dc.contributor.author 
Clark, Craig R. 
en_US 
dc.date.accessioned 
20120606T16:54:11Z 

dc.date.available 
20120606T16:54:11Z 

dc.date.issued 
20120106 
en_US 
dc.identifier.uri 
http://hdl.handle.net/1853/43757 

dc.description.abstract 
Lasercooled atomic ions have led to an unprecedented amount of control over the quantum states of matter. The Coulombic interaction allows for information to be transferred between neighboring ions, and this interaction can be used to entangle qubits for logic operations in quantum information processors. The same procedure for logic operations can be used for high resolution atomic spectroscopy, and is the basis for the most accurate atomic optical clocks to date. This thesis describes how lasercooled atomic ions can impact physical chemistry through the development of molecular ion spectroscopy techniques and the simulation of magnetic systems by ion trap quantum computers.
A new technique developed for spectroscopy, Sympathetic Heating Spectroscopy (SHS), takes advantage of the Coulombic interaction between two trapped ions: the control ion and a spectroscopy ion. SHS uses the back action of the interrogating laser to map spectroscopy ion information onto the Doppler shift of the control ion for measurement. SHS only requires Doppler cooling of the ions and fluorescence measurement and represents a simplification of quantum logic spectroscopy. This technique is demonstrated on two individual isotopes of calcium: Ca40(+) for cooling and Ca44(+) as the spectroscopy ion.
Having demonstrated SHS with atomic ions, the next step was to extend the technique by loading and characterizing molecular ions. The identification of an unknown molecular ion is necessary and can be achieved by monitoring the change in motion of the two ion crystal, which is dependent on the molecular ion mass. The motion of two trapped ions is described by their normal modes, which can be accurately measured by performing resolved sideband spectroscopy of the S(1/2)D(5/2) transition of calcium. The resolved sidebands can be used to identify unknown ions (atomic and molecular) by calculating the mass based on the observed value in axial normal mode frequencies. Again, the trapped molecular ion is sympathetically cooled via the Coulombic interaction between the Ca40(+) and the unknown molecular ion. The sensitivity of SHS could be improved by implementing sympathetic sideband cooling and determining the heating by measuring single quanta of motion.
The ultimate limit of control would be the development of an ion trap quantum computer. Many theoretical quantum computing researchers have made bold claims of the exponential improvement a quantum computer would have over a classical computer for the simulation of physical systems such as molecules. These claims are true in principle for ideal systems, but given nonideal components it is necessary to consider the scaling due to error correction. An estimate of the resource requirements, the total number of physical qubits and computational time, required to compute the ground state energy of a 1D quantum Transverse Ising Model (TIM) of N spin1/2 particles, as a function of the system size and the numerical precision, is presented. This estimate is based on analyzing the impact of faulttolerant quantum error correction in the context of the quantum logic array architecture. The results show that a significant amount of error correction is required to implement the TIM problem due to the exponential scaling of the computational time with the desired precision of the energy. Comparison of this result to the resource requirements for a faulttolerant implementation of Shor's quantum factoring algorithm reveals that the required logical qubit reliability is similar for both the TIM problem and the factoring problem. 
en_US 
dc.publisher 
Georgia Institute of Technology 
en_US 
dc.subject 
Ion trap 
en_US 
dc.subject 
Spectroscopy 
en_US 
dc.subject 
Quantum computing 
en_US 
dc.subject 
Atomic and molecular physics 
en_US 
dc.subject 
Chemistry 
en_US 
dc.subject.lcsh 
Trapped ions 

dc.subject.lcsh 
Ions 

dc.subject.lcsh 
Quantum theory 

dc.subject.lcsh 
Chemistry, Physical and theoretical 

dc.title 
Sympathetic heating and cooling of trapped atomic and molecular ions 
en_US 
dc.type 
Dissertation 
en_US 
dc.description.degree 
PhD 
en_US 
dc.contributor.department 
Chemistry and Biochemistry 
en_US 
dc.description.advisor 
Committee Chair: Kenneth R. Brown; Committee Member: Alex Kuzmich; Committee Member: David Sherrill; Committee Member: JeanLuc Bredas; Committee Member: Richart Slusher 
en_US 