Quantum photonics based on solid-state quantum system

Abstract

Excitons in nano-sized semiconductors show interesting optical and electrical properties. Especially when they are in three-dimensionally confined quantum structures, i.e, quantum dots, they behave like artificial atoms. Single excitons in solid-state quantum structures can provide a source of single photons, and the multiple exciton complex such as biexciton or charged exciton are useful to realize entangled photon pairs and spin qubits. Recently there have been a number of studies that integrate these solid-state quantum emitters to various photonic structures and demonstrate bright single photon sources, cavity quantum electrodynamics, non-linear quantum switch, and quantum simulators. Although the semiconductor quantum dots have a strong potential for the applications in quantum information science, the randomness in their frequency and position, and strong interaction with the environment which limits them to be used for practical applications since the most quantum information processing require multiple qubits with long coherence time. Here, I present recent research on quantum dots in a photonic crystal structure for quantum photonics applications. Quantum dots, engineered electronic band structures, are able to generate quantum light, and the photonic crystal, engineered photonic band structures can enhance the brightness and spontaneous emission rate of the coupled emitters. To overcome randomness we developed a local engineering technique that enables multiple, identical quantum dots on-a-chip. As a result, we successfully demonstrate two-photon interference measurements between single photons from separated quantum dots and super-radiant emission between two quantum dots on a waveguide. Our approaches, therefore, pave the way for the scalable, controllable quantum devices involving multiple, identical quantum emitters on a chip.