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 ``standar 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.
This is joint work with Majid Hassani and with Chiara Macchiavello. It has been published in the paper:
M. Hassani, C. Macchiavello, L. Maccone,``Digital quantum metrology'', Phys. Rev. Lett. 119, 200502 (2017).
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