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You searched for +publisher:"University of New Mexico" +contributor:("Caves, Carlton M."). Showing records 1 – 3 of 3 total matches.

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University of New Mexico

1. Jiang, Zhang. Particle Correlations in Bose-Einstein Condensates.

Degree: Physics & Astronomy, 2014, University of New Mexico

The impact of interparticle correlations on the behavior of Bose-Einstein Condensates (BECs) is discussed using two approaches. In the first approach, the wavefunction of a BEC is encoded in the <var>N</var>-particle sector of an extended "catalytic state''. Going to a time-dependent interaction picture, we can organize the effective Hamiltonian by powers of <var>N</var><sup> -1/2</sup>. Requiring the terms of order <var>N</var>1/2 to vanish, we get the Gross-Pitaevskii Equation. Going to the next order, <var>N</var>0, we obtain the number-conserving Bogoliubov approximation. Our approach allows one to stay in the Schrödinger picture and to apply many techniques from quantum optics. Moreover, it is easier to track different orders in the Hamiltonian and to generalize to the multi-component case. In the second approach, I consider a state of <var>N</var>=<var>l</var>×<var>n</var> bosons that is derived by symmetrizing the <var>n</var>-fold tensor product of an arbitrary <var>l</var>-boson state. Particularly, we are interested in the pure state case for <var>l</var>=2, which we call the Pair-Correlated State (PCS). I show that PCS reproduces the number-conserving Bogoliubov approximation; moreover, it also works in the strong interaction regime where the Bogoliubov approximation fails. For the two-site Bose-Hubbard model, I find numerically that the error (measured by trace distance of the two-particle RDMs) of PCS is less than two percent over the entire parameter space, thus making PCS a bridge between the superfluid and Mott insulating phases. Amazingly, the error of PCS does not increase, in the time-dependent case, as the system evolves for longer times. I derive both time-dependent and -independent equations for the ground state and the time evolution of the PCS ansatz. The time complexity of simulating PCS does not depend on <var>N</var> and is linear in the number of orbitals in use. Compared to other methods, e.g, the Jastrow wavefunction, the Gutzwiller wavefunction, and the multi-configurational time-dependent Hartree method, our approach does not require quantum Monte Carlo nor demanding computational power. Advisors/Committee Members: Caves, Carlton M., Landahl, Andrew, Miyake, Akimasa, Prasad, Sudhakar.

Subjects/Keywords: particle correlation; Bose-Einstein condensate

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APA (6th Edition):

Jiang, Z. (2014). Particle Correlations in Bose-Einstein Condensates. (Doctoral Dissertation). University of New Mexico. Retrieved from http://hdl.handle.net/1928/24564

Chicago Manual of Style (16th Edition):

Jiang, Zhang. “Particle Correlations in Bose-Einstein Condensates.” 2014. Doctoral Dissertation, University of New Mexico. Accessed June 15, 2019. http://hdl.handle.net/1928/24564.

MLA Handbook (7th Edition):

Jiang, Zhang. “Particle Correlations in Bose-Einstein Condensates.” 2014. Web. 15 Jun 2019.

Vancouver:

Jiang Z. Particle Correlations in Bose-Einstein Condensates. [Internet] [Doctoral dissertation]. University of New Mexico; 2014. [cited 2019 Jun 15]. Available from: http://hdl.handle.net/1928/24564.

Council of Science Editors:

Jiang Z. Particle Correlations in Bose-Einstein Condensates. [Doctoral Dissertation]. University of New Mexico; 2014. Available from: http://hdl.handle.net/1928/24564


University of New Mexico

2. Lang, Matthias Dominik. Measures of Nonclassical Correlations and Quantum-Enhanced Interferometry.

Degree: Physics & Astronomy, 2015, University of New Mexico

In the first part of this dissertation a framework for categorizing entropic measures of nonclassical correlations in bipartite quantum states is presented. The measures are based on the difference between a quantum entropic quantity and the corresponding classical quantity obtained from measurements on the two systems. Three types of entropic quantities are used, and three different measurement strategies are applied to these quantities. Many of the resulting measures of nonclassical correlations have been proposed previously. Properties of the various measures are explored, and results of evaluating the measures for two-qubit quantum states are presented. To demonstrate how these measures differ from entanglement we move to the set of Bell-diagonal states for two qubits, which can be depicted as a tetrahedron in three dimensions. We consider the level surfaces of entanglement and of the correlation measures from our framework for Bell-diagonal states. This provides a complete picture of the structure of entanglement and discord for this simple case and, in particular, of their nonanalytic behavior under decoherence. The pictorial approach also indicates how to show that all of the proposed correlation measures are neither convex nor concave. In the second part we look at two practical interferometric setups that use nonclassical states of light to enhance their performance. First we consider an interferometer powered by laser light (a coherent state) into one input port and ask the following question: what is the best state to inject into the second input port, given a constraint on the mean number of photons this state can carry, in order to optimize the interferometer's phase sensitivity? This question is the practical question for high-sensitivity interferometry. We answer the question by considering the quantum Cram\'er-Rao bound for such a setup. The answer is squeezed vacuum. Then we analyze the ultimate bounds on the phase sensitivity of an interferometer, given the constraint that the state input to the interferometer's initial 50:50 beam splitter B is a product state of the two input modes. Requiring a product state is a natural restriction: if one were allowed to input an arbitrary, entangled two-mode state |Ξ > to the beam splitter, one could generally just as easily input the state B|Ξ > directly into the two modes after the beam splitter, thus rendering the beam splitter unnecessary. We find optimal states for a fixed photon number and for a fixed mean photon number. Our results indicate that entanglement is not a crucial resource for quantum-enhanced interferometry. Initially the analysis for both of these setups is performed for the idealized case of a lossless interferometer. Then the analysis is extended to the more realistic scenario where the interferometer suffers from photon losses. Advisors/Committee Members: Caves, Carlton M., Miyake, Akimasa, Dunlap, David, Somma, Rolando.

