Quantum computing gives novel way of computing using quantum mechanics, which furthers human knowledge and has exciting applications. Quantum systems with diluted spins such as rare earth ions hosted in single crystal, molecule-based magnets etc. are promising qubits candidates to form the basis of a quantum computer. High sensitivity measurement and coherent control of these spin systems are crucial for their practical usage as qubits. The micro-SQUID (direct-current micrometer-sized Superconducting QUantum Interference Device) is capable to measure magnetization of spin system with high sensitivity. For example, the micro-SQUID technique can measure magnetic moments as small as several thousand μB as shown by the study of [W. Wernsdorfer, Supercond. Sci. Technol. 22, 064013 (2009)]. Here we develop a novel on-chip setup that combines the micro-SQUID sensitivity with microwave excitation. Such setup can be used for electron spin resonance measurements or coherent control of spins utilizing the high sensitivity of micro-SQUID for signal detection. To build the setup, we studied the fabrication process of the micro-SQUID, which is made of weak-linked Josephson junctions. The SQUID as a detector is integrated on the same chip with a shorted coplanar waveguide, so that the microwave pulses can be applied through the waveguide to excite the sample for resonance measurements. The whole device is plasma etched from a thin (∼20nm) niobium film, so that the SQUID can work at in large in-plane magnetic fields of several tesla. In addition, computer simulations are done to find the best design of the waveguide such that the microwave excitation field is sufficiently strong and uniformly applied to the sample. The magnetization curve of Mn₁₂ molecule-based magnet sample is measured to prove the proper working of the micro-SQUID. Electron spin resonance measurement is done on the setup for gadolinium ions diluted in a CaWO₄ single crystal. The measurement shows clear evidence of the resonance signal from the 1st transition of the gadolinium ions' energy levels, which shows the setup is successfully built. Due to the high sensitivity of micro-SQUID and the ability to concentrate microwave energy in small areas of the chip, this setup can detect signals from a small number of spins (10⁷) in a small volume (several μm³). / A Dissertation submitted to the Department of Physics in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester 2017. / June 28, 2017. / Resonance, SQUID, waveguide / Includes bibliographical references. / Irinel Chiorescu, Professor Directing Dissertation; Naresh Dalal, University Representative; Laura Reina, Committee Member; Pedro Schlottmann, Committee Member; Peng Xiong, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_552155 |
| Contributors | Yue, Guang (authoraut), Chiorescu, Irinel (professor directing dissertation), Dalal, Naresh S. (university representative), Reina, Laura (committee member), Schlottmann, Pedro U. (committee member), Xiong, Peng (committee member), Florida State University (degree granting institution), College of Arts Sciences (degree granting college), Department of Physics (degree granting departmentdgg) |
| Publisher | Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text, doctoral thesis |
| Format | 1 online resource (123 pages), computer, application/pdf |
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