Generalized limits for single-parameter quantum estimation.
We develop generalized bounds for quantum single-parameter estimation problems for which the coupling to the parameter is described by intrinsic multisystem interactions. For a Hamiltonian with k-system parameter-sensitive terms, the quantum limit scales as 1/Nk, where N is the number of systems. These quantum limits remain valid when the Hamiltonian is augmented by any parameter-independent interaction among the systems and when adaptive measurements via parameter-independent coupling to ancillas are allowed.
Boixo
Sergio
S
Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131, USA.
Flammia
Steven T
ST
Caves
Carlton M
CM
Geremia
J M
JM