Single spin detection with entangled states

Abstract

Single spin detection is an interesting subject in the field of quantum metrology. Many experiments regarding single spin measurements have been performed recently. However, to detect weak magnetic fields from a single spin, it is necessary to take an extremely long measurement time toward realizing a reasonably high signal-To-noise ratio. In this paper, we propose an alternative method to accomplish rapid and accurate detection of a single spin with entangled states. While entanglement is a well-known resource to improve the signal-To-noise ratio when we measure globally applied magnetic fields, we examine a strategy to exploit the entanglement to detect spatially inhomogeneous magnetic fields from a target single spin. We find that entanglement significantly enhances the signal-To-noise ratio for single spin detection, even under the effect of realistic noise. Our results will contribute a great deal to the development of practical single spin detection.