Browsing by Subject "Quantum information"

Now showing 1 - 3 of 3

Geometry of quantum noise
(2010-05) Dixit, Kuldeep Narayan; Sudarshan, E. C. G.; Markert, John; Paban, Sonia; De La Llave, Rafael; Bohm, Arno
Open quantum systems refer to systems that are affected by interaction with the environment. The effects of these unwanted interactions, called \emph{quantum noise}, are studied using dynamical maps. We study the geometry of these maps in this work. We review the canonical representations of dynamical maps such as reduced dynamics, $\mathcal{A}$ and $\mathcal{B}$ forms and operator sum representation. We develop a framework for simplifying the action of dynamical maps in terms of their action on the coherence vector associated with the density matrix. We use the framework to describe the geometry of depolarization, dephasing and dissipation in the domain of complete positivity. We give a geometric picture of how two-, three- and four-level systems are affected by these common forms of quantum noises. We show useful similarities between two- and four-level depolarizing maps and give a generalization for $n$-qubits. We also derive important results that restrict dephasing and dissipation.
Information, chaos, and thermodynamic notions in quantum systems
(2022-07-29) Guglielmo, Tyler; Fischler, Willy; Paban, Sonia; Caceres, Elena; Kilic, Can; Flauger, Raphael
This dissertation consists of four chapters. The first broadly and briefly orients the reader through an introduction to information spreading in quantum Ising systems, classical chaos, and entanglement in holographic settings. The next three chapters correspond to distinct lines of research conducted during my time as a graduate student, chosen for their thematic relation to information, information dynamics, chaos, and entanglement entropy. Chapter two is based on work conducted with Stefan Eccles, Willy Fischler, Juan Pedraza, and Sarah Racz, studying the spread of information in non-local quantum Ising systems [23]. Chapter three is based on work with Willy Fischler and Phuc Nugyen, studying chaos in a non-commutative field theory [29]. Chapter four is based on work with Phuc Nugyen, testing volume law entanglement in a holographic boosted black hole setting [38].
Trapping Ca⁺ inside a molecular cavity : a computational study of the potential energy surfaces for Ca⁺-[n]cycloparaphenylene, n=5-12
(2022-08-09) Allen, Cole Dempsey; Webb, Lauren J.
Ion trap quantum computing utilizes electronic states of atomic ions such as Ca⁺ to encode information on to a qubit. To explore the fundamental properties of Ca⁺ inside molecular cavities, we describe here a computational study of Ca⁺ bound inside neutral [n]-cycloparaphenylenes (n=5-12), often referred to as "nanohoops". This ab initio study characterizes optimized structures, harmonic vibrational frequencies, potential energy surfaces, and ion molecular orbital distortion as functions of increasing nanohoop size. The results of this work provide a first step in guiding experimental studies of the spectroscopy of these ion-molecular cavity complexes.