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Ultra-precision single-quadrature quantum magnetometry in cavity electromagnonics

Mehri Sadat Ebrahimi, Ali Motazedifard, Malek Bagheri

Published Nov 11, 2020• 1 citation
OpenAlex

Abstract

A scheme of an ultra-sensitive magnetometer in the cavity quantum electromagnonics where the intracavity microwave mode coupled to a magnonic mode via magnetic dipole interaction is proposed. It is shown that by driving both magnonic and microwave modes with external classical fields and controlling the system parameters, one can reduce the added noise of magnetic field measurement below the standard quantum limit (SQL). Surprisingly, we show that beyond the rotating wave approximation (RWA), not only the added noise can be suppressed, but also the output cavity response to the input signal can be substantially amplified in order to achieve a precise magnetic-field measurement. The sensitivity of the proposed magnetic amplifier-sensor is approximately in the order of $10^{-18}T/\sqrt{Hz}$ which is competitive compared to the current state-of-the-art magnetometers like superconducting quantum interference devices (SQUIDs) and atomic magnetometers. The advantage of the proposed sensor in comparison with the other magnetometers is its high sensitivity at room temperature and sensing in a wide range of frequency up to MHz as well as its capability to signal-response amplification.

Related papers

Single-quadrature quantum magnetometry in cavity electromagnonics

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A scheme of an ultrasensitive magnetometer in the cavity quantum electromagnonics is proposed, where the intracavity microwave mode is coupled to a magnonic mode via magnetic dipole interaction. It is shown that by driving both magnonic and microwave modes with external classical fields and controlling the system parameters, one can reduce the added noise of magnetic field measurement below the standard quantum limit (SQL). Surprisingly, we show that beyond the rotating wave approximation (RWA), not only can the added noise be suppressed but also the output cavity response to the input signal can be substantially amplified in order to achieve a precise magnetic-field measurement. The estimated theoretical sensitivity of the proposed magnetic amplifier-sensor is approximately on the order of ${10}^{\ensuremath{-}18}\phantom{\rule{0.28em}{0ex}}\mathrm{T}/\sqrt{\mathrm{Hz}}$, which is competitive compared to the current state-of-the-art magnetometers like superconducting quantum interference devices (SQUIDs) and atomic magnetometers. The advantages of the proposed sensor in comparison with the other magnetometers is its high sensitivity at room temperature, sensing in a wide range of frequencies up to MHz, and its capability for signal-response amplification.

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Magnonic cavity-enhanced quantum magnetometry with nitrogen-vacancy centre ensembles

Nikhil Kumar

Nitrogen-vacancy (NV) centre ensembles are leading room-temperature magnetometers, but their sensitivity is usually extracted from a single resonance and relies on external microwave and bias-field hardware. This work proposes a chip-scale NV magnetometer built around a one-dimensional YIG/CoFeB magnonic crystal, in which a single structural defect forms a passive magnonic cavity and integrated permanent magnets supply the bias field. Micromagnetic simulations show a defect-localised spin-wave mode at 2.910 GHz inside the 2.5-3.0 GHz magnonic band gap, 40 MHz from the NV zero-field splitting, with a band structure that matches an independent plane-wave calculation. A Tavis-Cummings/Lindblad model in which the microwave reaches the NV ensemble through this mode predicts a hyperfine-resolved optically detected magnetic resonance spectrum that is strong only within the mode linewidth, and a dispersive homodyne response with one steep edge per $^{14}$N hyperfine line. The master-equation solutions agree with the closed-form homodyne steady state ($R^2 > 0.9999$) and with an approximate analytic ODMR theory (peak positions within 0.012 MHz). For a critically coupled readout with room-temperature electronics, combining the three edges gives a projected sensitivity of 93 pT/$\sqrt{\rm Hz}$, a $\sqrt{3}$-fold gain over the best single edge. Mapping the sensitivity against the NV-magnon coupling reveals an optimum near $g_{\rm ens}/2π\approx 0.2$-$0.4$ MHz, where it reaches 72 pT/$\sqrt{\rm Hz}$ for a 0.64 MHz spin linewidth and 19 pT/$\sqrt{\rm Hz}$ for 0.17 MHz, with thermal limits of 6.6 and 1.7 pT/$\sqrt{\rm Hz}$. The antenna-mode coupling, the NV-magnon coupling and the spin linewidth are therefore the main design levers.

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Ultrasensitive Magnetometer using a Single Atom

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Precision sensing, and in particular high precision magnetometry, is a central goal of research into quantum technologies. For magnetometers, often trade-offs exist between sensitivity, spatial resolution, and frequency range. The precision, and thus the sensitivity of magnetometry, scales as 1/sqrt[T_{2}] with the phase coherence time T_{2} of the sensing system playing the role of a key determinant. Adapting a dynamical decoupling scheme that allows for extending T_{2} by orders of magnitude and merging it with a magnetic sensing protocol, we achieve a measurement sensitivity even for high frequency fields close to the standard quantum limit. Using a single atomic ion as a sensor, we experimentally attain a sensitivity of 4.6 pT/sqrt[Hz] for an alternating-current magnetic field near 14 MHz. Based on the principle demonstrated here, this unprecedented sensitivity combined with spatial resolution in the nanometer range and tunability from direct current to the gigahertz range could be used for magnetic imaging in as of yet inaccessible parameter regimes.

