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Register a new userMiniature cavity-enhanced diamond magnetometer
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Added by
Georgios Chatzidrosos
Publication date
2017
fields
Physics
and research's language is
English
Authors
Georgios Chatzidrosos
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We present a highly sensitive miniaturized cavity-enhanced room-temperature magnetic-field sensor based on nitrogen-vacancy (NV) centers in diamond. The magnetic resonance signal is detected by probing absorption on the 1042,nm spin-singlet transition. To improve the absorptive signal the diamond is placed in an optical resonator. The device has a magnetic-field sensitivity of 28 pT/$sqrt{rm{Hz}}$, a projected photon shot-noise-limited sensitivity of 22 pT/$sqrt{rm{Hz}}$ and an estimated quantum projection-noise-limited sensitivity of 0.43 pT/$sqrt{rm{Hz}}$ with the sensing volume of $sim$ 390 $mu$m $times$ 4500 $mu$m$^{2}$. The presented miniaturized device is the basis for an endoscopic magnetic field sensor for biomedical applications.
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Diamond defect centers are promising solid state magnetometers. Single centers allow for high spatial resolution field imaging but are limited in their magnetic field sensitivity to around 10 nT/Hz^(1/2) at room-temperature. Using defect center ensembles sensitivity can be scaled as N^(1/2) when N is the number of defects. In the present work we use an ensemble of 1e11 defect centers for sensing. By carefully eliminating all noise sources like laser intensity fluctuations, microwave amplitude and phase noise we achieve a photon shot noise limited field sensitivity of 0.9 pT/Hz^(1/2) at room-temperature with an effective sensor volume of 8.5e-4 mm^3. The smallest field we measured with our device is 100 fT. While this denotes the best diamond magnetometer sensitivity so far, further improvements using decoupling sequences and material optimization could lead to fT/Hz^(1/2) sensitivity.
Magnetometers based on nitrogen-vacancy (NV) centers in diamond are promising room-temperature, solid-state sensors. However, their reported sensitivity to magnetic fields at low frequencies (<1 kHz) is presently >10 pT s^{1/2}, precluding potential applications in medical imaging, geoscience, and navigation. Here we show that high-permeability magnetic flux concentrators, which collect magnetic flux from a larger area and concentrate it into the diamond sensor, can be used to improve the sensitivity of diamond magnetometers. By inserting an NV-doped diamond membrane between two ferrite cones in a bowtie configuration, we realize a ~250-fold increase of the magnetic field amplitude within the diamond. We demonstrate a sensitivity of ~0.9 pT s^{1/2} to magnetic fields in the frequency range between 10 and 1000 Hz, using a dual-resonance modulation technique to suppress the effect of thermal shifts of the NV spin levels. This is accomplished using 200 mW of laser power and 20 mW of microwave power. This work introduces a new dimension for diamond quantum sensors by using micro-structured magnetic materials to manipulate magnetic fields.
Quantum emitters are an integral component for a broad range of quantum technologies including quantum communication, quantum repeaters, and linear optical quantum computation. Solid-state color centers are promising candidates for scalable quantum optics due to their long coherence time and small inhomogeneous broadening. However, once excited, color centers often decay through phonon-assisted processes, limiting the efficiency of single photon generation and photon mediated entanglement generation. Herein, we demonstrate strong enhancement of spontaneous emission rate of a single silicon-vacancy center in diamond embedded within a monolithic optical cavity, reaching a regime where the excited state lifetime is dominated by spontaneous emission into the cavity mode. We observe 10-fold lifetime reduction and 42-fold enhancement in emission intensity when the cavity is tuned into resonance with the optical transition of a single silicon-vacancy center, corresponding to 90% of the excited state energy decay occurring through spontaneous emission into the cavity mode. We also demonstrate the largest to date coupling strength ($g/2pi=4.9pm0.3 GHz$) and cooperativity ($C=1.4$) for color-center-based cavity quantum electrodynamics systems, bringing the system closer to the strong coupling regime.
We propose a novel type of composite light-matter magnetometer based on a transversely driven multi-component Bose-Einstein condensate coupled to two distinct electromagnetic modes of a linear cavity. Above the critical pump strength, the change of the population imbalance of the condensate caused by an external magnetic field entails the change of relative photon number of the two cavity modes. Monitoring the cavity output fields thus allows for nondestructive measurement of the magnetic field in real time. We show that the sensitivity of the proposed magnetometer exhibits Heisenberg-like scaling with respect to the atom number. For state-of-the-art experimental parameters, we calculate the lower bound on the sensitivity of such a magnetometer to be of the order of fT/$sqrt{mathrm{Hz}}$--pT/$sqrt{mathrm{Hz}}$ for a condensate of $10^4$ atoms with coherence times of the order of several ms.
We demonstrate operation of a rotation sensor based on the $^{14}$N nuclear spins intrinsic to nitrogen-vacancy (NV) color centers in diamond. The sensor employs optical polarization and readout of the nuclei and a radio-frequency double-quantum pulse protocol that monitors $^{14}$N nuclear spin precession. This measurement protocol suppresses the sensitivity to temperature variations in the $^{14}$N quadrupole splitting, and it does not require microwave pulses resonant with the NV electron spin transitions. The device was tested on a rotation platform and demonstrated a sensitivity of 4.7 $^{circ}/sqrt{rm{s}}$ (13 mHz/$sqrt{rm{Hz}}$), with bias stability of 0.4 $^{circ}$/s (1.1 mHz).
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