Three-Dimensional Trapping of Individual Rydberg Atoms in Ponderomotive Bottle Beam Traps

D. Barredo (1) , V. Lienhard (1) , P. Scholl (1) , S. de Léséleuc (1) , T. Boulier (1) , Antoine Browaeys (1) , Thierry Lahaye (1)

1 Laboratoire Charles Fabry / Optique Quantique

We demonstrate three-dimensional trapping of individual Rydberg atoms in holographic optical bottle beam traps. Starting with cold, ground-state 87 Rb atoms held in standard optical tweezers, we excite them to nS 1=2 , nP 1=2 , or nD 3=2 Rydberg states and transfer them to a hollow trap at 850 nm. For principal quantum numbers 60 ≤ n ≤ 90, the measured trapping time coincides with the Rydberg state lifetime in a 300 K environment. We show that these traps are compatible with quantum information and simulation tasks by performing single qubit microwave Rabi flopping, as well as by measuring the interaction-induced, coherent spin-exchange dynamics between two trapped Rydberg atoms separated by 40 μm. These results will find applications in the realization of high-fidelity quantum simulations and quantum logic operations with Rydberg atoms. Neutral atoms excited to Rydberg states are an attractive platform for scalable quantum simulation and computation [1,2]. The strong, controllable interactions between these states can be used to implement high-fidelity quantum gates, or to engineer various types of spin Hamiltonians difficult to study on classical computers [3]. These ideas have been intensively explored in the last years and several milestones have been achieved [4]. Prominent examples of this progress are the demonstration of strong optical non-linearities [5], single-photon sources [6], conditional phase shifters [7], single-photon transistors [8,9], the experimental realizations of two-qubit gates [10-14], or the quantum simulations of spin models with tens of particles in optical lattices [15-17] and in arrays of optical tweezers [18-21]. In none of the above experiments were the Rydberg atoms trapped. However, controlling the motion of Rydberg atoms during gate operation and in quantum simulations is advantageous, since finite atom temperatures and mechanical forces due to the interactions between the particles ultimately limit quantum state fidelities [4,22] and the available time for coherent dynamics [19,23,24]. Rydberg trapping is also a prerequisite for precision measurements of fundamental constants using circular Rydberg states [25,26] or positronium [27]. To date, clouds of Rydberg atoms have been confined to three-dimensional, millimeter-size regions using static magnetic [28-30] or electric fields [31,32]. In an inhomo-geneous ac electric field that oscillates faster than any internal frequency of the Rydberg atom, the weakly bound Rydberg electron experiences an oscillating force that can be used for trapping of the Rydberg atom [33]. The so-called ponderomotive potential, which is the time-averaged kinetic energy of the nearly free Rydberg electron oscillating in the laser field, is proportional to the light intensity. Therefore, to obtain a 3D trap, one must create a dark region surrounded by light in all directions; since the atom trapping arises mainly from the ponderomotive potential experienced by the electron, such traps can be used to confine Rydberg states whatever their n, l, j, m j quantum numbers. Rydberg atoms have been confined in the tight potentials of ponderomotive optical lattices [33,34], but so far only in one dimension. Here we go beyond those initial demonstrations to show three-dimensional trapping of cold individual Rydberg atoms in micron-size optical potentials [35,36]. We use holography to create bottle beam (BOB) traps [37,38] which are deterministically loaded with single Rydberg atoms. We characterize the depth and trapping frequencies of these traps and observe that the trapping time, for principal quantum numbers in the range 60 ≤ n ≤ 90, is mainly limited by the Rydberg states lifetime in the presence of blackbody radiation at 300 K. Finally, we illustrate the compatibility of these traps with quantum simulation by driving Rabi flopping between different Rydberg states, and by observing the coherent exchange of internal states induced by the dipole-dipole interaction for two atoms confined in BOB traps separated by 40 μm.

Domaines: Physique Atomique [physics.atom-ph]

D. Barredo, V. Lienhard, P. Scholl, S. de Léséleuc, T. Boulier, et al.. Three-Dimensional Trapping of Individual Rydberg Atoms in Ponderomotive Bottle Beam Traps. Physical Review Letters, 2020, 124 (2), ⟨10.1103/PhysRevLett.124.023201⟩. ⟨hal-02444993⟩