Browsing by Author "Hakonen, Pertti, Prof., Aalto University School of Science, Department of Applied Physics, Finland"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Harnessing Quantum Resources in Superconducting Devices for Computing and Sensing
    (Aalto University, 2024) Perelshtein, Mikhail; Teknillisen fysiikan laitos; Department of Applied Physics; NANO group (Quantum Circuits and Correlations); Perustieteiden korkeakoulu; School of Science; Hakonen, Pertti, Prof., Aalto University School of Science, Department of Applied Physics, Finland
    Quantum resources play a pivotal role in the emerging field of quantum technologies, underpinning the development of quantum computers, communication systems, and sensing devices with transformative capabilities beyond classical counterparts. In this thesis, key quantum resources, such as entanglement and coherency, are investigated with an emphasis on superconducting metamaterials, including Josephson Parametric Amplifiers, Travelling Wave Parametric Amplifiers, and artificial transmon atoms. The presented thesis strives to explore, unify, and harness the quantum resources in quantum sensing and computing tasks. The initial cluster of studies places a spotlight on the experimental preparation of quantum states enriched with quantum resources. The thesis presents the generation of multipartite quantum entanglement using innovative pump tone techniques applied to the Josephson parametric system, expanding the possibilities for microwave control of the entanglement structure and demonstrating for the first time genuine entanglement between four microwave modes. The generation of frequency-entangled photons with record-breaking 4 GHz frequency separation is presented for distributed Josephson metamaterial, highlighting the practical implications of entangled microwave photons in broadband quantum information processing. Besides, the thesis presents the protocol for preparation of multi-qubit states with target amplitudes, which features polylogarithmic scaling in the number of encoded parameters. The protocol demonstrates its effectiveness with large-scale circuits up to 100 qubits, which are studied numerically. The presented work advances phase estimation protocols for quantum sensing, optimizing resource utilization and sensitivity, particularly in the realm of magnetic field measurements. It further explores the effectiveness of separable and entangled states for magnetometry by conducting experiments on existing quantum hardware through cloud-based IBM quantum systems. A novel sensing algorithm for multi-level artificial atoms emerges from this exploration, designed to maximize the utilization of available quantum resources, which is numerically investigated. Finally, the thesis presents a study of the hybrid quantum algorithm for solving large linear systems of equations, showcases the current state of intermediate-scale quantum computers, and proposes the benchmark for future hardware developments. It introduces a classification scheme based on entanglement structure and successfully implements a record-breaking 217-dimensional problem on IBM quantum processors.