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Hiroki Saito

Publications and source records attributed to Hiroki Saito.

116 records · Page 7Linked to original sources
arXiv2002

Dynamical Casimir effect without boundary conditions

The moving-mirror problem is microscopically formulated without invoking the external boundary conditions. The moving mirrors are described by the quantized matter field interacting with the photon field, forming dynamical cavity polaritons: photons in the cavity are dressed by electrons in the moving mirrors. The effective Hamiltonian for the polariton is derived, and corrections to the results based on the external boundary conditions are discussed.

quant-ph↗
arXiv2001

Mean-field analysis of collapsing and exploding Bose-Einstein condensates

The dynamics of collapsing and exploding trapped Bose-Einstein condensat es caused by a sudden switch of interactions from repulsive to attractive a re studied by numerically integrating the Gross-Pitaevskii equation with atomic loss for an axially symmetric trap. We investigate the decay rate of condensates and the phenomena of bursts and jets of atoms, and compare our results with those of the experiments performed by E. A. Donley {\it et al.} [Nature {\bf 412}, 295 (2001)]. Our study suggests that the condensate decay and the burst production is due to local intermittent implosions in the condensate, and that atomic clouds of bursts and jets are coherent. We also predict nonlinear pattern formation caused by the density instability of attractive condensates.

cond-mat↗
arXiv2000

Intermittent implosion and pattern formation of trapped Bose-Einstein condensates with attractive interaction

The collapsing dynamics of a trapped Bose-Einstein condensate (BEC) with attractive interaction are revealed to exhibit two previously unknown phenomena. During the collapse, BEC undergoes a series of rapid implosions that occur {\it intermittently} within a very small region. When the sign of the interaction is suddenly switched from repulsive to attractive, e.g., by the Feshbach resonance, density fluctuations grow to form various patterns such as a shell structure.

cond-mat↗
arXiv2000

Power laws and collapsing dynamics of a trapped Bose-Einstein condensate with attractive interactions

The critical behavior of collective modes and the collapsing dynamics of trapped Bose-Einstein condensates with attractive interactions are studied analytically and numerically. The time scales of these dynamics both below and above the critical point of the collapse are found to obey power laws with a single parameter of N/N_c - 1, where N is the number of condensate atoms and N_c is the critical number. The collapsing condensate eventually undergoes rapid implosion, which occurs several times intermittently, and then the implosion turns to an explosion. The release energy of the explosion is found to be proportional to the square of the interaction strength, inversely proportional to the three-body recombination rate, and independent of the number of condensate atoms and the trap frequency.

cond-mat↗
arXiv1999

Correlated scattering of photons from a trapped Bose-Einstein condensate

The second-order coherence of photons scattered from a trapped Bose-Einstein condensate is found to be enhanced for the scattering angles that are either the same or symmetrical with respect to the direction of laser propagation. The enhancement occurs periodically with respect to the time interval between photons, and becomes less and less pronounced with increasing the strength of the interaction between atoms.

cond-mat↗
arXiv1999

Number-phase-squeezed few-photon state generated from squeezed atoms

This paper develops a method of manipulating the squeezed atom state to generate a few-photon state whose phase or photon-number fluctuations are prescribed at our disposal. The squeezed atom state is a collective atomic state whose quantum fluctuations in population difference or collective dipole are smaller than those of the coherent atom state. It is shown that the squeezed atom state can be generated by the interaction of atoms with a coherent state of the electromagnetic field, and that it can be used as a tunable source of squeezed radiation. A variety of squeezed states, including the photon-number squeezed state and the phase squeezed state, can be produced by manipulating the atomic state. This is owing to the fact that quantum-statistical information of the atomic state is faithfully transferred to that of the photon state. Possible experimental situations to implement our theory are discussed.

quant-ph↗
arXiv1997

Quantum-Controlled Few-Photon State Generated by Squeezed Atoms

General principles and experimental schemes for generating a desired few-photon state from an aggregate of squeezed atoms are presented. Quantum-statistical information of the collective atomic dipole is found to be faithfully transferred to the photon state even in a few-photon regime. The controllability of few-photon states is shown to increase with increasing the number of squeezed atoms.

quant-ph↗