  Generally a central role has been assigned to an unavoidable physical
interaction between the measuring instrument and the physical entity measured
in the change in the wave function that often occurs in measurement in quantum
mechanics. A survey of textbooks on quantum mechanics by authors such as Dicke
and Witke (1960), Eisberg and Resnick (1985), Gasiorowicz (1974), Goswami
(1992), and Liboff (1993) supports this point. Furthermore, in line with the
view of Bohr and Feynman, generally the unavoidable interaction between a
measuring instrument and the physical entity measured is considered responsible
for the uncertainty principle. A gedankenexperiment using Feynman's double-hole
interference scenario shows that physical interaction is not necessary to
effect the change in the wave function that occurs in measurement in quantum
mechanics. Instead, the general case is that knowledge is linked to the change
in the wave function, not a physical interaction between the physical existent
measured and the measuring instrument. Empirical work on electron shelving that
involves null measurements, or what Renninger called negative observations
(Zeitschrift fur Physik, vol. 158, p. 417), supports these points. Work on
electron shelving is reported by Dehmelt and his colleagues (Physical Review
Letters, vol. 56, p. 2797), Wineland and his colleagues (Physical Review
Letters, vol. 57, p. 1699), and Sauter, Neuhauser, Blatt, and Toschek (Physical
Review Letters, vol. 57, p. 1696).
