High Field Phenomena of Qubits

TL;DR

This paper explores high magnetic field effects on solid state spin systems like Si:P, SiC:N, and diamond centers, revealing phenomena that enhance qubit initialization, coherence, and readout for quantum computing.

Contribution

It demonstrates how high magnetic fields induce new effects in spin-based qubits, improving their initialization, coherence times, and readout mechanisms in solid state systems.

Findings

High magnetic fields enable better spin initialization at low temperatures.

Decoherence due to dipolar interactions can be reduced with high fields.

New mechanisms for electrical readout of electron spins are observed.

Abstract

Electron and nuclear spins are very promising candidates to serve as quantum bits (qubits) for proposed quantum computers, as the spin degrees of freedom are relatively isolated from their surroundings, and can be coherently manipulated e.g. through pulsed EPR and NMR. For solid state spin systems, impurities in crystals based on carbon and silicon in various forms have been suggested as qubits, and very long relaxation rates have been observed in such systems. We have investigated a variety of these systems at high magnetic fields in our multi-frequency pulsed EPR/ENDOR spectrometer. A high magnetic field leads to large electron spin polarizations at helium temperatures giving rise to various phenomena that are of interest with respect to quantum computing. For example, it allows the initialization of the both the electron spin as well as hyperfine-coupled nuclear spins in a well defined state by combining millimeter and RF radiation; it can increase the T2 relaxation times by eliminating decoherence due to dipolar interaction; and it can lead to new mechanisms for the coherent electrical readout of electron spins. We will show some examples of these and other effects in Si:P, SiC:N, and nitrogen-related centers in diamond.