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Heterodyne sensing of microwaves with a quantum sensor

Jonas Meinel, Vadim Vorobyov, Boris V. Yavkin, Durga Bhaktavatsala Rao Dasari, Hitoshi Sumiya, Shinobu Onoda, Junichi Isoya, Jörg Wrachtrup, Onoda Shinobu

Published May 1, 2021• 61 citations
OpenAlex

Abstract

Abstract Diamond quantum sensors are sensitive to weak microwave magnetic fields resonant to the spin transitions. However, the spectral resolution in such protocols is ultimately limited by the sensor lifetime. Here, we demonstrate a heterodyne detection method for microwaves (MW) leading to a lifetime independent spectral resolution in the GHz range. We reference the MW signal to a local oscillator by generating the initial superposition state from a coherent source. Experimentally, we achieve a spectral resolution below 1 Hz for a 4 GHz signal far below the sensor lifetime limit of kilohertz. Furthermore, we show control over the interaction of the MW-field with the two-level system by applying dressing fields, pulsed Mollow absorption and Floquet dynamics under strong longitudinal radio frequency drive. While pulsed Mollow absorption leads to improved sensitivity, the Floquet dynamics allow robust control, independent from the system’s resonance frequency. Our work is important for future studies in sensing weak microwave signals in a wide frequency range with high spectral resolution.

Related papers

Heterodyne sensing of microwaves with a quantum sensor

Jonas Meinel, Vadim Vorobyov, Boris V. Yavkin +5 more

Diamond quantum sensors are sensitive to weak microwave magnetic fields resonant to the spin transitions. However, the spectral resolution in such protocols is ultimately limited by the sensor lifetime. Here, we demonstrate a heterodyne detection method for microwaves (MW) leading to a lifetime independent spectral resolution in the GHz range. We reference the MW signal to a local oscillator by generating the initial superposition state from a coherent source. Experimentally, we achieve a spectral resolution below 1 Hz for a 4 GHz signal far below the sensor lifetime limit of kilohertz. Furthermore, we show control over the interaction of the MW-field with the two-level system by applying dressing fields, pulsed Mollow absorption and Floquet dynamics under strong longitudinal radio frequency drive. While pulsed Mollow absorption leads to improved sensitivity, the Floquet dynamics allow robust control, independent from the system's resonance frequency. Our work is important for future studies in sensing weak microwave signals in a wide frequency range with high spectral resolution.

arXiv:2008.10068•Nature Communications•May 12, 2021•82 citations

Quantum sensing of weak radio-frequency signals by pulsed Mollow absorption spectroscopy

Timo Joas, A. M. Waeber, Georg Braunbeck +1 more

Abstract Quantum sensors—qubits sensitive to external fields—have become powerful detectors for various small acoustic and electromagnetic fields. A major key to their success have been dynamical decoupling protocols which enhance sensitivity to weak oscillating (AC) signals. Currently, those methods are limited to signal frequencies below a few MHz. Here we harness a quantum-optical effect, the Mollow triplet splitting of a strongly driven two-level system, to overcome this limitation. We microscopically understand this effect as a pulsed dynamical decoupling protocol and find that it enables sensitive detection of fields close to the driven transition. Employing a nitrogen-vacancy center, we detect GHz microwave fields with a signal strength (Rabi frequency) below the current detection limit, which is set by the center’s spectral linewidth $$1{\rm{/}}T_2^*$$ 1 ∕ T 2 * . Pushing detection sensitivity to the much lower 1/ T 2 limit, this scheme could enable various applications, most prominently coherent coupling to single phonons and microwave photons.

