While it is known that copying a quantum system does not increase the amoun
t of information obtainable about the originals, it may increase the amount
available in practice, when one is restricted to imperfect measurements. W
e present a detection scheme which, using imperfect detectors and possibly
noisy quantum copying machines (that entangle the copies), allows one to ex
tract more information from an incoming signal than with the imperfect dete
ctors alone. The case of single-photon detection with noisy,inefficient det
ectors and copiers (single controlled-NOT gates in this case) is investigat
ed in detail. The improvement in distinguishability between a photon and va
cuum is found to occur for a wide range of parameters, and to be quite robu
st to random noise. The properties that a quantum-copying device must have
to be useful in this scheme are investigated.