  Ambiguity in the contact between laboratory instruments and equations of
quantum mechanics is formulated in terms of responses of the instruments to
commands transmitted to them by a Classical digital Process-control Computer
(CPC); in this way instruments are distinguished from quantum-mechanical models
(sets of equations) that specify what is desired of the instruments. Results
include: (1) a formulation of quantum mechanics adapted to computer-controlled
instruments; (2) a lower bound on the precision of unitary transforms required
for quantum searching and a lower bound on sample size needed to show that
instruments implement a desired model at that precision; (3) a lower bound on
precision of timing required of a CPC in directing instruments; (4) a
demonstration that guesswork is necessary in ratcheting up the precision of
commands.
