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SEM images of (a) an array of pillar microcavities and (b) a single pillar microcavity (scale bars 20 μm and 2 μm, respectively). (c) a semiconductor waveguide chip (scale bar 5 mm) and (d) Schematic diagram of a single waveguide circuit.
(a) and (b) Pulsed second-order autocorrelation measurement yields . (c) and (d) Pulsed autocorrelation measurement when the QD is excited twice in quick succession shows that the probability of either excitation resulting in multi-photon emission to be . (e) and (f) Pulsed two photon interference measurement using a coupler yields a two photon interference visibility of .
Each pane corresponds to a correlation measurement for a single input and output combination. Measured data are shown as filled red bars. Solid black lines show calculated curves for the expected correlations given the measured coupler ratios, single photon interference visibility, and two photon interference visibility. The peaks at correspond to events where both photons entered the circuit simultaneously, and the area of these peaks is used to extract the truth table for the operation.
(a) Truth table for an ideal CNOT gate. (b) Predicted truth table for the circuit and photon source used in this experiment based on the experimentally achieved two photon interference visibility, single photon interference visibility, and coupler ratios. (c) Experimentally achieved truth table. (d) Success probability as a function of two photon interference visibility for the input states (blue), input states (red), and averaged over all input states (green). Solid lines are for an ideal circuit and dashed lines are for the circuit realized experimentally. The values extracted from the measured truth table are shown as black squares, error bars are Poissonian errors in the number of counts.
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