Southwest Quantum Information and Technology
Thirteenth Annual Meeting, February 17-20, 2011
Boulder, Colorado
Full Program | Thursday | Friday | Saturday | Sunday | All Sessions
| SESSION 3: Neutral Atom QIP | Session Chair: |
| 8:30am-9:15am | Markus Greiner, Harvard University | Quantum simulation of an antiferromagnetic Ising chain with longitudinal and transverse magnetic fields | Abstract. With single lattice site detection and control, the quantum gas microscope opens new possibilities for quantum simulations. It allows us to study quantum magnetism with ultracold atoms in optical lattices. We experimentally realize an antiferromagnetic Ising chain with longitudinal and transverse magnetic fields, and observe a quantum phase transition from a paramagnetic to an antiferromagnetic state. |
| 9:15am-9:45am | Mark Saffman, University of Wisconsin Madison | Towards multi-qubit computing with Rydberg blockade | Abstract. I will summarize recent progress in Rydberg blockade mediated quantum gates and then discuss approaches to developing multi-qubit neutral atom processors. Emphasis wil be placed on multi-qubit gate protocols, and the use of ensemble qubits for single atom loading, and efficient atom-light quantum interfaces. |
| 9:45am-10:15am | Carlos Riofrio, University of New Mexico | Quantum tomography of the full hyperfine manifold of atomic spins via continuous measurement on an ensemble | Abstract. Quantum state reconstruction techniques based on weak continuous measurement have the advantage of being fast, accurate, and almost non-perturbative. Moreover, they have been successfully implemented in experiments on large spin systems (PRL 97, 180403 (2006)). In this talk, we present a detailed review of the quantum tomographic algorithm developed by Silberfarb et al. (PRL 95, 030402 (2005)), and study its application to controlling large spin ensembles. In particular, we show reconstruction of states stored in the 16 dimensional ground-electronic hyperfine manifolds (F=3, F=4) of an ensemble of 133Cs atoms controlled by microwaves and radio-frequency magnetic fields and discuss our efforts in the undergoing experimental implementation. |
| 10:45am-11:15am | Jae Hoon Lee, University of Arizona | Quantum Control of the Motional and Internal Degrees of Freedom of Neutral Atoms | Abstract. Cold trapped atoms provide an excellent platform on which to explore fundamental aspects of quantum information science, due in part to long coherence times and in part to the diverse sets of tools available for quantum manipulation. In this talk we discuss recent experimental progress towards robust quantum control of motional and ground hyperfine states of 133Cs atoms. An essential aspect of quantum information processing in optical lattices is the ability to prepare and address atoms with single-site resolution. In principle this can be done via "resonance imaging", using e. g. a combination of spatially varying light shifts and microwave pulses to change the internal state of atoms at well defined positions. In our current, first generation experiment we superimpose a long-period 1D standing wave on top of our 3D optical lattice, flip the spins of atoms in planes where the light shifted transition frequency matches that of the microwave field, and remove the remaining atoms from the lattice. Using composite pulse techniques we can make this preparation step robust against small variations in the relative position of the lattices. In a separate experiment we explore the use of DC, rf and microwave fields to manipulate the internal quantum state associated with the 16-dimensional ground hyperfine manifold of the Cs atom. Using robust control techniques, we demonstrate quantum state mapping from arbitrary initial to final states with fidelities of 98% or better, in the presence of errors and inhomogeneities in the control fields. We also study successive applications of state mapping waveforms, with the goal of separating qudit initialization and readout errors from state mapping errors, and to reliably measure state mapping fidelities in excess of 99%. |
| 11:15am-11:45am | Steven Olmschenk, Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland Department of Physics | Randomized benchmarking of atomic qubits and differential light shift cancellation in an optical lattice | Abstract. We perform randomized benchmarking on atomic qubits confined in an optical lattice. Single qubit rotations are implemented using microwaves, with a measured average error per gate of 1.4(1) x 10^-4 that is dominated by the decoherence time of the system. A method to extend the coherence time by cancellation of up to 95(2)% of the differential light shift in the ground state of rubidium is also demonstrated. Finally, we discuss how these gate operations might be performed with single-lattice-site addressability for more advanced applications in quantum information. |
| 11:45am-12:15pm | Andrea Alberti, Universität Bonn | Engineering Coherences at Single-Atom Level | Abstract. We report on our capabilities to coherently control individual neutral Cs atoms in a 1D optical lattice with single site resolution [1,2]. By controlling the atoms through spin-dependent optical potentials we are able to entangle their internal and external degrees of freedom, allowing us to demonstrate 1D quantum walks in real space. Multi-path matter wave interference results in characteristic patterns of coherently delocalized atoms over many lattice sites [3]. In addition, microwave control of atomic motion is used to prepare atoms in predefined motional quantum states, e.g. in the vibrational ground state [4]. Presently we are exploring single-atom interferometry using spatially delocalized atoms in a Mach-Zehnder-like geometry. The atomic wave packets accumulate a relative phase at their respective positions from potential differences, making it a microscopic quantum detector of forces, such as magnetic field gradients or accelerations. Spatial separations over more than 20 sites still yields usable coherent phase evolution. These results lay the basis for interferometric detection of collisional phases and two-atom entanglement generation. [1] M. Karski et al., Imprinting Patterns of Neutral Atoms in an Optical Lattice using Magnetic Resonance Techniques, New J. Phys. 12, 065027 (2010) [2] M. Karski et al., Nearest-Neighbor Detection of Atoms in a 1D Optical Lattice by Fluorescence Imaging, Phys. Rev. Lett. 102, 053001 (2009) [3] M. Karski et al., Quantum Walk in Position Space with Single Optically Trapped Atoms, Science 325, 174 (2009) [4] L. Förster et al., Microwave Control of Atomic Motion in Optical Lattices, Phys. Rev. Lett. 103, 233001 (2009) |