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.
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.
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.
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.
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.
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.
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.
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.
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.
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.