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Electron spins are an attractive candidate for an implementation of quantum information processing (QIP) due to high polarization, fast control and long coherence times. Control in electron spin resonance benefits from extensive experience in liquid-state nuclear magnetic resonance QIP, and microwave and RF technology from industry. This thesis details the design and construction of an electron spin resonance spectrometer specifically for research in quantum information processing, including the microwave electronics and variable temperature resonators and probes. We also begin to evaluate our spectrometer using a novel technique known as randomized benchmarking which extracts a figure of merit relevant to QIP.

Electron spins are an attractive candidate for an implementation of quantum information processing (QIP) due to high polarization, fast control and long coherence times. Control in electron spin resonance benefits from extensive experience in liquid-state nuclear magnetic resonance QIP, and microwave and RF technology from industry. This thesis details the design and construction of an electron spin resonance spectrometer specifically for research in quantum information processing, including the microwave electronics and variable temperature resonators and probes. We also begin to evaluate our spectrometer using a novel technique known as randomized benchmarking which extracts a figure of merit relevant to QIP.

No description available.

No description available.

No description available.

A new versatile computer controlled electrochemlcal/ESR data acquisition system has been developed for the Investigation of short-lived radicals with life-times of 20 milliseconds and greater, Different computer programs have been developed to monitor the decay of radicals; over hours or minutes, seconds or milliseconds. Signal averaging and Fourier smoothing is employed in order to improve the signal to noise ratio. Two microcomputers are used to control the system, one home-made computer containing the M6800 chip which controls the magnetic field, and an IBM PC XT which controls the electrochemistry and the data acquisition. The computer programs are written in Fortran and C, and call machine language subroutines, The system functions by having the radical generated by an electrochemical pulse: after or during the pulse the ESR data are collected. Decaying radicals which have half-lives of seconds or greater have their spectra collected in the magnetic field domain, which can be swept as fast as 200 Gauss per second. The decay of the radicals in the millisecond region is monitored by time-resolved ESR: a technique in which data is collected in both the time domain and in the magnetic field domain. Previously, time-resolved ESR has been used (without field modulation) to investigate ultra-short-lived species with life-times in the region of only a few microseconds. The application of the data acquisition system to chemical systems is illustrated. This is the first time a computer controlled system whereby the radical is generated by electrochemical means and subsequently the ESR data collected, has been developed.

ESR quantum computing presents faster means to perform gates on nuclear spins than the traditional NMR methods. This means ESR is a test-bed that can potentially be useful in ways that are not possible with NMR. The first step is to demonstrate universal control in the ESR system. This work focuses on spin systems with one electron spin and two nuclear spins. We try to demonstrate control over the nuclear spins using the electron as an actuator. In order to perform the experiments, a customized ESR spectrometer was built in the lab. The main advantage of the home-built system is the ability to send arbitrary pulses to the spins. This ability is the key to perform high fidelity controls on the spin system. A customized low temperature probe was designed and built to have three features necessary for the experiments. First, it is possible to orient the sample, thus to change the spin Hamiltonian of the system, in situ. Second, the combined system is able to perform ESR experiments at liquid nitrogen and liquid helium temperatures and rotate the sample while it is cold. Last, the pulse bandwidth of the microwave resonator, which directly affects the fidelity of the gates, is held constant with respect to the sample temperature. Simulations of the experiments have been carried out and the results are promising. Preliminary experiments have been performed, the final set of experiments, demonstrating full quantum control of a three-spin system, are underway at present.

ESR quantum computing presents faster means to perform gates on nuclear spins than the traditional NMR methods. This means ESR is a test-bed that can potentially be useful in ways that are not possible with NMR. The first step is to demonstrate universal control in the ESR system. This work focuses on spin systems with one electron spin and two nuclear spins. We try to demonstrate control over the nuclear spins using the electron as an actuator. In order to perform the experiments, a customized ESR spectrometer was built in the lab. The main advantage of the home-built system is the ability to send arbitrary pulses to the spins. This ability is the key to perform high fidelity controls on the spin system. A customized low temperature probe was designed and built to have three features necessary for the experiments. First, it is possible to orient the sample, thus to change the spin Hamiltonian of the system, in situ. Second, the combined system is able to perform ESR experiments at liquid nitrogen and liquid helium temperatures and rotate the sample while it is cold. Last, the pulse bandwidth of the microwave resonator, which directly affects the fidelity of the gates, is held constant with respect to the sample temperature. Simulations of the experiments have been carried out and the results are promising. Preliminary experiments have been performed, the final set of experiments, demonstrating full quantum control of a three-spin system, are underway at present.

<P> Single crystals of Zn2P207 containing 0.1% by weight of manganese impurity or 0.04% by weight of copper impurity were studied by means of electron spin resonance techniques from room temperature up to about 200°c. </p> <P> The existence of a phase transition at about 132°C in Zn2P2O7 was confirmed and a new phase, existing between 132°C and 155°C was found. The space group of the unit cell in this phase was deduced from the esr measurements. The spin Hamiltonian parameters were measured in the three phases and a discussion of their significance in terms of current theories of the zero field splitting of the ground state of S-state ionsis given. </p> / Thesis / Doctor of Philosophy (PhD)