Nanophotonic quantum interface for a single solid-state spin

Abstract

The ability to store and transmit quantum information plays a central role in virtually all quantum information processing applications. Single spins serve as pristine quantum memories whereas photons are ideal carriers of quantum information. Strong interactions between these two systems provide the necessary interface for developing future quantum networks and distributed quantum computers. They also enable a broad range of critical quantum information functionalities such as entanglement distribution, non-destructive quantum measurements and strong photon-photon interactions. Realizing spin-photon interactions in a solid-state device is particularly desirable because it opens up the possibility of chip-integrated quantum circuits that support gigahertz bandwidth operation.

In this thesis, I demonstrate a nanophotonic quantum interface between a single solid-state spin and a photon, and explore its applications in quantum information processing. First, we experimentally realize a spin-photon quantum phase switch based on a strongly coupled quantum dot and photonic crystal cavity system. This device enables coherent light-matter interactions at the fundamental limit, where a single spin controls the polarization of a photon and a single photon flips the spin state. Furthermore, we theoretically propose a way to deterministically generate spin-photon entanglement based on the spin-photon quantum interface, which is an important step towards solid-state implementations of quantum repeaters and quantum networks. Next, we show both theoretically and experimentally, a new method to optically read out a solid-state spin based on the same cavity quantum electrodynamics (QED) system. This new method achieves significant improvement in spin readout fidelity over typical approaches using fluorescence light detection.

In the end, we report efforts to realize tunable and robust quantum dot based cavity QED systems. We present a technique for tuning the frequency of a quantum dot that is strongly coupled to a photonic crystal cavity by applying strain. This tuning technique enables us to accurately control the detuning between a quantum dot and a cavity without affecting other emission properties of the dot, which is essential for lots of applications associated with cavity QED systems, including non-classical light generation, photon blockade, single photon level optical switch, and also our major focus, the spin-photon quantum interface.