It is demonstrated that Eberly and Singh’s notion of partial stationarity of a quantum system can be reconciled with Mandelstam and Tamm’s approach to deriving energy-time inequalities. The result of this merger is an improved stationarity time, which provides a more precise measure of the degree of stationarity of the system under study, and which permits a sharper statement of the energy-time uncertainty relation than that given by Eberly and Singh.

• Received 20 August 1984

DOI:https://doi.org/10.1103/PhysRevA.31.483