Bulletin of the American Physical Society
39th Annual Meeting of the APS Division of Atomic, Molecular, and Optical Physics
Volume 53, Number 7
Tuesday–Saturday, May 27–31, 2008; State College, Pennsylvania
Session B2: Graduate Student Thesis Session |
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Chair: Robin Cote, University of Connecticut Room: Kern Building 112 |
Wednesday, May 28, 2008 11:00AM - 11:36AM |
B2.00001: Coherent manipulation of single electronic and nuclear spins in diamond Invited Speaker: The complex environment of solid-state systems poses a central challenge for solid-state realizations of quantum bits. Nevertheless, we show that the solid-state environment of a single spin can be understood, controlled, and even utilized as a resource. Using coherent manipulation of a single electronic spin associated with a nitrogen-vacancy (NV) center in diamond, we probe the $^{13}$C nuclear spin bath formed by impurities in the surrounding diamond lattice. We show that this environment is effectively separated into a set of individual, proximal $^{13}$C nuclear spins which are coupled coherently to the electron spin, and the remainder of the $^{13}$C nuclear spins, which cause the loss of coherence. By manipulating the NV center via microwave and optical excitation, we demonstrate robust, room-temperature initialization of the two-qubit register formed by the electronic spin and the nearest-neighbor $^{13}$C nuclear spin. Within this register, arbitrary quantum states can be transferred between the electronic and nuclear spin, while the nuclear spin qubit can be well isolated from the electron spin, even during optical polarization and measurement of the electronic state. Finally, we observe coherent interactions between individual nuclear spins, and demonstrate that they have excellent coherence properties, approaching those of isolated atoms and ions. Combined with teleportation-based quantum gates, such registers offer a basis for scalable, optically coupled quantum information systems. [Preview Abstract] |
Wednesday, May 28, 2008 11:36AM - 12:12PM |
B2.00002: Towards Hybrid Quantum Information Processing with Polar Molecules Invited Speaker: With the ongoing miniaturization of on-chip traps for atoms and ions it is timely to think about coherent interfaces between AMO and solid state systems with potential applications for new hybrid implementations for quantum computers. In this talk I will discuss a potential scenario, where ensembles of polar molecules serve as long-lived quantum memories for superconducting qubits and quantum information is transmitted via a high-Q microwave cavity. Polar molecules combine the exceptional features of a large electric dipole moment and long-lived rotational states with level splittings in the GHz regime. When trapped close to the surface of a chip this combination allows strong interactions with coherent solid state devices, e.g., superconducting microwave cavities or Josephson qubits. I will first introduce the system consisting of a single polar molecule coupled to a stripline cavity which realizes a cavity QED system in the microwave regime and discuss applications for quantum information processing, state detection and new cavity-assisted cooling schemes for polar molecules. I will then switch to molecular ensemble qubits where quantum information is encoded in collective spin or rotational excitations of an ensemble of $N$ molecules. Ensemble qubits benefit from a collectively enhanced coupling $\sim \sqrt{N}$ which allows quantum state transfer between the molecules and, e.g., a charge qubit on a timescale that is compatible with typical coherence times in a solid state environment. With the goal to protect ensemble qubits from collisions, I will finally discuss a scenario, where molecules are prepared in a crystalline phase under 1D trapping conditions and dipole moments aligned by an external field. [Preview Abstract] |
Wednesday, May 28, 2008 12:12PM - 12:48PM |
B2.00003: Solid State Analogs in Bose-Condensed Gases Invited Speaker: Bose-Einstein condensates in optical lattices have proven to be a powerful tool for emulating a wide variety of physical systems. Although our Rubidium condensates are a million times less dense than air, in several regards they also act like solids. In this talk, I demonstrate this behavior in three different experiments. First, similar to a piece of glass, the refractive index of the condensate changes the momentum of a photon propagating through it. This systematic shift of the photon recoil momentum due to the index of refraction was measured with a two-pulse light grating interferometer, and has important ramifications for precision measurements of the fine structure constant, $\alpha$. Second, a 1D light crystal is shown to create a lattice band structure that allows two atoms traveling at the same velocity to collide and scatter into two different velocity states (which is impossible in free space), allowing us to demonstrate parametric generation and amplification of ultracold atom pairs. Finally, the Superfluid-Mott Insulator transition was studied in a 3D lattice using microwave spectroscopy. Using a density dependent shift to the clock transition, we were able to spectroscopically distinguish sites with different occupation numbers, and to directly image sites with occupation number from 1 to 5, revealing the shell structure of the Mott Insulator phase. This work was performed at MIT, under the direction of David E. Pritchard and Wolfgang Ketterle [Preview Abstract] |
Wednesday, May 28, 2008 12:48PM - 1:24PM |
B2.00004: Remote Entanglement and Quantum Networks with Trapped Atomic Ions Invited Speaker: The recent developments of quantum information science and its potential applications have brought many of the fundamental questions of quantum physics to the mainstream of not only theoretical but also experimental physics. I discuss a system at the heart of these questions -- quantum entanglement of the spin states of two individual massive particles at a distance, as originally envisioned in Bohm's version of the Einstein-Podolsky-Rosen paradox. I present the theory and the experimental realization of the entanglement of two trapped atomic ions separated by 1 meter. Trapped ions are among the most attractive systems for scalable quantum information because they can be well isolated from the environment and manipulated easily with lasers. In particular, I discuss our results including the first explicit demonstration of both quantum entanglement between a single trapped ion and its single emitted photon, as well as entanglement between two macroscopically separated trapped ion quantum memories. The entanglement protocols used in these experiments, together with the recent developments of local entanglement between nearby ions based on their Coulomb interaction, can be used to create a platform for a scalable quantum information network or a distributed quantum computer, and perhaps confront some of the strangest features of quantum mechanics. [Preview Abstract] |
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