Radiofrequency-dressed-state potentials for neutral atoms

Abstract

Potentials for atoms can be created by external fields acting on properties like magnetic moment, charge, polarizability, or by oscillating fields which couple internal states. The most prominent realization of the latter is the optical dipole potential formed by coupling ground and electronically excited states of an atom with light. Here we present an experimental investigation of the remarkable properties of potentials derived from radio-frequency (RF) coupling between electronic ground states. The coupling is magnetic and the vector character allows to design state dependent potential landscapes. On atom chips this enables robust coherent atom manipulation on much smaller spatial scales than possible with static fields alone. We find no additional heating or collisional loss up to densities approaching 10 15 atoms / cm 3 compared to static magnetic traps. We demonstrate the creation of Bose-Einstein condensates in RF potentials and investigate the difference in the interference between two independently created and two coherently split condensates in identical traps. All together this makes RF dressing a powerful new tool for micro manipulation of atomic and molecular systems. Dressing of internal states of an atom with an external field is a well known technique in quantum optics [1]. The coupling of atomic states to an oscillating field leads to new eigenstates and eigenenergies in the combined system. These dressed states can form adiabatic potentials, which can be employed for atom trapping and manipulation. The most prominent example is the optical dipole potential [2] created when intense coherent light couples ground and electronically excited states of an atom. To create conservative potentials for coherent manipulation spontaneous relaxation of the excited state has to be avoided and hence the light field has to be far detuned. Consequently the magnitude and shape of the dipole potential is given by the local intensity of the light field. Such far detuned dipole potentials are widely used in ultra cold atom experiments [3].Dressing can also be achieved by coupling hyperfine components of the electronic ground state by a magnetic radio-frequency (RF) or micro-wave (MW) field. Dressed state potentials resulting from RF coupling of two spin states in a magnetic field have been studied in neutron optics [4]. Adiabatic potentials induced by coupling hyperfine states with a micro wave have been proposed in Ref. [5], and a detuned micro-wave has been used for trapping ultra cold Cs atoms [6]. The trapping of neutral atoms with RF induced potentials was proposed in [7] and first demonstrated for thermal Rb atoms [8]. Recently RF dressed state potentials were employed for coherent splitting of a one-dimensional Bose-Einstein condensate and matter-wave interference [9]. In this paper, we give for the first time a full experimental demonstra- * Electronic address: hofferberth@atomchip.org tion and analysis of the remarkable properties of these adiabatic RF dressed state potentials, which make them a versatile ...

Mean-field dynamics of a Bose Josephson junction in an optical cavity

“…This extends our previous work to the many-atom case [7]. The system may be constructed by splitting a Bose Einstein condensate, which already couples to a single cavity mode, into two weakly linked condensates, as can be done in various ways [8,9,10,11,12]. We restrict to the large detuning and low excitation limit, so that the atomic spontaneous emission can be neglected.…”

RF spectroscopy in a resonant RF-dressed trap

“…In the case of a non-resonant RF trap, this scheme was used to prepare independent condensates in a double well [11]. In this paper, we present results of spectroscopy in the dressed trap, obtained by recording the atom losses induced by a very weak second RF field [15,16].…”

“…In this case, denoted here as the 'off-resonant configuration', the detuning of the RF field to the magnetic Zeeman splitting is negative everywhere and the atoms are expelled from the most resonant central region, leading for example to a double well structure well suited for matter wave interferometry [11]. On the other hand, the trapping potential may be due essentially to the variation of the detuning, the atoms being then attracted towards the regions of zero detuning [1].…”

OCTBEC—A Matlab toolbox for optimal quantum control of Bose–Einstein condensates

“…In the vast majority of these schemes the wavefunction of the BoseEinstein condensate, trapped in the vicinity of an atom chip [17], is manipulated through variation of the magnetic confinement potential. This is achieved by changing the currents through the gate wires mounted on the chip or modifying the strength of additional radio-frequency fields [5,[18][19][20][21]. These external, timedependent parameters thus provide a versatile control for wavefunction manipulations, and make atom chips attractive candidates for quantum control applications.…”

“…The possibility to store, manipulate [1][2][3][4][5][6], and measure single quantum systems with extremely high precision has initiated great stimulus in various fields of research, ranging from atom interferometry [4,[6][7][8], over quantum gates [9][10][11] and resonant condensate transport [12], to nonlinear atom optics [13][14][15][16]. In the vast majority of these schemes the wavefunction of the BoseEinstein condensate, trapped in the vicinity of an atom chip [17], is manipulated through variation of the magnetic confinement potential.…”