Electrical Control and Quantum Chaos with a High-Spin Nucleus in Silicon

Abstract

Nuclear spins are highly coherent quantum objects. In large ensembles, their control and detection via magnetic reso nance is widely exploited, e.g. in chemistry, medicine, materials science, and mining. Nuclear spins also prominently featured in early ideas and demonstrations of quantum information processing. In silicon, the high-fidelity coherent control of a single phosphorus (31-P) nuclear spin has led to record-breaking coherence times, as well as entangle ment and weak measurements. Replacing 31-P by a high-spin donor leverages all of these features, and unlocks a rich variety of experiments that probe quantum physics at a fundamental level. In this thesis, we demonstrate the coherent quantum control of a single antimony (123-Sb) donor atom, whose higher nuclear spin has eight nuclear spin states. However, rather than conventional nuclear magnetic resonance (NMR), we employ nuclear electric resonance (NER) to drive nuclear spin transitions using localized electric fields produced within a silicon nanoelectronic device. This method exploits an idea first proposed in 1961 but never realized experi mentally with a single nucleus, nor in a non-polar crystal such as silicon. Our results are quantitatively supported by a microscopic theoretical model that reveals how the purely electrical modulation of the nuclear electric quadrupole interaction results in coherent nuclear spin transitions. The spin dephasing time, 0.1 seconds, surpasses by orders of magnitude those obtained via methods thafrequire a coupled electron spin for electrical drive. The coherent control of an 123-Sb nucleus opens up the door to experiments on the foundations of quantum me chanics, such as the emergence of chaos in the quantum-classical transition. We present here a realistic proposal to construct a chaotic driven top from the 123-Sb nuclear spin. We show that signatures of chaos are expected to arise for experimentally realizable system parameters, allowing the study of the relation between quantum decoherence and classical chaos, and the observation of dynamical tunneling. These results show that high-spin quadrupolar nuclei could be deployed as chaotic models, strain sensors, and hybrid spin-mechanical quantum systems using all-electrical controls. Integrating electrically-controllable nuclei with quan tum dots could pave the way to scalable, nuclear-and electron-spin-based quantum computers in silicon that operate without the need for oscillating magnetic fields.Declaration relating to disposition of project thesis/dissertation I hereby grant to the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all property rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or-dissertation.I also authorise University Microfilms to use the 350 word...

Nuclear spin alignment of sodium ions via electric field gradients in phospholipid membranes

“…When considering Kramers' degeneracy theorem, which applies to systems with half-integer spins maintaining the time reversal symmetry, the quadrupole interaction inherently demonstrates a double degeneracy without the presence of other interactions. 6,7 This suggests that spins with opposite magnitudes possess equivalent energy levels. Therefore, whether the % V 33 axis points in the positive or negative direction of the z-axis, as depicted in Fig.…”

“…A recent study using electric field gradient (EFG) to control nuclear spins has highlighted the potential of nuclear electric resonance (NER). 6,7 Similar to nuclear magnetic resonance (NMR), for atomic nuclei with a nuclear spin greater than 1/2 which exhibit a non-zero electric quadrupole moment, the external EFG can also control the direction of its nuclear spin and energy level splitting. Considering a nuclear spin greater than 1/2 under the EFG environment, the EFG exerts a force and corresponding torque on the electric quadrupole moment, inducing a rotational motion of the quadrupole moment.…”