Southwest Quantum Information and Technology

Eleventh Annual Meeting, February 19-22, 2009
Seattle, Washington

Full Program | Thursday | Friday | Saturday | Sunday

SESSION 2: Neutral Atom QI
Session Chair:
8:30-9:15	David Weiss, Penn State (invited)
	Quantum computing with atoms in a 3D optical lattice
	Abstract. We have demonstrated trapping and imaging of 250 single atoms in a 3D optical lattice. The 5 micron lattice spacing is large enough that individual atoms can be addressed using lasers and microwaves in a way that does not affect the quantum coherence of other atoms. Our goal is to use these trapped atoms as qubits. So far, we fill a random half of the lattice sites, but a combination of site-selective state changes and state-selective lattice translations should allow us to verifiably fill all vacancies. We will describe our experiments to date and our plans for entangling atoms and implementing a neutral atom quantum computer.
9:15-9:45	Poul Jessen, University of Arizona
	Quantum Control of Large Atomic Hyperfine Manifolds
	Abstract. Laboratory techniques to manipulate and observe ultracold atoms make these an attractive platform for testing new ideas in quantum control and measurement. I will review a series of experiments in which we have used tensor AC Stark shifts and magnetic fields to drive non-trivial quantum dynamics of a large spin-angular momentum associated with an atomic hyperfine ground state. The nonlinear spin Hamiltonian is sufficiently general to achieve universal quantum control over the 2F+1 dimensional state space, and allows us to generate arbitrary spin states and perform a full quantum state reconstruction of the result. We have implemented and verified time optimal controls to generate a broad variety of spin states, as well as an adiabatic scheme to generate spin-squeezed states for metrology. Most recently we have used our control and measurement tools to realize a common paradigm for quantum chaos known as the quantum kicked top. Direct observation of the phase space dynamics of this system has given an unprecedented look at quantum/classical correspondence. We are now implementing a new scheme for quantum control of an entire ground hyperfine manifold, based solely on interaction with DC, radiofrequency and microwave magnetic fields. The longer coherence times available with this approach will allow us to explore new ideas related to robust control and constructive design of unitary transformations.
10:15-10:45	Benjamin Lev, University of Illinois at Urbana-Champaign
	Exploring exotic matter through the quantum manipulation of dipolar atoms
	Abstract. Highly magnetic atoms such as dysprosium offer the ability to create strongly correlated matter in both atomic physics and quantum optics settings. In addition, these atoms will form the key ingredient in novel devices possessing unsurpassed sensitivity and resolution for the microscopy of condensed matter materials. Our group aims to develop technology to perform laser cooling---and subsequent trapping in atom chips and optical lattices---of dysprosium. This will lead to three research projects: the investigation of quantum liquid crystal physics in 2D fermoinic dipolar lattices; the exploration of non-equilibrium quantum phase transitions in many body cavity QED; and the development of atom chip microscopy at the 10^-10 magnetic flux quantum level.
10:45-11:15	Nathan Lundblad, Joint Quantum Institute/NIST/Univ. of Maryland
	Optical lattice-based addressing and control of long-lived neutral-atom qubits
	Abstract. Quantum computational platforms are driven by competing needs: the isolation of the quantum system from the environment to prevent decoherence, and the ability to control the system with external fields. For example, neutral-atom optical-lattice architectures provide environmental isolation through the use of "clock" states that are robust against changing external fields, yet those same external fields are inherently useful for qubit addressing. Here we demonstrate a technique to address a spatially dense field-insensitive qubit register. A subwavelength-scale effective magnetic-field gradient permits the addressing of particular "marked" elements of the lattice register, leaving unmarked qubits unaffected, with little worry about crosstalk or leakage. We demonstrate this technique with rubidium atoms, and show that we can robustly perform single-qubit rotations on qubits located at addressed lattice sites. This precise coherent control is an important step forward for lattice-based neutral-atom quantum computation, and is applicable to state transfer and qubit isolation in other architectures using field-insensitive qubits.
11:15-11:45	Iris Reichenbach, University of New Mexico
	Two-qubit quantum logic gates via optical Feshbach resonances in alkaline-earth-like atoms
	Abstract. The ability to implement quantum information processing in neutral atoms hinges critically on the ability to coherently control both the internal states and the interactions between two such atoms. We show that alkaline-earth-like atoms are uniquely suited to the task of quantum computing, due to their rich but controllable internal structure, including the nuclear spin, and their very narrow 1S0 -> 3P1 intercombination transition, which makes the application of optical Feshbach resonances possible. Optical Feshbach resonances allow for fine tuning of the interaction strength over a wide range, even making it possible to completely turn off the interaction, thus improving the coherence time. Theoretical modeling of the optical Feshbach resonance on the example of 171Yb shows their potential in the implementation of two qubit gates through nuclear spin exchange.