Vector-magnetic-field sensing via multifrequency control of nitrogen-vacancy centers in diamond

Abstract

An ensemble of nitrogen-vacancy (NV) centers in diamond is an attractive device to detect small magnetic fields. In particular, by exploiting the fact that the NV center can be aligned along one of four different axes due to C3ν symmetry, it is possible to extract information concerning vector magnetic fields. However, in the conventional scheme, low readout contrasts of the NV centers significantly decrease the sensitivity of the vector magnetic field sensing. Here, we propose a way to improve the sensitivity of the vector magnetic field sensing of the NV centers using multi-frequency control. Since the Zeeman energy of the NV centers depends on the direction of the axis, we can independently control the four types of NV centers using microwave pulses with different frequencies. This allows us to use every NV center for the vector field detection in parallel, which effectively increases the readout contrast. Our results pave the way to realize a practical diamond-based vector field sensor.The detection of small magnetic fields is important in the field of metrology, because there are many potential applications in biology and medical science. The performance of a magnetic field sensor is characterized by its spatial resolution and sensitivity; therefore, a significant amount of effort has been devoted to creating a device that can measure small magnetic fields in a local region [1][2][3].Nitrogen vacancy (NV) centers in diamond are fascinating candidates with which to construct a magnetic field sensor [4][5][6][7]. The NV center is a spin 1 system, and the frequency of the | ± 1 states can be shifted by magnetic fields. We can use this system as an effective two-level system spanned by |0 and |1 with a frequency selectivity where | − 1 is significantly detuned. We can implement gate operations of the spins in NV centers using microwave pulses [8][9][10][11]. It is possible to detect DC (AC) magnetic fields by implementing a Ramsey interference (spin echo) measurement [4][5][6]. Moreover, NV centers have a long coherence time, e.g., a few milli-seconds at a room temperature and a second at low temperature [12][13][14]. In addition, because the NV centers can be strongly coupled with optical photons, we can read out the state of the NV centers via fluorescence from the optical transitions [9,10]. The NV centers can be embedded in nanocrystals, which allows the NV centers to interact with local magnetic fields [15]. These properties are prerequisite to realizing a high-performance sensor for magnetic fields.Recently, vector magnetic field sensing by NV centers has become an active area of interest [16][17][18][19][20][21]. The NV center is aligned along one of four different axes due to C 3ν symmetry. The Zeeman energies of the NV centers are determined by gµ b B · d j (j = 1, 2, 3, 4) where g denotes the g factor, µ b denotes a Bohr magneton, B denotes the magnetic fields, and d j denotes the direction of the j-th NV axis. By sequentially performing Ramsey interference or spin echo measurements on NV centers with...

Magnetic resonance in defect spins mediated by spin waves

“…Hence, the resonance experiment can be used to sense a probe magnetic field resolving its direction on the one hand and to measure the crystal structure of a nanodiamond indirectly on the other hand. 15,16…”

Preparing Dicke states in a spin ensemble using phase estimation

“…Sensing using an ensemble of NV centers, without preparing them in a particular entangled state, has been used at ambient temperatures in, e.g., Refs. [37,38].…”

“…There are four types of NV centers, each aligned with a different NV axis of the carbon lattice (i.e., the direction from the vacancy to the nitrogen) [38], and one does not control the orientation of these NV axes. We choose one type of NV center and call its NV axis the z axis so that its associated electronic spin (S = 1) has Hamiltonian [50]…”

“…The four types of NV centers are simultaneously coupled to the flux qubit, each having a different coupling strength as their NV axes are different and having a different resonance frequency [38]. In principle all types of NV centers could be used for sensing different components of the magnetic field [37].…”

Coherent remote control of quantum emitters embedded in polymer waveguides

“…A possible limitation for application of NV centers as magnetometers is the need for direct optical access to the NV centers under investigation, when probing, for instance, strongly scattering, opaque media, or sample being sensitive to the excitation or fluorescence light. We show that our waveguides mediate this access to individual integrated nanodiamonds for excitation light and read out, such that these nanodiamonds can be used for vector magnetometry, according to 31 . Another possibility to extract the magnetic field components in a Cartesian basis is to modulate magnetic offset fields in the respective directions with incommensurable frequencies, see 32 .…”