Single-spin entanglement

Hideaki Hakoshima, Yuichiro Matsuzaki

Single spin detection is one of the important tasks in the field of quantum metrology.Many experiments about the single spin detection has been performed.However, due to the weak magnetic fields from the single spin, a long measurement time is required to achieve a reasonably high signalto-noise ratio.Here, we propose an alternative way to realize rapid and accurate single spin detection with entangled states.While it is known that entanglement can improve the sensitivity to measure globally applied magnetic fields, we investigate a strategy to use the entanglement for detecting spatially inhomogeneous magnetic fields from the target single spin.We show that the entanglement significantly increases the signal to noise ratio for the single spin detection even under the effect of realistic noise.Our results pave the way for practical single spin detection.

K. Sengupta

Hideaki Hakoshima, Yuichiro Matsuzaki

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.

Guo‐Feng Zhang, Shu‐Shen Li

Hideo Kosaka, Naeko Niikura

Quantum entanglement, a key resource for quantum information science, is inherent in a solid. It has been recently shown that entanglement between a single optical photon and a single spin qubit in a solid is generated via spontaneous emission. However, entanglement generation by measurement is rather essential for quantum operations. We here show that the physics behind the entangled emission can be time reversed to demonstrate entangled absorption mediated by an inherent spin-orbit entanglement in a single nitrogen vacancy center in diamond. Optical arbitrary spin state preparation and complete spin state tomography reveal the fidelity of the entangled absorption to be 95%. With the entangled emission and absorption of a photon, materials can be spontaneously entangled or swap their quantum state based on the quantum teleportation scheme.