Exponentially Enhanced Quantum Metrology
Shasanka Mohan Roy, Samuel L. Braunstein · Physical Review Letters · 2008
We show that when a suitable entanglement-generating unitary operator depending on a parameter is applied on N qubits in parallel, a precision of the order of 2(-N) in estimating the parameter may be achieved. This exponentially improves the precision achievable in classical and in quantum nonentangling strategies.