Browsing by Subject "Optical traps"
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Item Atomic Fock states and quantum computing(2009-08) Wan, Shoupu; Niu, Qian; Raizen, Mark G.The potential impact of quantum computing has stimulated a worldwide effort to develop the necessary experimental and theoretical resources. In the race for the quantum computer, several candidate systems have emerged, but the ultimate system is still unclear. We study theoretically how to realize atomic Fock states both for fermionic and bosonic atoms, mainly in one-dimensional optical traps. We demonstrate a new approach of quantum computing based on ultracold fermionic atomic Fock states in optical traps. With the Pauli exclusion principle, producing fermionic atomic Fock states in optical traps is straightforward. We find that laser culling of fermionic atoms in optical traps can produce a scalable number of ultra-high fidelity qubits. We show how each qubit can be independently prepared, and how to perform the required entanglement operations and detect the qubit states with spatially resolved, single-atom detection with adiabatic trap-splitting and fluorescence imaging. On the other hand, bosonic atoms have a strong tendency to stay together. One must rely on strong repulsive interactions to produce bosonic atomic Fock states. To simulate the physical conditions of producing Fock states with ultracold bosonic atoms, we study a many-boson system with arbitrary interaction strength using the Bethe ansatz method. This approach provides a general framework, enabling the study of Fock state production over a wide range of realistic experimental parameters.Item Biological nanofibers in a standing wave optical trap(2007-12) Ebner, Maximilian; Florin, Ernst-LudwigTo explain fundamental processes in molecular and cell biology a detailed description of the interaction of the relevant components involved is required. Hence, single molecule experiments have to be carried out in order to omit averaging of the interaction. For observation of small particles in a non-intrusive fashion optical traps can be used for immobilization and manipulation. The proposed design of a Gaussian standing wave optical trap, feasible to trap unprecedently small particles due to steep intensity gradients and the depletion of the scattering force is presented. In its realization with a reflective slide, it is used to demonstrate the capability of this tool to trap small biological particles. Nanofibers model a reduction in dimensionality, thus leading the way to single molecules. The high ratio of axial-to-lateral trap stiffness in the standing wave optical trap causes the nanofibers to lay in the focal plane. Microtubules with a diameter of 25nm were trapped and moved in the focal plane. Long time observation of microtubule bundles using darkfield microscopy is achieved and used to characterize the trapping efficiency. Bundles of three microtubules were held in focus over a time period of hours using a trapping power of only 6mW. The suitable conditioning of the sample chamber with a heating system is demonstrated by polymerizing microtubules inside the sample chamber, pointing the way to a controlled assembly of microtubule bundles.