arXiv:1702.06710•Nature Communications•Oct 11, 2017•68 citations

Floquet Diamond Sensor with Optimal Precision

Qigeng Duan, Teng Li, Siqi Chen +2 more

The diamond sensor has emerged as a promising platform for quantum sensing, enabling the estimation of physical quantities -- such as microwave~(MW) field -- with precision unattainable by classical counterpart. However, traditional diamond sensors suffer severe precision degradation when the signal MW is not resonant with the sensor transition frequency. Here, we propose and demonstrate a Floquet diamond sensor~(FDS) for high-precision off-resonant MW amplitude sensing without attenuating the strength of the signal MW. The periodic driven field effectively induces an quasi-energy shift that matches the off-resonant MW frequency. The measurement precision of FDS is characterized by quantum Fisher information, which approaches the ultimate precision -- Heisenberg limit -- within the coherent time. Furthermore, the FDS exhibits robust tolerance to practical control errors and is compatible with dynamical coupling protocol, enabling a robust and high-sensitivity magnetic sensing. Our results confirm the quantum advantage of quantum sensing and provide a practical technology for high-precision off-resonant MW sensing.

arXiv:2510.03618•Oct 4, 2025•0 citations

High-resolution, Wide-frequency-range Magnetic Spectroscopy with Solid-state Spin Ensembles

Ronald Lee Walsworth, Zechuan Yin, Justin J. Welter +2 more

Abstract Quantum systems composed of solid-state electronic spins can be sensitive detectors of narrowband magnetic fields. A prominent example is the nitrogen-vacancy (NV) center in diamond, which has been employed for magnetic spectroscopy with high spatial and spectral resolution. However, NV-diamond spectroscopy protocols are typically based on dynamical decoupling sequences, which are limited to low-frequency signals (≲ 20 MHz) due to the technical requirements on microwave (MW) pulses used to manipulate NV electronic spins. In this work, we experimentally demonstrate a high-resolution magnetic spectroscopy protocol that integrates a quantum frequency mixing (QFM) effect in a dense NV ensemble with coherently averaged synchronized readout (CASR) to provide both a wide range of signal frequency detection and sub-Hz spectral resolution. We assess the sensitivity of this QFM-CASR protocol across a frequency range of 10 MHz to 4 GHz. By measuring the spectra of multi-frequency signals near 0.6, 2.4 and 4 GHz, we demonstrate sub-Hz spectral resolution with a nT-scale noise floor for the target signal, and precise phase measurement with error <1°. Compared to state-of-the-art NV-diamond techniques for narrowband magnetic spectroscopy, the QFM-CASR protocol greatly extends the detectable frequency range, enabling applications in high-frequency radio frequency (RF) and MW signal microscopy and analysis, as well as tesla-scale nuclear magnetic resonance (NMR) spectroscopy of small samples.

•Jan 24, 2025•0 citations

High bandwidth heterodyne sensing with bulk NV diamond

H. A. M. Taylor, J. P. Duff, L. B. Miller +4 more

Developing high performance portable sensors is of significant importance for both terrestrial and satellite communications, with quantum sensors offering potential advantages in sensitivity and bandwidth. The nitrogen vacancy center in diamond is a popular quantum sensing platform for its relative simplicity and wide range of acceptable operating conditions, but suffers a limited instantaneous bandwidth due to the narrow linewidth of the spin resonance. In this work, we first present a magnetic quantum sensing scheme utilizing heterodyne mixing with strong optical and microwave driving, achieving MHz-scale instantaneous bandwidth with a sensitivity of $548 \; \text{pT/}\sqrt{\text{Hz}}$ in an active diamond volume of $ 2.5\times 10^{-4} \; \text{mm}^3$ with $2 \times 10^{11}$ NV centers. We then demonstrate expansion of the sensing bandwidth by employing a strong magnetic gradient and many individually modulated microwave control fields, expanding the single resonance bandwidth to 48 MHz with a peak sensitivity of $8.5 \; \text{nT/}\sqrt{\text{Hz}}$.

quant-pharXiv:2610.39022•Oct 30, 2026•0 citations

Extending radiowave frequency detection range with dressed states of solid-state spin ensembles

