Sideband Rabi spectroscopy of finite-temperature trapped Bose gases

Abstract

We use Rabi spectroscopy to explore the low-energy excitation spectrum of a finite-temperature Bose gas of rubidium atoms across the phase transition to a Bose-Einstein condensate (BEC). To record this spectrum, we coherently drive the atomic population between two spin states. A small relative displacement of the spin-specific trapping potentials enables sideband transitions between different motional states. The intrinsic nonlinearity of the motional spectrum, mainly originating from two-body interactions, makes it possible to resolve and address individual excitation lines. Together with sensitive atom counting, this constitutes a feasible technique to count single excited atoms of a BEC and to determine the temperature of nearly pure condensates. As an example, we show that for a nearly pure BEC of N = 800 atoms the first excited state has a population of less than five atoms, corresponding to an upper bound on the temperature of 30 nK.

Simulation of XXZ Spin Models using Sideband Transitions in Trapped Bosonic Gases

“…It is worth mentioning that the suppression of red sideband transitions is related to the dephasing effect generated by the anharmonicity of optical dipole trap, also observed in Ref. [31].…”

Mesoscopic quantum superpositions in bimodal Bose-Einstein condensates: Decoherence and strategies to counteract it

“…This shows that one must have initially a small number of excitations in the system in order to have a fidelity close to 1, hence the stringent requirement on temperature: a temperature of 28 nK. This temperature is close to the range ≈40-30 nK already accessed by direct in situ evaporative cooling [42,43]. It might also be reached by using as a coolant the subnanokelvin gases prepared in very weak traps [44].…”

Multiconfigurational time-dependent Hartree method for bosons with internal degrees of freedom: Theory and composite fragmentation of multicomponent Bose-Einstein condensates

“…The experiment in Ref. [8,20] realizes a Bose-Einstein condensate of atoms with two internal degrees of freedom which is confined in three-dimensional parabolic traps the minima of which have different positions for the two internal states of the atoms. In Ref.…”

“…The capabilities of the derived theory are demonstrated by exhibiting the emergence of fragmentation and correlations in a system with one-body potentials which are dependent on the internal state of the considered particles similar to the experimentally realized one in Refs. [8,20]. A new kind of fragmentation which is qualitatively different from the single-component fragmentation of bosonic systems without internal degrees of freedom is found: composite fragmentation -the system's components maintain their coherence while the coherence between them is lost.…”

“…Here, "general" stands for giving reliable predictions for the many-body physics and correlations of interacting bosons with internal structure for any spatial dimension, any interparticle interaction, and any one-body potential. Most realizations of ultracold bosons with internal degrees of freedom are therefore described with a multi-component Gross-Pitaevskii equation [20][21][22][23][24][25]. In the case of bosonic particles without structure a method which self-consistently incorporates correlations has been devised: the (multi-layer) multiconfigurational time-dependent Hartree for bosons method (MCTDHB) [26,27] ( [28]).…”