  Quantum Metrology calculates the ultimate precision of all estimation
strategies, measuring what is their root mean-square error (RMSE) and their
Fisher information. Here, instead, we ask how many bits of the parameter we can
recover, namely we derive an information-theoretic quantum metrology. In this
setting we redefine "Heisenberg bound" and "standard quantum limit" (the usual
benchmarks in quantum estimation theory), and show that the former can be
attained only by sequential strategies or parallel strategies that employ
entanglement among probes, whereas parallel-separable strategies are limited by
the latter. We highlight the differences between this setting and the
RMSE-based one.
