Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session B6: Controlling Dissipation in Quantum Systems |
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Sponsoring Units: DAMOP GQI Chair: Jacob Taylor, National Institute of Standards and Technology Room: Portland Ballroom 253 |
Monday, March 15, 2010 11:15AM - 11:51AM |
B6.00001: Quantum phases through dissipation Invited Speaker: |
Monday, March 15, 2010 11:51AM - 12:27PM |
B6.00002: Dissipation with Rydberg atoms Invited Speaker: Following Feynman and as elaborated on by Lloyd, a universal quantum simulator (QS) is a controlled quantum device which efficiently reproduces the dynamics of any other many particle quantum system with short range interactions. This dynamics can refer to both coherent Hamiltonian and dissipative open system evolution. Here we show that laser excited Rydberg atoms in large spacing optical or magnetic lattices provide an efficient implementation of a universal QS for spin models involving (high order) n-body interactions. This includes the simulation of Hamiltonians of exotic spin models involving n-particle constraints such as the Kitaev toric code, color code, and lattice gauge theories with spin liquid phases. In addition, it provides the ingredients for dissipative preparation of entangled states based on engineering n-particle reservoir couplings. The key basic building blocks of our architecture are efficient and high-fidelity n-qubit entangling gates via auxiliary Rydberg atoms, including a possible dissipative time step via optical pumping. This allows to mimic the time evolution of the system by a sequence of fast, parallel and high-fidelity n-particle coherent and dissipative Rydberg gates. [Preview Abstract] |
Monday, March 15, 2010 12:27PM - 1:03PM |
B6.00003: Strong Dissipation Inhibits Losses and Induces Correlations in Cold Molecular Gases Invited Speaker: Atomic quantum gases in the strong-correlation regime offer unique possibilities to explore a variety of many-body quantum phenomena. Reaching this regime has usually required both strong elastic and weak inelastic interactions, as the latter produce losses. We show that strong inelastic collisions can actually inhibit particle losses and drive a system into a strongly-correlated regime. Studying the dynamics of ultracold molecules in an optical lattice confined to one dimension, we show that the particle loss rate is reduced by a factor of 10. Adding a lattice along the one dimension increases the reduction to a factor of 2000. Our results open up the possibility to observe exotic quantum many-body phenomena with systems that suffer from strong inelastic collisions. [Preview Abstract] |
Monday, March 15, 2010 1:03PM - 1:39PM |
B6.00004: Control in cavity QED with many atoms Invited Speaker: Cavity QED in the optical regime has two avenues for dissipation: spontaneous emission of the atoms and escape of the light from the cavity. Control of the dynamics in the cavity QED relies on both channels and in some cases permits the preservation of a quantum state a long time after the expected decay of the system. This talk presents experiments with Rb atoms in a cavity QED system where the single atom coupling and the decay rates are comparable. Single mode and two mode monitoring offer feedback possibilities to preserve atom-cavity oscillatory exchange and ground state superpositions. Work supported by NSF and performed in collaboration with D. G. Norris, H. J. Carmichael, and P. Barberis-Blostein. [Preview Abstract] |
Monday, March 15, 2010 1:39PM - 2:15PM |
B6.00005: Quantum state preparation by phase randomization Invited Speaker: A computation in adiabatic quantum computing is implemented by traversing a path of eigenstates of a continuous family of Hamiltonians. We introduce a method that traverses a discretized form of the path by applying, at each step, the instantaneous Hamiltonian for a random time. The resulting decoherence approximates a projective measurement onto the desired eigenstate, achieving a version of the quantum Zeno effect. The average absolute evolution time required by our method is proportional to the square of the length of the path of eigenstates, and inversely proportional to the minimum energy gap. The dependence of the cost on the gap is optimal. Our method can be viewed as a rigorous, and more general, adiabatic approximation. It is a conceptually clear example of how sometimes some decoherence helps. Applications to unstructured search and quantum sampling are considered. In particular, we discuss the quantum simulated annealing algorithm for solving combinatorial optimization problems. This algorithm provides a quadratic speed-up in the gap of the stochastic matrix over its classical counterpart implemented via Markov chain Monte Carlo. [Preview Abstract] |
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