Quantum dots in cavities have been shown to be very bright sources of indistinguishable single photons. Yet the quantum interference between two bright quantum dot sources, a critical step for photon based quantum computation, has never been investig
ated. Here we report on such a measurement, taking advantage of a deterministic fabrication of the devices. We show that cavity quantum electrodynamics can efficiently improve the quantum interference between remote quantum dot sources: poorly indistinguishable photons can still interfere with good contrast with high quality photons emitted by a source in the strong Purcell regime. Our measurements and calculations show that cavity quantum electrodynamics is a powerful tool for interconnecting several devices.
We present an experimental study on the ignition and decay of a polariton optical parametric oscillator (OPO) in a semiconductor microcavity pillar. The combination of a continuous wave laser pump, under quasi-phase matching conditions, and a non-res
onant, 2 ps-long pulse probe allows us to obtain the full dynamics of the system. The arrival of the probe induces a blue-shift in the polariton emission, bringing the OPO process into resonance with the pump, which triggers the OPO-process. We time-resolve the polariton OPO signal emission for more than 1 nanosecond in both real and momentum-space. We fully characterize the emission of the OPO signal with spectral tomography techniques. Our interpretations are backed up by theoretical simulations based on the 2D coupled Gross-Pitaevskii equation for excitons and photons.
We present a time-resolved photoluminescence (PL) study in real- and momentum-space of a polariton condensate switch in a quasi-1D semiconductor microcavity. The polariton flow across the ridge is gated by excitons inducing a barrier potential due to
repulsive interactions. A study of the device operation dependence on the power of the pulsed gate beam obtains a satisfactory compromise for the ON/OFF-signal ratio and -switching time of the order of 0.3 and $thicksim50$ ps, respectively. The opposite transition is governed by the long-lived gate excitons, consequently the OFF/ON-switching time is $thicksim200$ ps, limiting the overall operation speed of the device to $thicksim3$ GHz. The experimental results are compared to numerical simulations based on a generalized Gross-Pitaevskii equation, taking into account incoherent pumping, decay and energy relaxation within the condensate.
We show that the use of momentum-space optical interferometry, which avoids any spatial overlap between two parts of a macroscopic quantum state, presents a unique way to study coherence phenomena in polariton condensates. In this way, we address the
longstanding question in quantum mechanics: emph{Do two components of a condensate, which have never seen each other, possess a definitive phase?} [P. W. Anderson, emph{Basic Notions of Condensed Matter Physics} (Benjamin, 1984)]. A positive answer to this question is experimentally obtained here for light-matter condensates, created under precise symmetry conditions, in semiconductor microcavities taking advantage of the direct relation between the angle of emission and the in-plane momentum of polaritons.
