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arXiv:2202.04813 · Physica Scripta

Atom walking in a traveling-wave light

Wenxi Lai

Published Mar 2, 2023• 1 citation
arXivHTMLPDF

Abstract

Abstract In this paper, we investigate mechanical motion of ultra-slow single atoms considering each atom is coherently coupled to a traveling-wave light. The main noise in this system is originated from Doppler broadening due to the continuous momentum distribution in atom wave packet. Here, it is proved that the Doppler broadening could be effectively suppressed in strong coupling regime. Under the coherent coupling, individual neutral atoms periodically walk in a definite direction. Direction of the motion depends on occupation of the atom in its two internal states related to the optical transition, since the atom would be affected by attractive or repulsive forces depending on the internal states. It is analogous to the electric force acting on negatively or positively charged particles. We explain them with spin–orbit coupling of atoms which is hidden in our Hamiltonian. These results have potential applications for the construction of future atomic devices.

DOI
10.1088/1402-4896/acc0ad

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Abstract In this paper, we investigate mechanical motion of ultra-slow single atoms considering each atom is coherently coupled to a traveling-wave light. The main noise in this system is originated from Doppler broadening due to the continuous momentum distribution in atom wave packet. Here, it is proved that the Doppler broadening could be effectively suppressed in strong coupling regime. Under the coherent coupling, individual neutral atoms periodically walk in a definite direction. Direction of the motion depends on occupation of the atom in its two internal states related to the optical transition, since the atom would be affected by attractive or repulsive forces depending on the internal states. It is analogous to the electric force acting on negatively or positively charged particles. We explain them with spin–orbit coupling of atoms which is hidden in our Hamiltonian. These results have potential applications for the construction of future atomic devices.
Abstract In this paper, we propose a simplified model of the optical Stern–Gerlach effect based on coherent coupling between the clock transition of alkaline-earth single atoms and a traveling-wave light. It is demonstrated that spin–orbit coupling-induced chiral motion in atom deflection appears under strong atom–light interaction. The strong optical driving removes the perturbation from the Doppler effect and back-action effect to access the coherent system. In this process, the superposition of distant matter waves connected to the arbitrary distribution of the atom internal state could be predicted, which is important for the realization of atom interferometry and quantum-state operation. The influence of atom relaxation and atom–atom interactions is discussed. The basic conditions for the experimental design are given at the end of this work.
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We investigate the diffraction of a three-level atom from a "walking" light wave composed of counterpropagating traveling waves of different frequencies. The coupling of the two nondegenerate internal ground states by means of an off-resonant Raman transition resonantly couples the initial external momentum state to only one other momentum state. This happens even in the Raman-Nath regime, where the interaction time is short enough that momentum transfer is not constrained by phase-matching conditions. The final momentum state depends on the initial internal state of the atom and the relative directions of the two traveling waves. By using multiple diffraction regions, this process can be used to coherently split a beam of atoms into two beams that are widely separated in momentum space. This type of beam splitter would be useful in the building an atom interferometer.
An optical method for precise purification of chemical elements is introduced in this paper. The materials are supposed to be in the states of gaseous beams, which are coherently coupled to an external traveling light during purification. Before decoherence occurs, atoms periodically move in the light with different speeds that depends on masses and optical transition wave lengths of these atoms. The speed gradient leads to deflections of different atoms in different directions. The model is described by Schrödinger equations with analytical results. This method could be used for some hardly separable atoms and isotopes depending on the condition of atom coherent time. The present work opens a platform for applications of cold atom technology in the purification of atoms and molecules.
A semiclassical model of the force and momentum diffusion on a point particle is used to describe the motion of a two-level atom strongly coupled to a single Gaussian cavity mode. The effects of the momentum diffusion on the motion of an atom in a cavity are investigated in a regime similar to that of the experiment performed by Mabuchi et al. [Opt. Lett. 21, 1393 (1996)]. It is found that a slow atom quickly develops significant velocities along the cavity axis. The limited bandwidth in the experiment of Mabuchi et al. means that the full intensity signal due to atomic motion in the standing wave is filtered leading to the apparently smaller velocities observed. It is shown that a negative detuning of the laser and cavity from the atomic resonance would lead to nonzero dipole forces and significantly reduced velocities along the standing wave. An analysis of the intensity signal with a larger bandwidth is proposed, which would track the velocity of the atom along the cavity axis. These results are compared with a Monte Carlo wave-function simulation similar to that used to treat Doppler cooling.
In this paper we consider the effects of spontaneous emission on the problem of atomic reflection from an optical evanescent travelling wave. The atoms are assumed to be travelling so slowly that the external degrees of freedom of the atom need to be treated quantum mechanically. Spontaneous emission is modelled using a fully quantum mechanical model based on the quantum Monte Carlo technique which includes the effects of atomic recoil. The results of the simulation are compared with a semi-classical Monte Carlo simulation in which the atomic motion is treated classically and the internal state of the atom is assumed to follow the light-induced quasipotentials adiabatically between spontaneous emission events. The spontaneous emission leads to a broadening of the momentum distribution of the outgoing wave packet and mechanisms for this broadening are discussed.