Magnetic field sensing beyond the standard quantum limit using 10-spin NOON states.

Jones, Jonathan A; Karlen, Steven D; Fitzsimons, Joseph; Ardavan, Arzhang; Benjamin, Simon C; Briggs, G Andrew D; Morton, John J L · Science · 2009

basic_science · Level V

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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.