Distributed Quantum Fiber Magnetometry

Abstract

Nitrogen-vacancy (NV) quantum magnetometers offer exceptional sensitivity and long-term stability. However, their use to date in distributed sensing applications, including remote detection of ferrous metals, geophysics, and biosensing, is limited due to the need to combine optical, microwave (MW), and magnetic excitations into a single system. Existing approaches have yielded localized devices but not distributed capabilities. In this study, a continuous system-in-a-fiber architecture is reported, which enables distributed magnetic sensing over extended lengths. Key to this realization is a thermally drawn fiber that has hundreds of embedded photodiodes connected in parallel and a hollow optical waveguide that contains a fluid with NV diamonds. This fiber is placed in a larger coaxial cable to deliver the required MW excitation. This distributed quantum sensor is realized in a water-immersible 90-m-long cable with 102 detection sites. A sensitivity of 63 ± 5 nT Hz −1/2 per site, limited by laser shot noise, is established along a 90 m test section. This fiber architecture opens new possibilities as a robust and scalable platform for distributed quantum sensing technologies.Current distributed fiber sensors have high sensitivity to temperature, [1,2] strain, [3][4][5] and pressure, [6][7][8] but not to magnetic fields. [9][10][11] Here, we add distributed spin-based quantum magnetometry to the sensing capabilities of distributed fiber sensors through the integration of NV ensembles. Recent years have seen the rapid advancement of NV solid-state quantum sensors because of their excellent sensitivity to magnetic fields, [12][13][14][15] with sub-nT Hz −1/2 sensitivity in the dc limit, [16,17] high dynamic range vector resolution, [18,19] and remarkable long-term stability. [20,21] Recent advances toward component integration have achieved magnetometry point probes consisting of micro-diamonds on fiber facets [22] or nanodiamonds on tapered fibers. [23] However, practical devices will require compact and stable architectures

Integrated and Portable Magnetometer Based on Nitrogen‐Vacancy Ensembles in Diamond

“…The NV centers are susceptible to magnetic fields through the Zeeman effect yielding a magnetic field dependent electron spin resonance for the spin transitions from the to the ground states, see Figure 1b. Zeeman splitting leads to a shift of the resonance frequencies of the spin transitions of NV centers as [ 23 ] where GHz is the zero‐field splitting due to the spin–spin interaction at room temperature, GHz T −1 the gyromagnetic ratio with μ B the Bohr magneton, the approximately isotropic g ‐factor, h the Planck constant, and B 0 the projection of the magnetic field on the corresponding NV axis. [ 24 ] Due to the Zeeman effect, the shift of the resonance frequencies from D gs is proportional to the magnetic field.…”

“…Based on different approaches, recent works have focused on the development of prototypes that can enable the NV centers for industrial product applications. [18][19][20][21][22][23] Here, we demonstrate a fiber-integrated magnetometer based on NV centers in diamond. The compact design of the magnetic field sensor was achieved by using a single-mode fiber for the optical initialization of the NV centers and deploying a balanced detection scheme built up by two photodiodes positioned close to the diamond.…”

“…Based on different approaches, recent works have focused on the development of prototypes that can enable the NV centers for industrial product applications. [ 18–23 ]…”

Quantum nanophotonic and nanoplasmonic sensing: towards quantum optical bioscience laboratories on chip

“…, with the potential to be improved even further. Another exciting design for NV-based magnetometry is the distributed quantum fibre magnetometer, which allows for distributed magnetic sensing capabilities over extended lengths with a sensitivity of 63 ± 5 nT/ ̅̅ ̅ Hz √ per site [276].…”

Ultrasensitive Magnetic Field Sensors for Biomedical Applications

“…Though these magnetometers commonly have a nT/ √ Hz [194,195] or pT/ √ Hz [196] limit of detection, they have a number of noteworthy applications due to the fact of their special features. For example, in Reference [197] the authors demonstrate distributed magnetic field sensing using a thermally drawn fiber with embedded photodiodes and a hollow waveguide containing fluid with diamond material having nitrogen-vacancy (NV) defects. This magnetometry method relies on the scanning of NV's in an oil droplet through a hollow-core fiber.…”