Southwest Quantum Information and Technology

Twelfth Annual Meeting, February 18-21, 2010
Santa Fe, New Mexico

Full Program | Thursday | Friday | Saturday | Sunday

SESSION 2: Trapped Ion QI
Session Chair:
8:30-9:15	Rainer Blatt, University of Innsbruck
	Quantum Information Science with Trapped Ca+ Ions
	Abstract. Trapped strings of cold ions provide an ideal system for quantum information processing. The quantum information can be stored in individual ions and these qubits can be individually prepared; the corresponding quantum states can be manipulated and measured with nearly 100% detection efficiency. With a small ion-trap quantum computer based on up to eight trapped Ca+ ions as qubits we have generated genuine quantum states in a pre-programmed way. In particular, we have generated GHZ and W states in a fast and scalable way and we have demonstrated for the first time a Toffoli gate with trapped ions which is analyzed via state and process tomography. High fidelity CNOT-gate operations are investigated towards fault-tolerant quantum computing and using logical qubits encoded in decoherence-free subspaces, a universal set of gate operations was implemented and analyzed. As applications of quantum information processing, an experimental state-independent test of quantum contextuality was performed, a simulation of the Dirac equation was implemented and a quantum walk with a trapped ion was realized.
9:15-9:45	David Hanneke, National Institute of Standards and Technology
	Putting the pieces together: Recent progress with trapped ions at NIST
	Abstract. Storing quantum bits in the internal states of trapped atomic ions has proven a successful approach to quantum information processing because of long coherence times and precise interaction with light fields for coherent control and entanglement generation. Here, we present an experiment that combines a complete set of scalable techniques to realize a programmable two-qubit quantum processor. We also highlight other work at NIST that aims at facilitating the realization of large-scale quantum processors using trapped ions. This work includes the development of scalable trap technologies, studies of dynamical-decoupling techniques for memory preservation, and progress towards large scale entanglement generation and quantum simulation. *Work supported by DARPA, NSA, ONR, IARPA, Sandia, and the NIST Quantum Information Program.
10:15-10:45	David Hayes, Joint Quantum Institute/University of Maryland
	Entanglement of Atomic Qubits using an Optical Frequency Comb
	Abstract. Our group has demonstrated the use of an optical frequency comb to coherently control and entangle atomic qubits. A train of off-resonant ultrafast laser pulses is used to efficiently and coherently transfer population between electronic and vibrational states of trapped atomic ions and implement entangling quantum logic gates with high fidelity. This technique can be extended to the strong field limit with single ultrafast pulses, and this general approach can be applied to the quantum control of more complex systems, such as large collections of interacting atoms or molecules.
10:45-11:15	Nikolaos Daniilidis, Unifersity of California, Berkeley
	Towards wiring up trapped ions
	Abstract. We are pursuing experiments aiming at a transmission-line interface to transfer quantum information between distant ions: An oscillating trapped ion induces oscillating image charges in the trap electrodes. If this current is sent to the electrodes of a second trap, it influences the motion of an ion in the second trap. The expected time for a complete exchange of the motional states can be 1 ms for coupling via a floating conductor located above a surface trap. Alternatively resonant-circuit based geometries with increased coupling rates are also considered. We discuss coupling rates and expected heating rates for different approaches. In addition we discuss trap operation in the presence of a floating conductor. The latter will serve as the coupling electrode in experiments aiming at exchange of the motional states of ions in neighboring trapping regions. This “wire-mediated” coupling may be used for scalable quantum information processing, but may also interconnect atomic systems to solid-state systems.
11:15-11:45	Gang Shu, University of Washington
	Novel Ion Trap for Efficient Fluorescence Collection from Trapped Ion Qubits
	Abstract. Efficient ion fluorescence collection is critical for fast reliable qubit state detection and higher photon collection rates from single trapped ions or atoms would lead to more efficient single-photon sources and ion-photon entanglement. By integrating a high N.A. spherical mirror into a linear Paul trap, we achieved 10% photon collection efficiency from a single Barium ion qubit. Based on the current successful trap, we designed and built a novel trap in which the reflective optical surface serves as the RF electrode. The new trap geometry is very open and almost 30% of the photons emitted by the ion will be intercepted. Additionally, the axial symmetry of the trap provides means for self-alignment of the ion trapping position and the optical axis of the spherical mirror. Its smaller size will proportionally reduce the spherical aberration so that we can achieve diffraction-limited ion image, and attempt to couple ion fluorescence into a single mode optical fiber for remote ion entanglement. The design can be easily miniaturized and fabricated with standard MEMS technology. Compared to refractive optics systems, our solution has the advantage of simplicity, low cost, flexibility and scale-up potential.