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Bright solitary waves and nonequilibrium dynamics in atomic BoseEinstein condensates
, 2012
"... In this thesis we investigate the static properties and nonequilibrium dynamics of bright solitary waves in atomic BoseEinstein condensates in the zerotemperature limit, and we investigate the nonequilibrium dynamics of a driven atomic BoseEinstein condensate at finite temperature. Bright solit ..."
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In this thesis we investigate the static properties and nonequilibrium dynamics of bright solitary waves in atomic BoseEinstein condensates in the zerotemperature limit, and we investigate the nonequilibrium dynamics of a driven atomic BoseEinstein condensate at finite temperature. Bright solitary waves in atomic BoseEinstein condensates are nondispersive and solitonlike matterwaves which could be used in future atominterferometry experiments. Using the meanfield, GrossPitaevskii description, we propose an experimental scheme to generate pairs of bright solitary waves with controlled velocity and relative phase; this scheme could form an important part of a future atom interferometer, and we demonstrate that it can also be used to test the validity of the meanfield model of bright solitary waves. We also develop a method to quantitatively assess how solitonlike static, threedimensional bright solitary waves are; this assessment is particularly relevant for the design of future experiments. In reality, the nonzero temperatures and highly nonequilibrium dynamics occurring in a bright solitary wave interferometer are likely to necessitate a theoretical description which explicitly accounts for the noncondensate fraction. We show that a secondorder, numberconserving description offers a minimal selfconsistent treatment of the relevant condensate – noncondensate interactions at low temperatures and for moderate noncondensate fractions. We develop a method to obtain a fullydynamical numerical solution to the integrodifferential equations of motion of this description, and solve these equations for a driven, quasionedimensional test system. We show that rapid noncondensate growth predicted by lowerorder descriptions, and associated with linear dynamical instabilities, can be damped by the selfconsistent treatment of interactions included in the secondorder description. 1 Bright solitary waves and nonequilibrium dynamics in atomic BoseEinstein condensates
c ○ Rinton Press HIGHFIDELITY QUANTUM CONTROL USING ION CRYSTALS IN A PENNING TRAP
, 2009
"... We provide an introduction to the use of ion crystals in a Penning trap [1, 2, 3, 4] for experiments in quantum information. Macroscopic Penning traps allow for the containment of a few to a few million atomic ions whose internal states may be used in quantum information experiments. Ions are laser ..."
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We provide an introduction to the use of ion crystals in a Penning trap [1, 2, 3, 4] for experiments in quantum information. Macroscopic Penning traps allow for the containment of a few to a few million atomic ions whose internal states may be used in quantum information experiments. Ions are laser Doppler cooled [1], and the mutual Coulomb repulsion of the ions leads to the formation of crystalline arrays [5, 6, 7, 8]. The structure and dimensionality of the resulting ion crystals may be tuned using a combination of control laser beams and external potentials [9, 10]. We discuss the use of twodimensional 9Be + ion crystals for experimental tests of quantum control techniques. Our primary qubit is the 124 GHz groundstate electron spin flip transition, which we drive using microwaves [11, 12]. An ion crystal represents a spatial ensemble of qubits, but the effects of inhomogeneities across a typical crystal are small, and as such we treat the ensemble as a single effective spin. We are able to initialize the qubits in a simple state and perform a projective measurement [1] on the system. We demonstrate full control of the qubit Bloch vector, performing arbitrary highfidelity rotations (τπ ∼200 µs). Randomized Benchmarking [13] demonstrates an error per gate (a Paulirandomized π/2 and π pulse pair) of 8±1×10−4. Ramsey interferometry and spinlocking [14] measurements are used to elucidate the limits of qubit coherence in the system, yielding a typical freeinduction decay coherence time of T2 ∼2 ms, and a limiting T1ρ ∼688 ms. These experimental specifications make ion crystals in a Penning trap ideal candidates for novel experiments in quantum control. As such, we briefly describe recent efforts aimed at studying the errorsuppressing capabilities of dynamical
Acknowledgements
, 2010
"... Copyright statement This thesis is the result of the author’s original research. It has been composed by the author and has not been previously submitted for examination which has led to the award of a degree. The copyright of this thesis belongs to the author under the terms of the United Kingdom ..."
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Copyright statement This thesis is the result of the author’s original research. It has been composed by the author and has not been previously submitted for examination which has led to the award of a degree. The copyright of this thesis belongs to the author under the terms of the United Kingdom Copyright Acts as qualified by University of Strathclyde Regulation 3.50. Due acknowledgement must always be made of the use of any material contained in, or derived from, this thesis. Signed: Date:
A Digital Frequency Source for Movement of Ultracold Atoms by AcoustoOptic Deflection
, 2014
"... This thesis documents the development of a frequency source based on a field programmable gate array (FPGA) and a direct digital synthesiser (DDS). The source was used to drive the two inputs of a dualaxis acoustooptic deflector (AOD), an integral component in a steerable optical tweezer unit des ..."
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This thesis documents the development of a frequency source based on a field programmable gate array (FPGA) and a direct digital synthesiser (DDS). The source was used to drive the two inputs of a dualaxis acoustooptic deflector (AOD), an integral component in a steerable optical tweezer unit designed for use with ultracold 87Rb and 40K. By synchronously changing the frequencies of the paired inputs to the AOD, an optical beam was able to be moved in two dimensions. The frequency source was used to trap and smoothly move samples of ultracold 87Rb over several millimetres, and by quickly toggling the inputs between multiple pairs of frequencies, multiple clouds were confined and moved in timeaveraged potentials. The utility of the FPGA/DDS unit is shown, most notably by simultaneously evaporating four independent clouds through the BoseEinstein Condensate (BEC) phase transition. ii Acknowledgements I’ve been very fortunate to have had such profound role models during my time in the