  We present a class of fast quantum algorithms, based on Bernstein and
Vazirani's parity problem, that retrieve the entire contents of a quantum
database $Y$ in a single query. The class includes binary search problems and
coin-weighing problems. Our methods far exceed the efficiency of classical
algorithms which are bounded by the classical information-theoretic bound. We
show the connection between classical algorithms based on several compression
codes and our quantum-mechanical method.
