The Nobel Prize in physics 2012 was awarded “for ground-breaking experimental methods that enable measuring and manipulation of individual quantum systems”. The methods are based on optical technologies such as a laser, and will open a door to new quantum technologies in which light and matter interact in a qualitatively different manner.

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The 2012 Nobel Prize in Physics was awarded to Serge Haroche and David J. Wineland for their groundbreaking work in developing experimental methods that measure and manipulate individual quantum systems. Their methods, which have allowed the control of a system constituted of a single atom (ion) and a single photon, have opened a wide variety of applications. As a tutorial, this article outlines the fundamental concept of their Nobel-awarded methods: cavity quantum electrodynamics.

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Our recent advances in solid-state cavity quantum electrodynamics (CQED) and lasing oscillation in single quantum dot (QD)-photonic crystal (PhC) nanocavity coupled systems are discussed. These include the fabrication of high quality two-dimensional PhC nanocavities, which enable the generation of spontaneous two photon emission from a single QD, and the realization of lasing oscillation with single QD gain in the strong coupling regime. Moreover, CQED in a one-dimensional PhC nanobeam cavity is discussed.

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Theoretical study on entangled photon generation from a quantum dot (QD) embedded in microcavity is briefly reviewed within a strong coupling regime. In this system, entangled photon pairs can be generated through the cascade photon emission via dressed states in the cavity quantum electrodynamics (CQED). Excitation levels of a QD are modeled by a V-type three-level system and four-level system including a biexciton. In contrast to the entangled-photon generation until now, all four Bell states can be generated from an identical cavity system by simply selecting applied-field polarizations and frequencies as characteristic features of the CQED. The CQED effects play a crucial role in providing a high degree of entanglement: (i) spectral fi ltering can be used to extract entangled photons due to the vacuum Rabi splitting and (ii) non-entangled co-polarized photons are strongly suppressed due to the photon blockade effect.

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We review recent progress in the application of whispering-gallery mode microresonators, such as microspheres, microdisks, and microtoroids, in cavity Quantum Electrodynamics (QED). Particular emphasis is made on the studies on the interaction of laser-cooled single atoms with evanescent fi eld of monolithic microtoroidal resonators effi ciently coupled to tapered optical fi bers.

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Circuit quantum electrodynamics is a radical extension of cavity quantum electrodynamics into superconducting electrical circuits, where macroscopic artifi cial atoms with anharmonicity, based on the nonlinearity of Josephson junctions, are strongly coupled to harmonic oscillators. We review the basic concept and recent progress.

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We review the recent developments towards strong coupling of a single ion in cavity QED, in particular by using optical fiber cavities. We also summarize our efforts along the same line being pursued at Sussex University. The main issue in cavity QED with trapped ions has been the incompatibility of dielectric mirrors in trapping potentials. As consequence the mirrors of a cavity have to be further retracted from the ion, rendering the cavity volume rather big to sacrifice the ion-cavity coupling. However, the emerging fiber cavity technology is expected to largely mitigate this difficulty and yet achieve excellent resonator-quality. Achieving strong coupling with single trapped ions enables one to build a highly reliable and controllable quantum interface between matter and light to be used in quantum network. It could also open up new possibilities such as manipulating photonic quantum states via the quantum computing toolbox of ion trap.

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This paper presents an overview of the Al+ optical clock, which is based on quantum logic spectroscopy and provides the most accurate frequency measurement ever reported. Dehmelt’s original design of the optical clock was not realized due to the difficulty in generating the vacuum ultraviolet radiation necessary for laser cooling and the ion’s quantum state detection. The problem was solved by sympathetically cooling the ion with another ion and detecting the quantum state using the ancillary ion. The method, which is called quantum logic spectroscopy, comes from the use of phonon qubit as a bus of the quantum state of the ions in the Cirac-Zoller ion-trap quantum computer. The clock can be simplifi ed by introducing direct excitation by vacuum ultraviolet radiation or another ion species. The clock’s stability will be improved more than ten times by a middle-term stabilized clock laser.

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Argon-fluoride (ArF) excimer laser operations at high repetition rates have been studied with special focus on the distance between electrodes. We find that, for stable laser operations, the maximum repetition rate increases with decreasing electrode separations. This is mainly caused by narrow discharge widths and an electric field intensity distribution that concentrates on the center. For an electrode separation of 8 mm, a homogeneous discharge could be maintained for an ArF excimer laser at a maximum repetition rate of 10 kHz. Results are discussed in detail with special focus on the influence of gas density depletion.

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With the increase of laser equipment and heightening of its power, opportunity of laser exposure to human tissue is also increasing. As well as the other accidents, an accident of the laser takes place in where we did not expect. What are the safe and effective measures to prevent the accident, which is deeply involved with the characteristics of laser? We, as a manufacturer of protective equipment, would mention our attitude to safety measures and the importance of safety glasses.

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