We investigate theoretically and experimentally the electron paramagnetic resonance (EPR) spectra of bismuth doped silicon (Si:Bi) at intermediate magnetic fields, B≈0.05−0.6 T. We identify a previously unexplored EPR regime of "cancellation-resonances"- where part of the hyperfine coupling is resonant with the external field-induced splitting. We show this regime has interesting and experimentally accessible consequences for spectroscopy and quantum information applications. These include reduction of decoherence, fast manipulation of the coupled nuclear-electron qubit system and line narrowing in the multi-qubit case. We test our theoretical analysis by comparing with experimental X-band (9.7 GHz) EPR spectra obtained in the intermediate field regime.
@article{arxiv.1004.3475,
title = {Bismuth in silicon qubits: the role of EPR cancellation resonances},
author = {M. H. Mohammady and G. W. Morley and T. S. Monteiro},
journal= {arXiv preprint arXiv:1004.3475},
year = {2010}
}