arXiv subjects

Young-Tak Chough

Publications and source records attributed to Young-Tak Chough.

7 recordsLinked to original sources

arXiv2016

Generation of an optical Schrödinger-cat-like state in a non-ideal cavity by injecting opposite-phase atomic dipoles

We propose a method to generate an optical Schrödinger-cat-like state in a cavity in a substantial decoherence regime. Even when the cavity decay rate is considerably large, a cat-like state can be generated in a laser-like setting if the gain for the field is larger than the loss. Under the condition that opposite-phase atomic dipoles repeatedly traverse the cavity, the cavity field converges to a squeezed vacuum state in a steady state. A Schrödinger-cat-like state is then generated when a single photon decay occurs. The phase-space distribution of the cat state can be revealed in homodyne detection by using the decaying photon as a herald event. Quantum trajectory simulation was used to identify the conditions for the Schrödinger-cat-like state formation as well as to analyze the properties of those states. Based on these simulations, possible experiments are proposed within the reach of the current technology.

quant-ph↗

arXiv2016

Coherent and Dynamic Beam Splitting based on Light Storage in Cold Atoms

We demonstrate a coherent and dynamic beam splitter based on light storage in cold atoms. An input weak laser pulse is first stored in a cold atom ensemble via electromagnetically-induced transparency (EIT). A set of counter-propagating control fields, applied at a later time, retrieves the stored pulse into two output spatial modes. The high visibility interference between the two output pulses clearly demonstrates that the beam splitting process is coherent. Furthermore, by manipulating the control lasers, it is possible to dynamically control the storage time, the power splitting ratio, the relative phase, and the optical frequencies of the output pulses. The active beam splitter demonstrated in this work is expected to significantly reduce the resource requirement in photonic quantum information and in all-optical information processing as a single cold atom ensemble can functionally replace a variety of optical elements, including beam splitters, mirrors, phase shifters, and optical quantum memories.

quant-ph↗

arXiv2014

Quantum coherence and population transfer in a driven cascade three-level artificial atom

We present an experimental investigation on the spectral characteristics of an artificial atom "transmon qubit" constituting a three-level cascade system (Ξ-system) in the presence of a pair of external driving fields. We observe two different types of Autler-Townes (AT) splitting: type I, where the phenomenon of two-photon resonance tends to diminish as the coupling field strength increases, and type II, where this phenomenon mostly stays constant. We find that the types are determined by the cooperative effect of the decay rates and the field strengths. Theoretically analyzing the density-matrix elements in the weak-field limit where the AT effect is suppressed, we single out events of pure two-photon coherence occurring owing to constructive quantum interference.

cond-mat.supr-con↗

arXiv2009

Atomic Solc filter: multi-resonant photoemission via periodic poling of atom-cavity coupling constant

This paper describes a novel atom-cavity interaction induced by periodically poled atom-cavity coupling constant which leads to multiple narrow photoemission bands for an initially inverted two-level atom under the strong coupling condition. The emission bandpass narrowing has a close analogy with the folded Solc filter in the context of quasi-phase matching by periodic poling. We present a closed form solution of the emission probability at the end of interaction and deduce the multiple phase matching condition for this system which is programmable by the interaction time. The Bloch sphere analysis provides a clear understanding of the underlying atomic dynamics associated with the multiple resonances in the semiclassical limit. Furthermore, we show that this interaction can be applied to generation of the nonclassical field with sub-Poisson photon statistics.

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

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↗

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↗