Subjects/Keywords: quantum correlations; discord; interferometry; quantum metrology

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APA (6th Edition):

Lang, M. D. (2015). Measures of Nonclassical Correlations and Quantum-Enhanced Interferometry. (Doctoral Dissertation). University of New Mexico. Retrieved from http://hdl.handle.net/1928/30398

Chicago Manual of Style (16th Edition):

Lang, Matthias Dominik. “Measures of Nonclassical Correlations and Quantum-Enhanced Interferometry.” 2015. Doctoral Dissertation, University of New Mexico. Accessed June 15, 2019. http://hdl.handle.net/1928/30398.

MLA Handbook (7th Edition):

Lang, Matthias Dominik. “Measures of Nonclassical Correlations and Quantum-Enhanced Interferometry.” 2015. Web. 15 Jun 2019.

Vancouver:

Lang MD. Measures of Nonclassical Correlations and Quantum-Enhanced Interferometry. [Internet] [Doctoral dissertation]. University of New Mexico; 2015. [cited 2019 Jun 15]. Available from: http://hdl.handle.net/1928/30398.

Council of Science Editors:

Lang MD. Measures of Nonclassical Correlations and Quantum-Enhanced Interferometry. [Doctoral Dissertation]. University of New Mexico; 2015. Available from: http://hdl.handle.net/1928/30398


University of New Mexico

3. Reichenbach, Iris Evelyn Nicole. Optical control and quantum information processing with ultracold alkaline-earth-like atoms.

Degree: Physics & Astronomy, 2010, University of New Mexico

Ultracold neutral atoms in optical lattices are rich systems for the investigation of many-body physics as well as for the implementation of quantum information processing. While traditionally alkali atoms were used for this research, in recent years alkaline-earth-like atoms have attracted considerable interest. This is due to their more complex but tractable internal structure and easily accessible transitions. Furthermore, alkaline-earth-like atoms have extremely narrow {}1S → {}3P intercombination transitions, which lend themselves for the implementation of next generation atomic clocks. In this dissertation, I show that exquisite control of alkaline-earth-like atoms can be reached with optical methods, and elucidate ways to use this controllability to further different aspects of research, mainly quantum information processing. Additionally, the control of alkaline-earth-like atoms is very interesting in many-body physics and the improvement of atomic clocks. Since heating usually degrades the performance of quantum gates, recooling of qubits is a necessity for the implementation of large scale quantum computers. Laser cooling has advantages over the usually used sympathetic cooling, given that it requires no additional atoms, which have to be controlled separately. However, for qubits stored in hyperfine states, as usually done in alkali atoms, laser cooling leads to optical pumping and therefore to loss of coherence. On the other hand, in the ground state, the nuclear spin of alkaline-earth-like atoms is decoupled from the electronic degrees of freedom. As I show in this dissertation, this allows for the storage of quantum information in the nuclear spin and laser cooling on the electronic degrees of freedom. The recooling protocol suggested here consists of two steps: resolved sideband cooling on the extremely narrow {}1S0 →  {}3P0 clock transition and subsequent quenching on the much shorter lived {}1P1 state. A magnetic field is used to overcome the hyperfine interaction in this excited state and thus ensures decoupling of the nuclear spin degrees of freedom during the quenching. The application of this magnetic field also allows for photon scattering on the {}1P1 state, while preserving the nuclear spin, e. g. for electronic qubit detection. The manipulation of the scattering properties of neutral atoms is an important aspect of quantum control. In contrast to alkali atoms, whose broad linewidths cause large losses, this can be done with purely optical methods via the implementation of an optical Feshbach resonance for alkaline-earth-like atoms. Here, the scattering length resulting from the application of an optical Feshbach resonance on the {}1S0 →  {}3P1 intercombination line, including hyperfine interaction and rotation is calculated for {}171Yb. Due to their different parities, the p-wave scattering length can be controlled independently from the s-wave scattering length, thus allowing for unprecedented control over the scattering properties of… Advisors/Committee Members: Deutsch, Ivan H., Caves, Carlton M., Prasad, Sudhakar, Evans, Deborah G., Julienne, Paul S..

Subjects/Keywords: Quantum computers – Materials; Atomic clocks – Materials; Optical resonance; Quantum optics; Ytterbium.

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Reichenbach, I. E. N. (2010). Optical control and quantum information processing with ultracold alkaline-earth-like atoms. (Doctoral Dissertation). University of New Mexico. Retrieved from http://hdl.handle.net/1928/10334

Chicago Manual of Style (16th Edition):

Reichenbach, Iris Evelyn Nicole. “Optical control and quantum information processing with ultracold alkaline-earth-like atoms.” 2010. Doctoral Dissertation, University of New Mexico. Accessed June 15, 2019. http://hdl.handle.net/1928/10334.

MLA Handbook (7th Edition):

Reichenbach, Iris Evelyn Nicole. “Optical control and quantum information processing with ultracold alkaline-earth-like atoms.” 2010. Web. 15 Jun 2019.

Vancouver:

Reichenbach IEN. Optical control and quantum information processing with ultracold alkaline-earth-like atoms. [Internet] [Doctoral dissertation]. University of New Mexico; 2010. [cited 2019 Jun 15]. Available from: http://hdl.handle.net/1928/10334.

Council of Science Editors:

Reichenbach IEN. Optical control and quantum information processing with ultracold alkaline-earth-like atoms. [Doctoral Dissertation]. University of New Mexico; 2010. Available from: http://hdl.handle.net/1928/10334

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