Nitrogen vacancy centers in diamond as angle-squared sensors

TL;DR

This paper demonstrates that nitrogen-vacancy centers in diamond can measure the square of the angle between an external magnetic field and the NV axis with high sensitivity, enabling potential applications in quantum nondemolition measurements.

Contribution

It introduces a novel method to detect the angle squared of magnetic fields relative to NV centers, expanding their sensing capabilities beyond aligned field detection.

Findings

NV centers can measure the square of the magnetic field angle with high sensitivity.

Sensitivity diverges as the external field approaches a specific value.

Potential use as transducers for quantum nondemolition measurements.

Abstract

Nitrogen-vacancy (NV) centers are defects in diamonds, which, due to their electronic structure, have been extensively studied as magnetic field sensors. Such field detection applications usually employ the NV centers to detect field components aligned with the direction of the internally-defined spin axis of the NV center. In this work we detect magnetic fields which are slightly misaligned with the NV center axis. In particular, we demonstrate that the NV center can measure the square of the angle between the magnetic field and the NV center axis with high sensitivity which diverges as the external field approaches a value pre-defined by NV center's internal parameters, in agreement with predictions. These results show that NV centers could be used as sensitive transducers for making quantum nondemolition (QND) measurements on systems such as nanomechanical oscillators.