Southwest Quantum Information and Technology

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

Full Program | Thursday | Friday | Saturday | Sunday

SESSION 12: Quantum Simulation
Session Chair:
10:15-10:45	Mohan Sarovar, University of California, Berkeley
	Quantum mechanical aspects of photosynthesis
	Abstract. Identification of non-trivial quantum mechanical effects in the functioning of biological systems has been a long-standing and elusive goal in the fields of physics, chemistry and biology. Recent progress in control and measurement technologies, especially in the optical spectroscopy domain, have made possible the identification of such effects. In particular, electronic coherence was recently shown to survive for relatively long times in photosynthetic light harvesting complexes despite the effects of noisy bio-molecular environments. Combining techniques from quantum information, quantum dynamical theory and chemical physics, we performed several detailed studies to characterize the extent and nature of quantum dynamics in light harvesting structures. I will present results that demonstrate (i) the presence of long-lived quantum entanglement in these biologically relevant structures, (ii) the lack of sustained quantum speedup in light harvesting complex dynamics, and (iii) the effect of environmental fluctuations on coherence and transport properties in these systems. Our results scrutinize the fine details of light harvesting complex dynamics and reveal the complex interplay between coherent and decoherent dynamics present in these systems.
10:45-11:15	Norbert Schuch, California Institute of Technology
	An efficient algorithm to find mean field and Matrix Product State solutions for one-dimensional systems
	Abstract. We prove that the best approximation to ground states of one-dimensional quantum systems within the two most common variational ansatzes, namely the mean field ansatz and Matrix Product States, can be found efficiently. This shows that the corresponding variational methods, in particular the Density Matrix Renormalization Group method, can be realized in a provably efficient way, placing their success on a rigorous footing. Moreover, our findings imply that ground states of commuting Hamiltonians in one dimension can be found efficiently.
11:15-11:45	Michael Biercuk, National Institute of Standards and Technology
	Spin Squeezing, Large-Scale Entanglement, and Quantum Simulation in Ion Crystals
	Abstract. M.J. Biercuk, H. Uys, D. Meiser, A. P. VanDevender, C. Ospelkaus, N. Shiga, W. M. Itano, and J. J. Bollinger We describe experimental and theoretical efforts aimed at the realization of nonlinear multipartite interactions using planar ion crystals in a Penning trap. This system benefits from the ability to confine large ion arrays with regular and stable crystalline order, and direct measures of particle number through resonant fluorescence detection. A global entangling interaction is engineered using state-dependent optical dipole forces, resulting in a simple distance-independent Ising interaction similar to single-axis-twisting spin squeezing. We present direct observations of optical-dipole-force excitation of the center-of-mass (COM) mode for a planar crystal using phase-coherent Doppler velocimetry. By combining state-dependent excitation of the COM mode with microwave-mediated global spin control in arrays of up to ~150 ions, we demonstrate a frequency-dependent loss of phase coherence in the spin ensemble due to coherent interaction of spin and motion. Prospects for realizing true deterministic spin squeezing using trapped ions, including the influence of dissipation via elastic Rayleigh scattering are presented, and future experimental directions described.