Contact between laboratory instruments and equations of quantum   mechanics
  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. 
John M. Myers and F. Hadi Madjid