical cavity mode. Because of their very small effective mass (10 −8 times that of the hydrogen atom) cavity polaritons are expected to condensate at unusually high temperatures (up to room temperature in wide band gap microcavities).[6] These last years, massive occupation of a polariton state has been observed in semiconductor two-dimensional (2D) cavities and attributed to Bose Einstein condensation [7,8] or to polariton lasing. [9] More recently, polariton condensation has been claimed in a localized energy trap [10] where the trap dimensions are sufficiently large for the system to present a 2D continuum of polariton states. In these experiments, the clear distinction of a thermodynamic phase transition (Bose Einstein condensation) from a kinetic stimulated scattering (polariton lasing) is still debated.In this letter, we demonstrate polariton lasing in micrometric sized GaAs/GaAlAs micropillar cavities. In such zero-dimensional (0D) cavities, polariton states are confined in all directions and present a well defined discretized energy spectrum. [11,12] The absence of translation invariance lifts the wave-vector conservation selection-rules in polariton scatterings. In GaAs 2D microcavities, these selection rules are responsible for inefficient polariton-phonon or polariton-polariton scattering, preventing the build-up of a large occupancy in the lower energy states. [13,14,15,16] In this work, we show that polariton scattering is very efficient in micropillar cavities. Under non resonant excitation, a thres...

We demonstrate efficient generation of correlated photon pairs by spontaneous four wave mixing in a 5 μm radius silicon ring resonator in the telecom band around 1550 nm. By optically pumping our device with a 200 μW continuous wave laser, we obtain a pair generation rate of 0.2 MHz and demonstrate photon time correlations with a coincidence-to-accidental ratio as high as 250. The results are in good agreement with theoretical predictions and show the potential of silicon micro-ring resonators as room temperature sources for integrated quantum optics applications.

Artificial neural networks are the heart of machine learning algorithms and artificial intelligence protocols. Historically, the simplest implementation of an artificial neuron traces back to the classical Rosenblatt's "perceptron", but its long term practical applications may be hindered by the fast scaling up of computational complexity, especially relevant for the training of multilayered perceptron networks. Here we introduce a quantum information-based algorithm implementing the quantum computer version of a perceptron, which shows exponential advantage in encoding resources over alternative realizations. We experimentally test a few qubits version of this model on an actual small-scale quantum processor, which gives remarkably good answers against the expected results. We show that this quantum model of a perceptron can be used as an elementary nonlinear classifier of simple patterns, as a first step towards practical training of artificial quantum neural networks to be efficiently implemented on near-term quantum processing hardware.

Entanglement is a fundamental resource in quantum information processing. Several studies have explored the integration of sources of entangled states on a silicon chip, but the devices demonstrated so far require millimeter lengths and pump powers of the order of hundreds of milliwatts to produce an appreciable photon flux, hindering their scalability and dense integration. Microring resonators have been shown to be efficient sources of photon pairs, but entangled state emission has never been proven in these devices. Here we report the first demonstration, to the best of our knowledge, of a microring resonator capable of emitting time-energy entangled photons. We use a Franson experiment to show a violation of Bell’s inequality by more than seven standard deviations with an internal pair generation exceeding 10⁷ Hz. The source is integrated on a silicon chip, operates at milliwatt and submilliwatt pump power, emits in the telecom band, and outputs into a photonic waveguide. These are all essential features of an entangled state emitter for a quantum photonic network

We demonstrate the generation of quantum-correlated photon pairs combined with the spectral filtering of the pump field by more than 95 dB on a single silicon chip using electrically tunable ring resonators and passive Bragg reflectors. Moreover, we perform the demultiplexing and routing of signal and idler photons after transferring them via an optical fiber to a second identical chip. Nonclassical two-photon temporal correlations with a coincidence-to-accidental ratio of 50 are measured without further off-chip filtering. Our system, fabricated with high yield and reproducibility in a CMOS-compatible process, paves the way toward large-scale quantum photonic circuits by allowing sources and detectors of single photons to be integrated on the same chip.