A Two-Qubit Quantum Gate with

Neutral Atoms in an Optical Lattice

 

Benjamin L. Brown, Marco Anderlini, Patricia J. Lee, Jennifer Sebby-Strabley,

William D. Phillips, and Trey Porto

 

Proposed quantum computing protocols rely on the abilities to prepare the quantum system in any state of the computation basis (“qubit” states) and perform quantum logical operations (“gates”) between pairs of qubits.  We have demonstrated precise control of the physical processes required to implement a two-qubit gate for ultracold neutral atoms in an optical lattice.  The internal spin states of the atom are used as the computation basis.

We employ a novel optical lattice whose unit cell is a double-well.  The shape of the double-well—the height of the barrier between the two wells and their relative depth—is arbitrarily controllable, allowing us to manipulate the motion of the atoms within each double-well.  An additional inherent feature of the double-well is a spin-dependence that causes atoms in different spin states to experience a slightly different potential on one site of each double-well.  This trait allows us to spectroscopically resolve spin-flip transitions at neighboring sites within a double-well, and thus achieve selective preparation of the internal quantum state of the atoms in each side of the double-well.  Combining this technique with our ability to manipulate the topology of the double-well, we induce spin-dependent motion, resulting in spatial separation of different spin states.  We induce a further topological manipulation that fuses adjacent double-well sites into single wells, initiating collisions between pairs of atoms in different spin states trapped in neighboring sites of the double-well optical lattice.  We control and observe coherent spin-exchange interactions between these pairs of atoms, demonstrating the possibility of realizing a two-qubit square-root-of-swap gate for optically trapped neutral atoms.

 

 

Postdocs:      Ben Brown, Marco Anderlini, Patty Lee, Jenni Sebby-Strabley

Submitter:      Ben Brown

Mentor:         Trey Porto

Division:        Atomic Physics (842)

Laboratory:   Physics

Building:        216

Room:           B249

Mail Stop:     8424

Telephone:     301-975-4841

Fax:               301-975-8272

Email:            ben.brown@nist.gov

Sigma Xi:       none are members

Category:      Physics