Southwest Quantum Information and Technology
Fourteenth Annual Meeting, February 16-19, 2012
Albuquerque, New Mexico
Full Program | Thursday | Friday | Saturday | Sunday | All Sessions
| SESSION 10: Neutral Atom QIP - Alvarado "D" | Session Chair: |
| 2:00pm-2:45pm | Antoine Browaeys, Institut Optique, CNRS (invited) | Entanglement of two atoms using the Rydberg Blockade | Abstract. When two quantum systems interact strongly, their simultaneous excitation by the same driving pulse may be forbidden: this is called blockade of excitation. Recently, extensive studies have been devoted to the Rydberg blockade between neutral atoms, which appears due to the interaction induced by their large dipole moments when they are in Rydberg states. This talk will describe our demonstration of the Rydberg blockade between two atoms individually trapped in optical tweezers at a distance of 4 micrometers. The rubidium 87 atoms are prepared in the state |↑〉 = |F =2, M=2〉, and subsequently excited to the Rydberg state 58d3/2, |r〉, by a two-photon transition. A consequence of the blockade mechanism is that the atoms are excited in an entangled state of the form (|r,↑〉 + |↑,r〉) / √2. The signature of the production of this state is the enhanced Rabi frequency of the oscillation of the probability to excite only one of the two atoms, with respect to the Rabi frequency of the excitation of one atom when it is alone. We have then mapped the Rydberg state |r〉 onto a second ground state |↓〉 = |F =1, M=1〉 to generate the Bell state (|↓,↑〉 + |↑,↓〉) / √2. We analyse the amount of entanglement by global Raman rotations on the two atoms. We have measured a fidelity of the two-atom state produced of 0.74. Finally the talk will report our progress on the building of a new setup aiming at entangling a larger number of atoms. |
| 2:45pm-3:15pm | L. Paul Parazzoli, Sandia National Laboratories | Adiabatic Quantum Computing with Neutral Atoms | Abstract. We are developing, both theoretically and experimentally, a neutral atom qubit approach to adiabatic quantum computing (AQC). It has been shown in that neutral atoms trapped in optical far off-resonance traps (FORTs) can be used for two-qubit gates using interactions mediated by electric-dipole coupling of a coherently excited Rydberg state. A similar neutral atom system is attractive for this work due to the long-term coherence of the qubit ground states, the potential of multi-dimensional arrays of qubits in FORT traps and the potential for strong, tunable interactions via Rydberg-dressed atoms. If these arrays can be designed to encode a desirable computation into the system Hamiltonian one could use these tunable interactions along with single-qubit rotations to perform an AQC. Taking full advantage of Sandia’s microfabricated diffractive optical elements (DOEs), we plan to implement such an array of traps and use Rydberg-dressed atoms to provide a controlled atom-atom interaction in atomic cesium. We forecast that these DOEs can provide the functions of trapping, single-qubit control and state readout resulting in an important engineering stride for quantum computation with neutral atoms. We will develop this experimental capability to generate a two-qubit adiabatic evolution aimed specifically toward demonstrating the twoqubit quadratic unconstrained binary optimization (QUBO) routine. We are studying the two-qubit QUBO problem to test the immunity of AQC to noise processes in the control interactions as well as dissipation mechanisms associated with the trapping. We are developing our theoretical and experimental capabilities through key collaborations with The University of Wisconsin, NIST and The University of New Mexico. |
| 3:15pm-3:45pm | Jae Hoon Lee, University of Arizona | Sub-wavelength Resonance Imaging and Robust Addressing of Atoms in an Optical Lattice | Abstract. We demonstrate a resonance imaging protocol for optical lattices that enables robust preparation and single qubit addressing of atoms with sub-wavelength resolution. Our setup consists of a 3D optical lattice, and a superimposed long-period (66 lattice sites) 1D “superlattice” that creates a position dependent shift of the transition frequency between two spin states in the ground manifold. We show that isolated planes of atoms can be prepared by flipping resonant spins with a microwave pulse and removing the remaining non-resonant spins. A second microwave pulses in a translated superlattice subsequently allow us to image these planes with a resolution better than 200 nm. We further show that composite pulse techniques can reduce the sensitivity of the addressing to small variations in the relative position and intensity of the lattices. This robustness is achieved by applying numerically optimized, phase modulated pulses that have a constant atomic response within the region of error. For example, we apply a composite microwave pulse that flips the spin with near unit fidelity for all atoms that are positioned within a target spatial region (e.g., one lattice site), while conserving the spin of the atoms outside of that region (e.g., neighboring lattice sites). Furthermore, with this technique, we show that we are able to implement independent unitaries (single qubit quantum gates) across several adjacent lattice sites with a single composite pulse. Finally, we perform randomized benchmarking, similar to that done by Olmschenk et al., to measure the error per randomized computational gate using composite pulses. |