Quantum-nondemolition measurement of the vibrational energy of a trapped ion
F. E. Harrison, A. S. Parkins, Matthew J. Collett, Daniel F. Walls · Physical Review A · 1997
A quantum-nondemolition (QND) measurement of the vibrational energy of a trapped ion may be made by placing it at a node of a cavity optical standing wave. In certain parameter regimes there is a backaction evading coupling between the ion's vibrational energy eigenstates and the coherent states of the cavity field. This facilitates a QND measurement of the ion trap state via a homodyne measurement on the cavity output field. This scheme has the advantage that the required measurements minimally disturb the ion.