Shallow Donor Electron Spins as Qubits in Si and SiGe: a Pulsed ESR Study

X-band pulse electron spin resonance spectroscopy has been used to determine the characteristic phase memory time (TM) for phosphorous shallow donors in Si and Si1xGex (x=0.052) which have been proposed as qubits in group IV based quantum computing devices. With fast intense microwave pulses, electron spin echoes, formally equivalent to single-qubit operations, can be detected providing the characteristic times as well as additional information on the coupling between the electron spin and its surroundings (other electron or nuclear spins). The electron spin echo envelope modulation due to the super-hyperfine interaction with 29Si and 73Ge, has been detected in the Si and Si1xGex samples.