title: Entangling two transportable neutral atoms via local spin exchange.
abstract: To advance quantum information science, physical systems are sought that meet the stringent requirements for creating and preserving quantum entanglement. In atomic physics, robust two-qubit entanglement is typically achieved by strong, long-range interactions in the form of either Coulomb interactions between ions or dipolar interactions between Rydberg atoms. Although such interactions allow fast quantum gates, the interacting atoms must overcome the associated coupling to the environment and cross-talk among qubits. Local interactions, such as those requiring substantial wavefunction overlap, can alleviate these detrimental effects; however, such interactions present a new challenge: to distribute entanglement, qubits must be transported, merged for interaction, and then isolated for storage and subsequent operations. Here we show how, using a mobile optical tweezer, it is possible to prepare and locally entangle two ultracold neutral atoms, and then separate them while preserving their entanglement. Ground-state neutral atom experiments have measured dynamics consistent with spin entanglement, and have detected entanglement with macroscopic observables; we are now able to demonstrate position-resolved two-particle coherence via application of a local gradient and parity measurements. This new entanglement-verification protocol could be applied to arbitrary spin-entangled states of spatially separated atoms. The local entangling operation is achieved via spin-exchange interactions, and quantum tunnelling is used to combine and separate atoms. These techniques provide a framework for dynamically entangling remote qubits via local operations within a large-scale quantum register.
authors.affiliation: JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309, USA.|Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Kaufman
authors.affiliation: JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309, USA.|Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
authors.forename: B J
authors.initials: BJ
authors.lastname: Lester
authors.affiliation: Joint Quantum Institute and the National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: M
authors.initials: M
authors.lastname: Foss-Feig
authors.affiliation: JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Wall
authors.affiliation: JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309, USA.|Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Rey
authors.affiliation: JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309, USA.|Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Regal