THERMODYNAMICS OF QUANTA IN A SINGLE TRAPPED ION AND EXCHANGING MOTIONAL QUANTA BETWEEN IONS IN SEPARATE TRAPS VIA A NEARBY CONDUCTING WIRE

Abstract

This thesis begins with a project on the implementation of a quantum thermodynamic cycle using a single ion. We examine a single-atom energy-conversion device with a quantum load. The experimentally-backed study uses cyclic operations involving superpositions of the ion’s internal states, periodically coupled to the ion’s motional states. We show that the ergotropy of the ion’s motional state distribution can increase despite the increase of its entropy, making the atom a toy model for a quantum battery. Experiments on the thermodynamics of quantum systems help improve our basic understanding of few-body systems operating in the quantum regime. After the study in quantum thermodynamics I move on to a purely theoretical study on designing systems for trapped charged atoms (ions) to interact optimally with nearby conductors. The main subject explored is how to use a conducting wire to transfer a quantum bit (qubit) of information from an ion in one trap to another ion in a separate trap by coupling the two ions’ motional (phonon) states. Optimizing the design for the coupling system allows quantum information to be exchanged with a time t_ex. more than ten times shorter than the information decay time t_deco. Effects of 1/f (Anomalous) surface heating noise are included in t_deco., using aggregate and recent experimental findings to justify analytical expressions for the heating rate dn/dt of a trapped ion and its motional state decoherence time t_deco. With carefully chosen parameter values I find no barriers to exchanging quantum information between ion qubits in separate surface traps using a conducting wire. Moreover, this should be possible using existing technologies and materials, and singly-charged ions. The final chapter describes limitations of a previous approach to describe the interaction of trapped ions with nearby conductors using equivalent circuit elements. It gives an alternative modular treatment which may be useful for troubleshooting real experimental designs. The two chapters on ions interacting with nearby conductors are applicable in the near term for the development of trapped ion quantum computers, and possible future quantum thermodynamics experiments.