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Dispersive magnetometry with a quantum limited SQUID parametric amplifier

Michael Hatridge, Rajamani Vijay, D. H. Slichter +2 more

There is currently fundamental and technological interest in measuring and manipulating nanoscale magnets, particularly in the quantum coherent regime. To observe the dynamics of such systems one requires a magnetometer with not only exceptional sensitivity but also high gain, wide bandwidth, and low backaction. We demonstrate a dispersive magnetometer consisting of a two-junction superconducting quantum interference device (SQUID) in parallel with an integrated, lumped-element capacitor. Input flux signals are encoded as a phase modulation of the microwave drive tone applied to the magnetometer, resulting in a single quadrature voltage signal. For strong drive power, the nonlinearity of the resonator results in quantum limited, phase sensitive parametric amplification of this signal, which improves flux sensitivity at the expense of bandwidth. Depending on the drive parameters, the device performance ranges from an effective flux noise of 0.29 $\ensuremath{\mu}{\ensuremath{\Phi}}_{0}$Hz${}^{\ensuremath{-}1/2}$ and 20 MHz of signal bandwidth to a noise of 0.14 $\ensuremath{\mu}{\ensuremath{\Phi}}_{0}$Hz${}^{\ensuremath{-}1/2}$ and a bandwidth of 0.6 MHz. These results are in excellent agreement with our theoretical model.

