Thesis (Ph. D.)--Drexel University, 2006. / Includes abstract. Includes bibliographical references (leaves 167-176).

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

No description available.

archives@tulane.edu / 1 / Sanjaya Lohani

No description available.

Trapping ultracold atoms in optical lattices enabled the study of strongly correlated phenomena in an environment that is far more controllable and tunable than what was possible in condensed matter. Here, we consider coupling these systems to quantised light where the quantum nature of both the optical and matter fields play equally important roles in order to push the boundaries of what is possible in ultracold atomic systems. We show that light can serve as a nondestructive probe of the quantum state of matter. By considering a global measurement we show that it is possible to distinguish a highly delocalised phase like a superfluid from the Bose glass and Mott insulator. We also demonstrate that light scattering reveals not only density correlations, but also matter-field interference. By taking into account the effect of measurement backaction we show that the measurement can efficiently compete with the local atomic dynamics of the quantum gas. This can generate long-range correlations and entanglement which in turn leads to macroscopic multimode oscillations across the whole lattice when the measurement is weak and correlated tunnelling, as well as selective suppression and enhancement of dynamical processes beyond the projective limit of the quantum Zeno effect in the strong measurement regime. We also consider quantum measurement backaction due to the measurement of matter-phase-related variables such as global phase coherence. We show how this unconventional approach opens up new opportunities to affect system evolution and demonstrate how this can lead to a new class of measurement projections thus extending the measurement postulate for the case of strong competition with the system's own evolution.

<p dir="ltr">As the design of computer chips heavily relies on computer simulations, it is envisioned that numerical modeling will play an increasingly important role in the development of unconventional computing technologies. This thesis studies the computational frameworks related to the development of unconventional computing, including probabilistic computing and quantum computing. The capability of probabilistic computing in solving NP-complete number theory problems is demonstrated. Generalized Helmholtz decomposition is shown as a theoretical basis for quantization of electromagnetic fields via numerical mode decomposition. A 2D demonstration of numerical quantization with finite difference method is presented. A computational framework amenable to integral equation solver is proposed to investigate the scattering effect on momentum-entangled photons from spontaneous parametric downconversion. A generic model to investigate field-matter interaction with nonlinearity is presented.</p>

Strong effective photon-photon interactions mediated by atom-photon couplings have been routinely achievable in QED setups for some time now. Recently, there have been several proposals to push the physics of interacting photons into many- body distributed architectures. The essential idea is to coherently couple together arrays of QED resonators, such that photons can hop between resonators while interacting with each other inside each resonator. These proposed structures have attracted intense theoretical attention while simultaneously inspiring experimental efforts to realise this novel regime of strongly-correlated many-body states of light. A central challenge of both theoretical and practical importance is to understand the physics of such coupled resonator arrays (CRAs) beyond equilibrium, when unavoidable (or sometimes even desired) photon loss processes are accounted for. This thesis presents several studies whose purpose can roughly be divided in two aims. The first part studies just what constitutes a valid physical and computational representation of non-equilibrium driven-dissipative CRAs. Addressing these ques- tions constitutes essential groundwork for further investigations of CRA phenomena, as numerical experiments are likely to guide and interpret near-future experimen- tal array observations. The relatively small body of existing work on CRAs out of equilibrium has often truncated their full, rich physics. It is important to establish the effects and validity of these approximations. To this end we introduce powerful numerical algorithms capable of efficiently simulating the full dynamics of CRAs, and use them to characterise the non-equilibrium steady states of arrays reached under the combined influence of dissipation and pumping. Having established the rigour necessary to realistically describe CRAs, we exam- ine two novel phenomena observable in near-future small arrays. Firstly we relate a counter-intuitive ‘super bunching’ in the statistics of photons emitted from arrays engineered to demonstrate strong effective photon-photon repulsion at the single and two-photon level, to an interplay between the underlying eigen-structure and details of the non-equilibrium operation. Secondly we characterise a dynamical phenomenon in which domains of ‘frozen’ photons remain trapped in sufficiently nonlinear arrays. Finally we present a preliminary characterisation of a previously unexplored phase diagram of arrays under coherent two-photon pumping. Com- petition between the coherence injected by the pumping, photon interactions and delocalisation processes lead to interesting new physical signatures.

Light, when reduced to the level of individual quanta, can possess, besides its familiar properties of wavelength, direction, and polarization, a set of correlations irreducible to classical correlations, among other peculiar behaviour. These correlated states are intrinsically interesting, and are also useful for quantum-enhanced information processing. In this thesis, I use a high-bandwidth, far-off-resonant Raman memory to implement two quantum information primitives -- entanglement generation and light storage -- at room temperature and ambient conditions. Specifically, I show, for the first time, the entanglement of two solid-state objects at room temperature and, also, the storage of light in a hollow-core optical fibre. In the first part, I show that the optical phonon modes of two diamonds can be entangled -- the prototypical non-classical correlation -- at room temperature. The entanglement was generated by spontaneous Raman scattering with projective measurements using single-photon detectors. The degree of entanglement was rigorously quantified by measuring the concurrence -- an entanglement monotone -- of the joint state of the scattered optical fields. In the second part, I store light in the coherent superposition of cesium atoms confined within a kagome-structured hollow-core photonic crystal fibre at room temperature using a far-off-resonant stimulated Raman interaction. The storage efficiency of the memory was 27$pm$1% and the noise level was sufficiently low such that single-photon-level pulses could be stored. Taken together, these results highlight the potential of Raman memories for quantum information tasks in noisy systems with short coherence times.

QC 351 A7 no. 66 / This volume is intended to be used as a text for two courses at the Optical Sciences Center. A major part of the volume consists of lecture notes on the theory of laser operation, written by M. O. Scully and M. Sargent III. These notes, developed under NSF sponsorship for a new quantum optics curriculum at the University of Arizona, were the basis of a new course "Quantum Optics," which was first offered during the 1969-70 academic year. After considerable editing they were again used during "The Physics of Quantum Electronics" summer course in Prescott, June 22 - July 3, 1970. The remainder of the volume consists of unpublished work presented at Prescott, most of which will be utilized in a new course on nonlinear optics. References are given to material presented that has already appeared in print.