Cavity-enhanced coherent light scattering from a quantum dot.

The generation of coherent and indistinguishable single photons is a critical step for photonic quantum technologies in information processing and metrology. A promising system is the resonant optical excitation of solid-state emitters embedded in wavelength-scale three-dimensional cavities. However, the challenge here is to reject the unwanted excitation to a level below the quantum signal. We demonstrate this using coherent photon scattering from a quantum dot in a micropillar. The cavity is shown to enhance the fraction of light that is resonantly scattered toward unity, generating antibunched indistinguishable photons that are 16 times narrower than the time-bandwidth limit, even when the transition is near saturation. Finally, deterministic excitation is used to create two-photon N00N states with which we make superresolving phase measurements in a photonic circuit.

In-plane single-photon emission from a L3 cavity coupled to a photonic crystal waveguide.

We report on the design and experimental demonstration of a system based on an L3 cavity coupled to a photonic crystal waveguide for in-plane single-photon emission. A theoretical and experimental investigation for all the cavity modes within the photonic bandgap is presented for stand-alone L3 cavity structures. We provide a detailed discussion supported by finite-difference time-domain calculations of the evanescent coupling of an L3 cavity to a photonic crystal waveguide for on-chip single-photon transmission. Such a system is demonstrated experimentally by the in-plane transmission of quantum light from an InAs quantum dot coupled to the L3 cavity mode.

Narrow emission linewidths of positioned InAs quantum dots grown on pre-patterned GaAs(100) substrates.

We report photoluminescence measurements on a single layer of site-controlled InAs quantum dots (QDs) grown by molecular beam epitaxy (MBE) on pre-patterned GaAs(100) substrates with a 15 nm re-growth buffer separating the dots from the re-growth interface. A process for cleaning the re-growth interface allows us to measure single dot emission linewidths of 80 µeV under non-resonant optical excitation, similar to that observed for self-assembled QDs. The dots reveal excitonic transitions confirmed by power dependence and fine structure splitting measurements. The emission wavelengths are stable, which indicates the absence of a fluctuating charge background in the sample and confirms the cleanliness of the re-growth interface.