Jens C. Hermann, Roberto Rizzato, Fleming Bruckmaier +3 more

Quantum sensors using solid-state spin defects excel in the detection of radiofrequency (RF) fields, serving various applications in communication, ranging, and sensing. For this purpose, pulsed dynamical decoupling (PDD) protocols are typically applied, which enhance sensitivity to RF signals. However, these methods are limited to frequencies of a few megahertz, which poses a challenge for sensing higher frequencies. We introduce an alternative approach based on a continuous dynamical decoupling (CDD) scheme involving dressed states of nitrogen vacancy (NV) ensemble spins driven within a microwave resonator. We compare the CDD methods to established PDD protocols and demonstrate the detection of RF signals up to ~85 MHz, about ten times the current limit imposed by the PDD approach under identical conditions. Implementing the CDD method in a heterodyne/synchronized protocol combines the high-frequency detection with high spectral resolution. This advancement extends to various domains requiring detection in the high frequency (HF) and very high frequency (VHF) ranges of the RF spectrum, including spin sensor-based magnetic resonance spectroscopy at high magnetic fields.

arXiv:2407.14483•npj Quantum Information•Oct 26, 2024•13 citations
Abstract Diamond quantum sensors are sensitive to weak microwave magnetic fields resonant to the spin transitions. However, the spectral resolution in such protocols is ultimately limited by the sensor lifetime. Here, we demonstrate a heterodyne detection method for microwaves (MW) leading to a lifetime independent spectral resolution in the GHz range. We reference the MW signal to a local oscillator by generating the initial superposition state from a coherent source. Experimentally, we achieve a spectral resolution below 1 Hz for a 4 GHz signal far below the sensor lifetime limit of kilohertz. Furthermore, we show control over the interaction of the MW-field with the two-level system by applying dressing fields, pulsed Mollow absorption and Floquet dynamics under strong longitudinal radio frequency drive. While pulsed Mollow absorption leads to improved sensitivity, the Floquet dynamics allow robust control, independent from the system’s resonance frequency. Our work is important for future studies in sensing weak microwave signals in a wide frequency range with high spectral resolution.
Diamond quantum sensors are sensitive to weak microwave magnetic fields resonant to the spin transitions. However, the spectral resolution in such protocols is ultimately limited by the sensor lifetime. Here, we demonstrate a heterodyne detection method for microwaves (MW) leading to a lifetime independent spectral resolution in the GHz range. We reference the MW signal to a local oscillator by generating the initial superposition state from a coherent source. Experimentally, we achieve a spectral resolution below 1 Hz for a 4 GHz signal far below the sensor lifetime limit of kilohertz. Furthermore, we show control over the interaction of the MW-field with the two-level system by applying dressing fields, pulsed Mollow absorption and Floquet dynamics under strong longitudinal radio frequency drive. While pulsed Mollow absorption leads to improved sensitivity, the Floquet dynamics allow robust control, independent from the system's resonance frequency. Our work is important for future studies in sensing weak microwave signals in a wide frequency range with high spectral resolution.
Abstract Quantum sensors—qubits sensitive to external fields—have become powerful detectors for various small acoustic and electromagnetic fields. A major key to their success have been dynamical decoupling protocols which enhance sensitivity to weak oscillating (AC) signals. Currently, those methods are limited to signal frequencies below a few MHz. Here we harness a quantum-optical effect, the Mollow triplet splitting of a strongly driven two-level system, to overcome this limitation. We microscopically understand this effect as a pulsed dynamical decoupling protocol and find that it enables sensitive detection of fields close to the driven transition. Employing a nitrogen-vacancy center, we detect GHz microwave fields with a signal strength (Rabi frequency) below the current detection limit, which is set by the center’s spectral linewidth 1/T2∗1{\rm{/}}T_2^*1/T2∗​ 1 ∕ T 2 * . Pushing detection sensitivity to the much lower 1/ T 2 limit, this scheme could enable various applications, most prominently coherent coupling to single phonons and microwave photons.
