A new measurement scheme nears the ultimate precision for quantum sensing

Mankei Tsang of the National University of Singapore proposes a measurement scheme designed to approach the Holevo-Nagaoka bound, a theoretical limit for precision in quantum multiparameter estimation. The work details a physical interaction between multiple quantum objects and bosonic ancillas, followed by measurement of the ancillas, offering a more concrete description of the experimental setup needed to achieve ultimate sensing precision. This approach tackles a challenging second step in a two-step method where collective observables are measured; a recent study described the task as mathematically challenging. The proposal details a scheme that utilizes bosonic ancillas as an intermediary, approximating the collective observables with bosonic quadratures for large numbers of quantum…