title: Quantum-enhanced multiparameter estimation in multiarm interferometers.
abstract: Quantum metrology is the state-of-the-art measurement technology. It uses quantum resources to enhance the sensitivity of phase estimation over that achievable by classical physics. While single parameter estimation theory has been widely investigated, much less is known about the simultaneous estimation of multiple phases, which finds key applications in imaging and sensing. In this manuscript we provide conditions of useful particle (qudit) entanglement for multiphase estimation and adapt them to multiarm Mach-Zehnder interferometry. We theoretically discuss benchmark multimode Fock states containing useful qudit entanglement and overcoming the sensitivity of separable qudit states in three and four arm Mach-Zehnder-like interferometers - currently within the reach of integrated photonics technology.
authors.affiliation: Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Roma, Italy.
authors.forename: Mario A
authors.initials: MA
authors.lastname: Ciampini
authors.affiliation: Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Roma, Italy.
authors.forename: Nicolò
authors.initials: N
authors.lastname: Spagnolo
authors.affiliation: Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Roma, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Vitelli
authors.affiliation: QSTAR, INO-CNR and LENS, Largo Enrico Fermi 2, I-50125 Firenze, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Pezzè
authors.affiliation: QSTAR, INO-CNR and LENS, Largo Enrico Fermi 2, I-50125 Firenze, Italy.
authors.forename: Augusto
authors.initials: A
authors.lastname: Smerzi
authors.affiliation: Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Roma, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Sciarrino