Molecular Assembly of Ground-State Cooled Single Atoms

Abstract

We demonstrate full quantum state control of two species of single atoms using optical tweezers and assemble the atoms into a molecule. Our demonstration includes 3D ground-state cooling of a single atom (Cs) in an optical tweezer, transport by several microns with minimal heating, and merging with a single Na atom. Subsequently, both atoms occupy the simultaneous motional ground state with 61(4)% probability. This realizes a sample of exactly two co-trapped atoms near the phase-space-density limit of one, and allows for efficient stimulated-Raman transfer of a pair of atoms into a molecular bound state of the triplet electronic ground potential a 3 Σ + . The results are key steps toward coherent creation of single ultracold molecules, for future exploration of quantum simulation and quantum information processing.

Ultracold polar molecules as qudits

“…Molecules in 2 Σ states possess an unpaired electron, whereas those in 1 Σ states do not. 1 Σ is the electronic ground state of molecules formed by associating two alkali atoms [39][40][41][42][43][44][45][46][47][48][49]. S 2 is the electronic ground state of molecules such as SrF [50], CaF [51,52], YbF [78] and YO [53], which have been recently laser cooled.…”

“…This will lead to differences in the resonant frequencies for molecules in different motional states. However, recent experiments [49,97,98] have succeeded in cooling atoms to their motional ground-state with a probability of greater than 0.990. We believe that such techniques can be extended to molecules and will reduce gate errors to below 1%.…”

“…The rotational and spin degrees of freedom make it possible to encode quantum information in ways not possible on other platforms. Experiments with ultracold molecules have progressed rapidly over the last decade [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53], and the rotational, fine and hyperfine structure has been studied in detail [54][55][56][57][58][59][60][61]. Heteronuclear molecules can have electric dipole moments fixed in the molecular frame, allowing manipulation of the quantum states with microwave fields [57][58][59]62].…”

“…We consider ultracold molecules trapped in the motional ground states of optical tweezers. Tweezers are an established tool for atoms [70][71][72][73][74][75], and have recently been extended to ultracold molecules, both by loading laser-cooled molecules directly into tweezers [76] and by associating atoms in a tweezer to form molecules [48,49]. Tweezers offer single-particle addressability and detection, combined with easy scaling up to arrays of ∼100 traps [73][74][75], making them an ideal platform for quantum computation with ultracold molecules.…”

Encoding a qubit in a molecule

“…Laser cooling and trapping techniques have recently enabled several seminal advances for diatomic polar molecules, namely: the creation of low-entropy arrays in an optical lattice [39,40], trapping and imaging in tweezer arrays [7,9] and magnetic traps [41,42], and even the first quantum degenerate gas of polar molecules [43]. Coherence times of ∼ 100 ms to ∼ 1 second in angular momentum states of diatomic polar molecules have already been observed in several experiments [44][45][46].…”