HIDDEN AND UNHIDDEN INFORMATION IN QUANTUM TUNNELING

We discuss the claim that when the peak of a tunneling wave packet app ears on the far side of a barrier sooner than would be allowed by caus al propagation of the incident peak, this must be interpreted to mean that the transmitted particles originate toward the leading edge of th e incident peak. We examine the status of information about where in a wave packet a particle is, both in terms of Bohm's deterministic pict ure of quantum mechanics and in terms of a recently proposed Gedanken experiment. We find that while there are very real senses in which thi s interpretation makes sense, attempts to explicitly bring out this ex tra information in the form of quantum-mechanical observables necessar ily fail. It therefore remains ''hidden'' information, which we can de duce indirectly from multiple experiments or from the principle of cau sality, but which we can never observe directly in a single experiment .