Development of single ion detectors for semiconductor quantum devices

Recent results in quantum computing, such as Google achieving quantum supremacy, have made it clear that we are well within the noisy intermediate scale quantum (NISQ) computing regime. Whilst this enables the probing of quantum phenomena and the development of simple quantum algorithms, practical large-scale quantum computing is going to require millions of physical qubits to be constructed on an industrial scale. Silicon donor qubits are one of the most promising candidates for realising this immense technical challenge. Their long coherence times, well established read-out and control mechanisms make each qubit an excellent candidate to form the needed physical qubits. Combining this with architectures to couple these qubits with each other, compatibility with CMOS semiconductor fabrication processes and small physical size means that silicon donor qubits are perfectly placed to become the qubit system of the future. One crucial factor still needed for the large-scale development of donor qubits is a system that enables the deterministic placement of individual donors in the silicon lattice. Developed in the field of high-energy physics, semiconductor detectors can detect ionising radiation impacting the chip. In this thesis we present the progress that has been made in developing custom silicon detectors that can detect the implantation of a single ion for the purposes of quantum computing. We study different process steps and their impact on detector performance, paving a way for more sophisticated and reliable detectors. Also presented are several proposed experiments and design changes predicted to improve detector performance or the ease of integration with donor qubit devices. These improvements are crucial elements in forming functional silicon detectors that can be integrated with existing qubit architectures to build future large-scale quantum computers. Ion implantation allows the introduction of any group-V donor into the silicon crystal, giving us the choice of donor species best suited for quantum computing. Using 123Sb as the donor to perform quantum computing allows us to leverage a completely new control mechanism via nuclear electric resonance (NER). This thesis will also cover modelling work undertaken to verify and validate the understanding of what electrical effects cause NER to happen

Exploring quantum chaos with a single nuclear spin

Most classical dynamical systems are chaotic. The trajectories of two identical systems prepared in infinitesimally different initial conditions diverge exponentially with time. Quantum systems, instead, exhibit quasi-periodicity due to their discrete spectrum. Nonetheless, the dynamics of quantum systems whose classical counterparts are chaotic are expected to show some features that resemble chaotic motion. Among the many controversial aspects of the quantum-classical boundary, the emergence of chaos remains among the least experimentally verified. Time-resolved observations of quantum chaotic dynamics are particularly rare, and as yet unachieved in a single particle, where the subtle interplay between chaos and quantum measurement could be explored at its deepest levels. We present here a realistic proposal to construct a chaotic driven top from the nuclear spin of a single donor atom in silicon, in the presence of a nuclear quadrupole interaction. This system is exquisitely measurable and controllable, and possesses extremely long intrinsic quantum coherence times, allowing for the observation of subtle dynamical behavior over extended periods. We show that signatures of chaos are expected to arise for experimentally realizable parameters of the system, allowing the study of the relation between quantum decoherence and classical chaos, and the observation of dynamical tunneling.Comment: revised and published versio

Coherent control of NV- centers in diamond in a quantum teaching lab

The room temperature compatibility of the negatively-charged nitrogen-vacancy (NV-) in diamond makes it the ideal quantum system for a university teaching lab. Here, we describe a low-cost experimental setup for coherent control experiments on the electronic spin state of the NV- center. We implement spin-relaxation measurements, optically-detected magnetic resonance, Rabi oscillations, and dynamical decoupling sequences on an ensemble of NV- centers. The relatively short times required to perform each of these experiments (<10 minutes) demonstrate the feasibility of the setup in a teaching lab. Learning outcomes include basic understanding of quantum spin systems, magnetic resonance, the rotating frame, Bloch spheres, and pulse sequence development.Comment: 16 pages, 9 figure

Observing hyperfine interactions of NV centers in diamond in an advanced quantum teaching lab

The negatively charged nitrogen-vacancy (NV$^-$) center in diamond is a model quantum system for university teaching labs due to its room-temperature compatibility and cost-effective operation. Based on the low-cost experimental setup that we have developed and described for the coherent control of the electronic spin (Sewani et al.), we introduce and explain here a number of more advanced experiments that probe the electron-nuclear interaction between the \nv electronic and the \NN~and \CC~nuclear spins. Optically-detected magnetic resonance (ODMR), Rabi oscillations, Ramsey fringe experiments, and Hahn echo sequences are implemented to demonstrate how the nuclear spins interact with the electron spins. Most experiments only require 15 minutes of measurement time and can, therefore, be completed within one teaching lab.Comment: Extension of the teaching lab experiments described in Sewani et al., Coherent control of NV centers in diamond in a quantum teaching lab. American Journal of Physics 88, 1156 (2020). https://doi.org/10.1119/10.000190