Experimental consequences of coherence in time

In this chapter we shall discuss the notion of coherence in time, and, in particular, describe in some detail the experiment of Lindner et al. (2005) in which it was demonstrated that an electron wave packet undergoing a sequential ionizing perturbation in time (from Argon gas) undergoes interference phenomena, and the careful analysis and design of an experiment by Palacios et al. (2009) to show that a two electron spin state could be formed coherentlyTwo electron spin state at different times from two electrons at different times. We explain that neither of these experiments can be understood consistently in the framework of standard nonrelativistic quantum theory (or its extension to the nonrelativistic Floquet theory (Floquet 1883)), but that the Stueckelberg-Horwitz-Piron theory can describe these phenomena in a simple way when the time intervals involved lie within the spread in time of the wave packets.