Entangling two transportable neutral atoms via local spin exchange

• Published in: Nature (London) Vol. 527; no. 7577; pp. 208 - 211
• Main Authors: Kaufman, A. M., Lester, B. J., Foss-Feig, M., Wall, M. L., Rey, A. M., Regal, C. A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 12.11.2015; Nature Publishing Group
• Subjects: 639/766/36/1125; 639/766/483/1139; 639/766/483/481; Atoms; Atoms & subatomic particles; Experiments; Humanities and Social Sciences; letter; multidisciplinary; Properties; Quantum dots; Quantum theory; Science; Symmetry
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature16073

Spin-entangled states between two neutral atoms in different optical tweezers are prepared by combining them in the same optical tweezer and allowing for controlled interactions, after which the particles are dynamically separated in space and their entanglement is maintained. Neutral atoms entangled — but separately Neutral atoms in optical tweezers have been identified as promising building blocks for a quantum computer. But a prerequisite for using them in a quantum computing architecture is that entanglement between atoms in different optical tweezers can be generated and maintained. Here, Cindy Regal and colleagues show how to create spin-entangled states between two neutral atoms in different optical tweezers and manage to maintain it even if the tweezers are separated. This implies that entanglement between distant qubits can be generated by local operations, which could become an important technique in quantum information processing. 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 1 , 2 , 3 , 4 . Although such interactions allow fast quantum gates, the interacting atoms must overcome the associated coupling to the environment and cross-talk among qubits 5 , 6 , 7 , 8 . 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 9 , 10 , 11 . Ground-state neutral atom experiments have measured dynamics consistent with spin entanglement 10 , 12 , 13 , and have detected entanglement with macroscopic observables 14 , 15 ; we are now able to demonstrate position-resolved two-particle coherence via application of a local gradient and parity measurements 1 . This new entanglement-verification protocol could be applied to arbitrary spin-entangled states of spatially separated atoms 16 , 17 . The local entangling operation is achieved via spin-exchange interactions 9 , 10 , 11 , 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.