Measurement and Control of Electron Spins in the Solid State with High Sensitivity

Spin-based solid-state quantum technology is one of the most promising research fields today, with experts anticipating its pivotal role in practical applications such as quantum sensing, quantum computation, and quantum communication. This technology exploits unique quantum mechanical properties, such as the entanglement and superposition of electron and nuclear spins, for practical implementation.

Electron spin resonance (ESR) and nuclear magnetic resonance (NMR) are the most straightforward methods for addressing, manipulating, and reading out the states of a large number of spins, often in the billions. However, these techniques lack the sensitivity required for quantum technology, which frequently demands manipulation and readout capabilities at the single-spin level. As a result, current spin-based quantum technological devices rely on either optical or electrical spin detection schemes capable of single-spin operation. These methods, however, are either limited to a small number of spin species that support optical detection or require complex strain-inducing nano/micro-fabricated constructs. Such limitations restrict the spin-sensing capabilities of these systems and present significant challenges to their scalability as useful quantum technological devices.

The primary goal of our research was to develop novel microresonators combined with low-noise spin detection devices for ESR measurements and the control of a small number of spins, operating at fields of approximately 1.2 and 3.4 T (~35 and 94 GHz resonance frequencies), for potential future use in quantum technology, addressing some of the aforementioned restrictions.

In this seminar, I will present a class of four high-sensitivity surface resonators, known as “ParPar” resonators, at the Q band (~35 GHz) and demonstrate that spin sensitivity improves as the dielectric constant increases. This conclusion is supported by additional results from 2D Fourier imaging of P1 centers in single-crystal diamond. Furthermore, I will present our work with high-sensitivity ParPar surface resonators at the W band (~95 GHz), which, for the first time, also integrates a cryogenic low-noise amplifier into the setup. I will show how spin sensitivity and power conversion efficiency improve when the frequency and magnetic field are increased, and the temperature is decreased.