Focus: Atomic Steps in Motion

It was recently shown that a single atom can efficiently scatter photons out of a focused coherent light beam [1, 2, 3]. The scattering probability is strongly dependent on a thermal motion of the atom and can be maximized if the atom is well localized at a focus. To achieve that, we implement a Raman sideband cooling technique that is commonly used in ion traps [4]. Our trap, formed by focused Gaussian light beam at 980nm, has characteristic frequencies of ντ= 55 kHz and νl= 7 kHz corresponding to transverse and longitudinal confinements. A single87Rb atom is loaded into the trap from an optical molasses. Two Raman beams couple the motional states of |F = 2〉 and |F = 1〉 manifolds with a Lamb-Dicke parameter η = 0.084 (Figure 1). The Raman beams are oriented such that momentum transfer occurs only along the strong confinement of the trap with ντ= 55 kHz. The cooling sequence consists of following steps: (1) initial preparation of the atom in |F = 2,mF= −2〉 Zeeman state, (2) Raman transfer between the motional states |F = 2,mF= −2,N〉 and |F = 1,mF= −1,N − 1〉. (3) recycling the atomic population back to |F = 2,mF= −2〉 state via an optical pulse resonant to |5P3/2, F = 2〉 state thus removing a phonon via spontaneous emission.It was recently shown that a single atom can efficiently scatter photons out of a focused coherent light beam [1, 2, 3]. The scattering probability is strongly dependent on a thermal motion of the atom and can be maximized if the atom is well localized at a focus. To achieve that, we implement a Raman sideband cooling technique that is commonly used in ion traps [4]. Our trap, formed by focused Gaussian light beam at 980nm, has characteristic frequencies of ντ= 55 kHz and νl= 7 kHz corresponding to transverse and longitudinal confinements. A single87Rb atom is loaded into the trap from an optical molasses. Two Raman beams couple the motional states of |F = 2〉 and |F = 1〉 manifolds with a Lamb-Dicke parameter η = 0.084 (Figure 1). The Raman beams are oriented such that momentum transfer occurs only along the strong confinement of the trap with ντ= 55 kHz. The cooling sequence consists of following steps: (1) initial preparation of the atom in |F = 2,mF= −2〉 Zeeman state, (2) Raman transfer between the motional states |F = 2,mF= −2,N〉 and |F = 1,mF= −1,N − 1〉. (3) recycling the atomic population back to |F = 2,mF= −2〉 state via an optical pulse resonant to |5P3/2, F = 2〉 state thus removing a phonon via spontaneous emission.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)May 1, 20110 citations

Atomic Motion

Gunther K. Wertheim

Elsevier eBooksJan 1, 19647 citations

Molecular heat pump for rotational states

Constantinos Lazarou, Matthias Keller, B. M. Garraway

In this work, we investigate the theory for three different unidirectional population-transfer schemes in trapped multilevel systems which can be utilized to cool molecular ions. The approach we use exploits the laser-induced coupling between the internal and motional degrees of freedom so that the internal state of a molecule can be mapped onto the motion of that molecule in an external trapping potential. By sympathetically cooling the translational motion back into its ground state, the mapping process can be employed as part of a cooling scheme for molecular rotational levels. This step is achieved through a common mode involving a laser-cooled atom trapped alongside the molecule. For the coherent mapping, we will focus on adiabatic passage techniques which may be expected to provide robust and efficient population transfers. By applying far-detuned chirped adiabatic rapid passage pulses, we are able to achieve an efficiency of better than $98%$ for realistic parameters and including spontaneous emission. Even though our main focus is on cooling molecular states, the analysis of the different adiabatic methods has general features which can be applied to atomic systems.In this work, we investigate the theory for three different unidirectional population-transfer schemes in trapped multilevel systems which can be utilized to cool molecular ions. The approach we use exploits the laser-induced coupling between the internal and motional degrees of freedom so that the internal state of a molecule can be mapped onto the motion of that molecule in an external trapping potential. By sympathetically cooling the translational motion back into its ground state, the mapping process can be employed as part of a cooling scheme for molecular rotational levels. This step is achieved through a common mode involving a laser-cooled atom trapped alongside the molecule. For the coherent mapping, we will focus on adiabatic passage techniques which may be expected to provide robust and efficient population transfers. By applying far-detuned chirped adiabatic rapid passage pulses, we are able to achieve an efficiency of better than $98%$ for realistic parameters and including spontaneous emission. Even though our main focus is on cooling molecular states, the analysis of the different adiabatic methods has general features which can be applied to atomic systems.

arXiv:1001.4394Physical Review AJan 27, 20109 citations

Focus: Reflections of an Atom

Corinna Wu

Aug 1, 20060 citations

Motion of a Bose–Einstein Condensate Bright Soliton Incident on a Step-Like Potential

Cheng Yong-Shan, Gong Rong-zhou, Hong Li

The motion characteristics of a Bose–Einstein condensate bright soliton incident on a local step-like potential barrier are investigated analytically by means of the variational approach. The dynamics of the soliton-potential interaction is studied as well. Then the results are verified by direct numerical simulations of the Gross–Pitaevskii equation. It is found that a moving bright soliton can be reflected from or pass over a step-like potential in a controllable fashion, the critical velocity depends on the width of the soliton and the parameters of the step, and the motion trajectory of the soliton does not depend on its phase. The atom density envelope of the soliton is changed as the result of the interaction between the soliton and the step-like potential.The motion characteristics of a Bose–Einstein condensate bright soliton incident on a local step-like potential barrier are investigated analytically by means of the variational approach. The dynamics of the soliton-potential interaction is studied as well. Then the results are verified by direct numerical simulations of the Gross–Pitaevskii equation. It is found that a moving bright soliton can be reflected from or pass over a step-like potential in a controllable fashion, the critical velocity depends on the width of the soliton and the parameters of the step, and the motion trajectory of the soliton does not depend on its phase. The atom density envelope of the soliton is changed as the result of the interaction between the soliton and the step-like potential.

Chinese Physics LettersJan 1, 20077 citations

98%

for realistic parameters and including spontaneous emission. Even though our main focus is on cooling molecular states, the analysis of the different adiabatic methods has general features which can be applied to atomic systems.