From Spectral Relaxation to Quantified Decoherence

Quantum information processing (QIP) requires thorough assessment of decoherence. Atoms or ions prepared for QIP often become addressed by radiation within schemes of alternating microwave-optical double resonance. A welldefined amount of decoherence may be applied to the system when spurious resonance light is admitted simultaneously with the driving radiation. This decoherence is quantified in terms of longitudinal and transverse relaxation. It may serve for calibrating observed decoherence as well as for testing errorcorrecting quantum codes.