The diamond sensor has emerged as a promising platform for quantum sensing, enabling the estimation of physical quantities -- such as microwave~(MW) field -- with precision unattainable by classical counterpart. However, traditional diamond sensors suffer severe precision degradation when the signal MW is not resonant with the sensor transition frequency. Here, we propose and demonstrate a Floquet diamond sensor~(FDS) for high-precision off-resonant MW amplitude sensing without attenuating the strength of the signal MW. The periodic driven field effectively induces an quasi-energy shift that matches the off-resonant MW frequency. The measurement precision of FDS is characterized by quantum Fisher information, which approaches the ultimate precision -- Heisenberg limit -- within the coherent time. Furthermore, the FDS exhibits robust tolerance to practical control errors and is compatible with dynamical coupling protocol, enabling a robust and high-sensitivity magnetic sensing. Our results confirm the quantum advantage of quantum sensing and provide a practical technology for high-precision off-resonant MW sensing.
Abstract Quantum systems composed of solid-state electronic spins can be sensitive detectors of narrowband magnetic fields. A prominent example is the nitrogen-vacancy (NV) center in diamond, which has been employed for magnetic spectroscopy with high spatial and spectral resolution. However, NV-diamond spectroscopy protocols are typically based on dynamical decoupling sequences, which are limited to low-frequency signals (≲ 20 MHz) due to the technical requirements on microwave (MW) pulses used to manipulate NV electronic spins. In this work, we experimentally demonstrate a high-resolution magnetic spectroscopy protocol that integrates a quantum frequency mixing (QFM) effect in a dense NV ensemble with coherently averaged synchronized readout (CASR) to provide both a wide range of signal frequency detection and sub-Hz spectral resolution. We assess the sensitivity of this QFM-CASR protocol across a frequency range of 10 MHz to 4 GHz. By measuring the spectra of multi-frequency signals near 0.6, 2.4 and 4 GHz, we demonstrate sub-Hz spectral resolution with a nT-scale noise floor for the target signal, and precise phase measurement with error <1°. Compared to state-of-the-art NV-diamond techniques for narrowband magnetic spectroscopy, the QFM-CASR protocol greatly extends the detectable frequency range, enabling applications in high-frequency radio frequency (RF) and MW signal microscopy and analysis, as well as tesla-scale nuclear magnetic resonance (NMR) spectroscopy of small samples.
Developing high performance portable sensors is of significant importance for both terrestrial and satellite communications, with quantum sensors offering potential advantages in sensitivity and bandwidth. The nitrogen vacancy center in diamond is a popular quantum sensing platform for its relative simplicity and wide range of acceptable operating conditions, but suffers a limited instantaneous bandwidth due to the narrow linewidth of the spin resonance. In this work, we first present a magnetic quantum sensing scheme utilizing heterodyne mixing with strong optical and microwave driving, achieving MHz-scale instantaneous bandwidth with a sensitivity of 548  pT/Hz548 \; \text{pT/}\sqrt{\text{Hz}}548pT/Hz​ in an active diamond volume of $ 2.5\times 10^{-4} \; \text{mm}^3$ with 2×10112 \times 10^{11}2×1011 NV centers. We then demonstrate expansion of the sensing bandwidth by employing a strong magnetic gradient and many individually modulated microwave control fields, expanding the single resonance bandwidth to 48 MHz with a peak sensitivity of 8.5  nT/Hz8.5 \; \text{nT/}\sqrt{\text{Hz}}8.5nT/Hz​.
Quantum sensors using solid-state spin defects excel in the detection of radiofrequency (RF) fields, serving various applications in communication, ranging, and sensing. For this purpose, pulsed dynamical decoupling (PDD) protocols are typically applied, which enhance sensitivity to RF signals. However, these methods are limited to frequencies of a few megahertz, which poses a challenge for sensing higher frequencies. We introduce an alternative approach based on a continuous dynamical decoupling (CDD) scheme involving dressed states of nitrogen vacancy (NV) ensemble spins driven within a microwave resonator. We compare the CDD methods to established PDD protocols and demonstrate the detection of RF signals up to ~85 MHz, about ten times the current limit imposed by the PDD approach under identical conditions. Implementing the CDD method in a heterodyne/synchronized protocol combines the high-frequency detection with high spectral resolution. This advancement extends to various domains requiring detection in the high frequency (HF) and very high frequency (VHF) ranges of the RF spectrum, including spin sensor-based magnetic resonance spectroscopy at high magnetic fields.