arXiv:1003.2466•Physical Review B•Apr 4, 2011•267 citations
A scheme of an ultra-sensitive magnetometer in the cavity quantum electromagnonics where the intracavity microwave mode coupled to a magnonic mode via magnetic dipole interaction is proposed. It is shown that by driving both magnonic and microwave modes with external classical fields and controlling the system parameters, one can reduce the added noise of magnetic field measurement below the standard quantum limit (SQL). Surprisingly, we show that beyond the rotating wave approximation (RWA), not only the added noise can be suppressed, but also the output cavity response to the input signal can be substantially amplified in order to achieve a precise magnetic-field measurement. The sensitivity of the proposed magnetic amplifier-sensor is approximately in the order of 10−18T/Hz10^{-18}T/\sqrt{Hz}10−18T/Hz​ which is competitive compared to the current state-of-the-art magnetometers like superconducting quantum interference devices (SQUIDs) and atomic magnetometers. The advantage of the proposed sensor in comparison with the other magnetometers is its high sensitivity at room temperature and sensing in a wide range of frequency up to MHz as well as its capability to signal-response amplification.
A scheme of an ultrasensitive magnetometer in the cavity quantum electromagnonics is proposed, where the intracavity microwave mode is coupled to a magnonic mode via magnetic dipole interaction. It is shown that by driving both magnonic and microwave modes with external classical fields and controlling the system parameters, one can reduce the added noise of magnetic field measurement below the standard quantum limit (SQL). Surprisingly, we show that beyond the rotating wave approximation (RWA), not only can the added noise be suppressed but also the output cavity response to the input signal can be substantially amplified in order to achieve a precise magnetic-field measurement. The estimated theoretical sensitivity of the proposed magnetic amplifier-sensor is approximately on the order of ${10}^{\ensuremath{-}18}\phantom{\rule{0.28em}{0ex}}\mathrm{T}/\sqrt{\mathrm{Hz}}$, which is competitive compared to the current state-of-the-art magnetometers like superconducting quantum interference devices (SQUIDs) and atomic magnetometers. The advantages of the proposed sensor in comparison with the other magnetometers is its high sensitivity at room temperature, sensing in a wide range of frequencies up to MHz, and its capability for signal-response amplification.
Nitrogen-vacancy (NV) centre ensembles are leading room-temperature magnetometers, but their sensitivity is usually extracted from a single resonance and relies on external microwave and bias-field hardware. This work proposes a chip-scale NV magnetometer built around a one-dimensional YIG/CoFeB magnonic crystal, in which a single structural defect forms a passive magnonic cavity and integrated permanent magnets supply the bias field. Micromagnetic simulations show a defect-localised spin-wave mode at 2.910 GHz inside the 2.5-3.0 GHz magnonic band gap, 40 MHz from the NV zero-field splitting, with a band structure that matches an independent plane-wave calculation. A Tavis-Cummings/Lindblad model in which the microwave reaches the NV ensemble through this mode predicts a hyperfine-resolved optically detected magnetic resonance spectrum that is strong only within the mode linewidth, and a dispersive homodyne response with one steep edge per 14^{14}14N hyperfine line. The master-equation solutions agree with the closed-form homodyne steady state (R2>0.9999R^2 > 0.9999R2>0.9999) and with an approximate analytic ODMR theory (peak positions within 0.012 MHz). For a critically coupled readout with room-temperature electronics, combining the three edges gives a projected sensitivity of 93 pT/Hz\sqrt{\rm Hz}Hz​, a 3\sqrt{3}3​-fold gain over the best single edge. Mapping the sensitivity against the NV-magnon coupling reveals an optimum near gens/2π≈0.2g_{\rm ens}/2π\approx 0.2gens​/2π≈0.2-0.40.40.4 MHz, where it reaches 72 pT/Hz\sqrt{\rm Hz}Hz​ for a 0.64 MHz spin linewidth and 19 pT/Hz\sqrt{\rm Hz}Hz​ for 0.17 MHz, with thermal limits of 6.6 and 1.7 pT/Hz\sqrt{\rm Hz}Hz​. The antenna-mode coupling, the NV-magnon coupling and the spin linewidth are therefore the main design levers.
Precision sensing, and in particular high precision magnetometry, is a central goal of research into quantum technologies. For magnetometers, often trade-offs exist between sensitivity, spatial resolution, and frequency range. The precision, and thus the sensitivity of magnetometry, scales as 1/sqrt[T_{2}] with the phase coherence time T_{2} of the sensing system playing the role of a key determinant. Adapting a dynamical decoupling scheme that allows for extending T_{2} by orders of magnitude and merging it with a magnetic sensing protocol, we achieve a measurement sensitivity even for high frequency fields close to the standard quantum limit. Using a single atomic ion as a sensor, we experimentally attain a sensitivity of 4.6 pT/sqrt[Hz] for an alternating-current magnetic field near 14 MHz. Based on the principle demonstrated here, this unprecedented sensitivity combined with spatial resolution in the nanometer range and tunability from direct current to the gigahertz range could be used for magnetic imaging in as of yet inaccessible parameter regimes.
The crucial limitation of improving the sensitivity of the detection of weak magnetic fields is the unavoidable measurement noise. In this paper, we propose a scheme to achieve precise sensing robust against additional noise by employing a dual frequency bias field modulation within a cavity-magnon system. We find that the antirotating wave term can amplify the signal of the detected magnetic field, but this amplification effect must coexist with the rotating wave term. In particular, by the bias field modulation, we find the robustness against cavity field thermal noise is substantially enhanced, quantum noise and cavity field thermal noise is greatly reduced, and the external magnetic field signal is amplified, thereby improving the weak-magnetic-field sensing system's sensitivity. Compared with the previous scheme, our scheme requires neither an ultrastrong- or deep-strong-coupling mechanism nor the suppression of the additional noise by increasing the electromagnetic cooperativity. Our scheme could provide a valuable candidate for weak-magnetic-field sensing.
Optical atomic magnetometry is a powerful tool for continuous sensing applications, yet, in the absence of quantum correlations, its sensitivity is limited by the standard quantum limit (SQL) stemming from a trade-off between optical probe imprecision and quantum measurement backaction. Beyond-SQL sensitivity requires quantum correlations that modify these measurement noise sources. Here we demonstrate such sensitivity by using entangled state of the probe light and by engineering correlations between measurement imprecision and backaction. Having first explored SQL in a broad range of frequencies, we demonstrate overcoming the limit by combining variational readout with coupling the magnetometer to one mode of a bipartite entangled light state and conditioning the results on the other entangled mode. Tuning the detected light quadratures and combining the signals from the two measurement channels, we achieve sensitivity beyond the SQL in a broad range of acoustic frequencies which has so far remained inaccessible to quantum-noise-limited optical magnetometry.
There is currently fundamental and technological interest in measuring and manipulating nanoscale magnets, particularly in the quantum coherent regime. To observe the dynamics of such systems one requires a magnetometer with not only exceptional sensitivity but also high gain, wide bandwidth, and low backaction. We demonstrate a dispersive magnetometer consisting of a two-junction superconducting quantum interference device (SQUID) in parallel with an integrated, lumped-element capacitor. Input flux signals are encoded as a phase modulation of the microwave drive tone applied to the magnetometer, resulting in a single quadrature voltage signal. For strong drive power, the nonlinearity of the resonator results in quantum limited, phase sensitive parametric amplification of this signal, which improves flux sensitivity at the expense of bandwidth. Depending on the drive parameters, the device performance ranges from an effective flux noise of 0.29 $\ensuremath{\mu}{\ensuremath{\Phi}}_{0}$Hz${}^{\ensuremath{-}1/2}$ and 20 MHz of signal bandwidth to a noise of 0.14 $\ensuremath{\mu}{\ensuremath{\Phi}}_{0}$Hz${}^{\ensuremath{-}1/2}$ and a bandwidth of 0.6 MHz. These results are in excellent agreement with our theoretical model.