Journal Article

Quantum nature of a strongly coupled single quantum dot–cavity system

Winger, M., Atatüre, M., Gulde, S., Fält, S., Imamoğlu, A., Badolato, A., Gerace, D., Hennessy, K., Hu, E. L.

2007

Overview

On quantum nature Cavity quantum electrodynamics (QED) studies the interaction between a quantum emitter (for example an atom or a quantum dot) and a single mode from a radiation field. When the two are strongly coupled it is possible to realize key quantum information processing tasks. In the solid state this could be achieved by coupling semiconductor quantum dots to optical microcavities. However, validating the efficacy of quantum dots in quantum information applications requires confirmation of the quantum nature of the quantum-dot–cavity system in the strong coupling regime. A collaboration between labs at ETH Zurich and the University of California, Santa Barbara, now provides this sought-after confirmation. The experiments involve a photonic crystal nanocavity in which one, and only one, quantum dot is located precisely at the cavity electric field maximum. A series of experiments that provide confirmation of the quantum nature of the quantum–dot–cavity system in the strong coupling regime by studying a photonic crystal nanocavity in which one, and only one, quantum dot is located precisely at the cavity electric field maximum. Cavity quantum electrodynamics (QED) studies the interaction between a quantum emitter and a single radiation-field mode. When an atom is strongly coupled to a cavity mode 1 , 2 , it is possible to realize important quantum information processing tasks, such as controlled coherent coupling and entanglement of distinguishable quantum systems. Realizing these tasks in the solid state is clearly desirable, and coupling semiconductor self-assembled quantum dots to monolithic optical cavities is a promising route to this end. However, validating the efficacy of quantum dots in quantum information applications requires confirmation of the quantum nature of the quantum-dot–cavity system in the strong-coupling regime. Here we find such confirmation by observing quantum correlations in photoluminescence from a photonic crystal nanocavity 3 , 4 , 5 interacting with one, and only one, quantum dot located precisely at the cavity electric field maximum. When off-resonance, photon emission from the cavity mode and quantum-dot excitons is anticorrelated at the level of single quanta, proving that the mode is driven solely by the quantum dot despite an energy mismatch between cavity and excitons. When tuned to resonance, the exciton and cavity enter the strong-coupling regime of cavity QED and the quantum-dot exciton lifetime reduces by a factor of 145. The generated photon stream becomes antibunched, proving that the strongly coupled exciton/photon system is in the quantum regime. Our observations unequivocally show that quantum information tasks are achievable in solid-state cavity QED.

• Publisher: Nature Publishing Group UK,Nature Publishing,Nature Publishing Group
• Subject: Cavitation / Cavity quantum electrodynamics ; micromasers / Classical and quantum physics: mechanics and fields / Correlation analysis / Electric fields / Emissions / Exact sciences and technology / Excitons / Fundamental areas of phenomenology (including applications) / Holes / Humanities and Social Sciences / Joining / letter / multidisciplinary / Nanostructure / Optical materials / Optics / Particle physics / Photonic bandgap materials / Photons / Physics / Quantum dots / Quantum information / Quantum optics / Quantum theory / Resonance / Science / Science (multidisciplinary) / Semiconductors / Tasks