arXiv subjects

Kyungwon An

Publications and source records attributed to Kyungwon An.

49 records · Page 3Linked to original sources

arXiv2006

A definitive number of atoms on demand: controlling the number of atoms in a-few-atom magneto-optical trap

A few 85Rb atoms were trapped in a micron-size magneto-optical trap with a high quadrupole magnetic-field gradient and the number of atoms was precisely controlled by suppressing stochastic loading and loss events via real-time feedback on the magnetic field gradient. The measured occupation probability of single atom was as high as 99%. Atoms up to five were also trapped with high occupation probabilities. The present technique could be used to make a deterministic atom source.

physics.atom-ph↗

arXiv2006

Lineshape measurement of an extreme-weak amplitude-fluctuating light source by the photon-counting-based second-order correlation spectroscopy

We demonstrate lineshape measurement of an extreme-weak amplitude fluctuating light source by using the photon-counting-based second-order correlation spectroscopy combined with the heterodyne technique. The amplitude fluctuation of a finite bandwidth introduces a low-lying spectral structure in the lineshape and thus its effect can be isolated from that of the phase fluctuation. Our technique provides extreme sensitivity suited for single-atom-level applications.

physics.optics↗

arXiv2006

Analysis on the effect of technical fluctuations on laser lineshape

We analyze theoretically the effect of technical fluctuations on laser lineshape in terms of statistics of amplitude and phase noise and their respective bandwidths. While the phase noise tends to broaden the linewidth as the magnitude of the noise increases, the amplitude noise brings out an additional structure with its spectral density reflecting the magnitude of the noise. The effect of possible coupling between those two noises is also discussed.

physics.optics↗

arXiv2006

Regular Spectra and Universal Directionality of Emitted Radiation from a Quadrupolar Deformed Microcavity

We have investigated quasi-eigenmodes of a quadrupolar deformed microcavity by extensive numerical calculations. The spectral structure is found to be quite regular, which can be explained on the basis of the fact that the microcavity is an open system. The far-field emission directions of the modes show unexpected similarity irrespective of their distinct shapes in phase space. This universal directionality is ascribed to the influence from the geometry of the unstable manifolds in the corresponding ray dynamics.

physics.optics↗

arXiv2005

Calibration of second-order correlation functions for non-stationary sources with a multi-start multi-stop time-to-digital converter

A novel high-throughput second-order-correlation measurement system is developed which records and makes use of all the arrival times of photons detected at both start and stop detectors. This system is suitable particularly for a light source having a high photon flux and a long coherence time since it is more efficient than conventional methods by an amount equal to the product of the count rate and the correlation time of the light source. We have used this system in carefully investigating the dead time effects of detectors and photon counters on the second-order correlation function in the two-detector configuration. For a non-stationary light source, distortion of original signal was observed at high photon flux. A systematic way of calibrating the second-order correlation function has been devised by introducing a concept of an effective dead time of the entire measurement system.

physics.ins-det↗

arXiv2005

Observation of sub-Poisson photon statistics in the cavity-QED microlaser

We have measured the second-order correlation function of the cavity-QED microlaser output and observed a transition from photon bunching to antibunching with increasing average number of intracavity atoms. The observed correlation times and the transition from super- to sub-Poisson photon statistics can be well described by gain-loss feedback or enhanced/reduced restoring action against fluctuations in photon number in the context of a quantum microlaser theory and a photon rate equation picture. However, the theory predicts a degree of antibunching several times larger than that observed, which may indicate the inadequacy of its treatment of atomic velocity distributions.

quant-ph↗

arXiv2001

Decoherence-induced wave packet splitting

We provide an intuitive interpretation of the optical Stern-Gerlach effect (OSGE) in the dressed-state point of view. We also analyze the effect of atomic damping in an experiment on the OSGE. We show that the atomic damping also causes the wave packet splitting, in a non-mechanical fashion, as opposed to the coherent process that is mechanical.

quant-ph↗

arXiv2001

An ultrahigh-Q microsphere laser based on the evanescent-wave-coupled gain

We have demonstrated an ultrahigh-Q whispering-gallery-mode (WGM) microsphere laser based on the evanescent-wave-coupled gain. Dye molecules outside the sphere near the equator were excited, resulting in WGM lasing in the lowest radial mode order. The loaded quality factor of the lasing WGM was 8(2)\times 10^9, the highest ever achieved in the microlaser.

physics.optics↗

arXiv2001

Observation of Scarred Modes in Asymmetrically Deformed Microcylinder Lasers

We report observation of lasing in the scarred modes in an asymmetrically deformed microcavity made of liquid jet. The observed scarred modes correspond to morphology-dependent resonance of radial mode order 3 with their Q values in the range of 10^6. Emission directionality is also observed, corresponding to a hexagonal unstable periodic orbit.

physics.optics↗

arXiv2001

Atomic position localization via dual measurement

We study localization of atomic position when a three-level atom interacts with a quantized standing-wave field in the Ramsey interferometer setup. Both the field quadrature amplitude and the atomic internal state are measured to obtain the atomic position information. It is found that this dual measurement scheme produces an interference pattern superimposed on a diffraction-like pattern in the atomic position distribution, where the former pattern originates from the state-selective measurement and the latter from the field measurement. The present scheme results in a better resolution in the position localization than the field-alone measurement schemes. We also discuss the measurement-correlated mechanical action of the standing-wave field on the atom in the light of Popper's test.

quant-ph↗

arXiv2001

Squeezing enhancement by damping in a driven atom-cavity system

In a driven atom-cavity coupled system in which the two-level atom is driven by a classical field, the cavity mode which should be in a coherent state in the absence of its reservoir, can be squeezed by coupling to its reservoir. The squeezing effect is enhanced as the damping rate of the cavity is increased to some extent.

quant-ph↗

arXiv2001

Cavity-damping-induced transitions in a driven atom-cavity system

We investigate the fluorescence spectrum of a two-level atom in a cavity when the atom is driven by a classical field. We show that forbidden dipole transitions in the Jaynes-Cummings Ladder structure are induced in the presence of the cavity damping, which deteriorates the degree of otherwise perfect destructive interference among the transition channels. With the larger cavity decay, these transitions are more enhanced.

quant-ph↗

arXiv2000

Quantum Zeno Effect in Quantum Chaotic Systems

We analyzed the effect of frequent measurements on the quantum systems that are chaotic in the classical limit. It is shown that the kicked rotator, a well-known example of quantum chaos, is too special to be used as a testing ground for the effects of the repeated measurements. The abrupt change of state vectors by the delta-kick singular interruptions causes a quantum anti-Zeno effect. However, in more realistic systems with interaction potentials of continuous time dependence the quantum Zeno effect prevails.

nlin.CD↗