Engineering Scalable Quantum Systems From First-Principles to Large-Scale Control

Abstract

Color centers in solids are promising platforms for quantum communication, sensing, and computing, featuring highly coherent optical transitions, as well as native electron and nuclear spins that can be used as quantum memories. Existing state-of-the-art demonstrations have shown that multi-qubit control, spin-photon entanglement, and heralded entanglement are possible with devices consisting of a few color centers. However, the path to scaling the number of color centers integrated in these devices to the thousands or millions needed for advanced quantum networking and computing applications remains unclear. In particular, the requirement for highly coherent quantum operations both necessitates operation at cryogenic temperatures, and precise classical control signals delivered to each color center. Precise qubit control greatly increases the system complexity, while the cryogenic operation limits the amount of power that the system can dissipate. Both factors severely limit the number of color centers that can realistically be included in a single device using existing methods. This work will tackle the scaling problem from a system-level perspective from two directions. Firstly, I will quantify performance trade-offs between coherence, temperature, and optical properties of the group-IV color centers. A novel color center system, the ¹¹⁷SnV⁻ hyperfine color center, will be presented and its advantages compared to traditional group-IV color centers will be explored. Secondly, a method to integrate color centers with application specific integrated circuit (ASICs) will be demonstrated. The ASICs provides multiplexed control signals and increased control field efficiency, thus decreasing both the wiring complexity and thermal load per qubit. This work will thus pave the way to color center-based devices in which the number of qubits is not limited by the complexity or power dissipation of the control system.