title: Magnetic field sensing beyond the standard quantum limit using 10-spin NOON states.
abstract: Quantum entangled states can be very delicate and easily perturbed by their external environment. This sensitivity can be harnessed in measurement technology to create a quantum sensor with a capability of outperforming conventional devices at a fundamental level. We compared the magnetic field sensitivity of a classical (unentangled) system with that of a 10-qubit entangled state, realized by nuclei in a highly symmetric molecule. We observed a 9.4-fold quantum enhancement in the sensitivity to an applied field for the entangled system and show that this spin-based approach can scale favorably as compared with approaches in which qubit loss is prevalent. This result demonstrates a method for practical quantum field sensing technology.
authors.affiliation: Centre for Advanced Electron Spin Resonance (CAESR), Clarendon Laboratory, Oxford University, Oxford OX1 3PU, UK.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Jones
authors.forename: Steven D
authors.initials: SD
authors.lastname: Karlen
authors.forename: Joseph
authors.initials: J
authors.lastname: Fitzsimons
authors.forename: Arzhang
authors.initials: A
authors.lastname: Ardavan
authors.forename: Simon C
authors.initials: SC
authors.lastname: Benjamin
authors.forename: G Andrew D
authors.initials: GA
authors.lastname: Briggs
authors.forename: John J L
authors.initials: JJ
authors.lastname: Morton