Here we propose a general protocol for dual-channel lock-in detection of high-frequency ac signals. We find that the effect of a high-frequency target signal can be modulated through the application of rapidly oscillating driving fields. Based on this mechanism, we develop a quantum dual-channel lock-in detection protocol for high-frequency signals, which not only extends the accessible frequency range of quantum sensing but also enables the simultaneous estimation of the signal amplitude and initial phase. Furthermore, we present a feasible implementation scheme of the protocol based on nitrogen-vacancy centers in diamond. Numerical simulations demonstrate that the proposed protocol can effectively filter out background noise and significantly improve the signal-to-noise ratio. Our results provide a promising approach for realizing noise-resistant detection of weak signals in the high-frequency regime.
Here we propose a general protocol for dual-channel lock-in detection of high-frequency ac signals. We find that the effect of a high-frequency target signal can be modulated through the application of rapidly oscillating driving fields. Based on this mechanism, we develop a quantum dual-channel lock-in detection protocol for high-frequency signals, which not only extends the accessible frequency range of quantum sensing but also enables the simultaneous estimation of the signal amplitude and initial phase. Furthermore, we present a feasible implementation scheme of the protocol based on nitrogen-vacancy centers in diamond. Numerical simulations demonstrate that the proposed protocol can effectively filter out background noise and significantly improve the signal-to-noise ratio. Our results provide a promising approach for realizing noise-resistant detection of weak signals in the high-frequency regime.
In recent years, quantum lock-in detection has emerged as a promising technique to accurately detect weak signals submerged in background noise. However, the signal-to-noise ratio of existing protocols is severely limited by spectral leakage resulting from control operations implemented in pulse form. Here, we propose a general protocol for realizing quantum lock-in detection by employing successive quantum adiabatic evolution. In our protocol, the signal modulation is achieved by adiabatically controlling the time evolution of the quantum probe, which enables the implementation of sinusoidal modulation functions. The realization of sinusoidal-wave modulation substantially mitigates the problem of spectral leakage and facilitates the extraction of the complete characteristics of the target signals. We present a practical implementation scheme of adiabatic quantum lock-in detection based on nitrogen-vacancy centers in diamond, and demonstrate that the proposed protocol possesses strong resilience against experimental imperfections. Our results establish adiabatic quantum lock-in detection as a robust and experimentally accessible approach to detection of weak alternating signals in noisy environments, thus promoting the advance of real-world quantum sensing technologies.
In recent years, the field of quantum sensing has garnered increasing attention due to its potential to revolutionize various scientific and technological domains. Among the different quantum sensors, the nitrogen-vacancy (NV) color center in diamond stands out for its ease of use, ability to be read out and initialized with a laser, and long coherence times even at room temperature. Over the past years, numerous quantum control sequences have been developed to successfully deploy NV sensors in diverse situations, such as measuring nearby spin clusters, classical AC signals, and static magnetic fields. However, the NV center faces limitations when coupling to high frequency signals. More specifically, as the frequency of the target signal increases, stronger driving fields over NVs are needed, ultimately reaching the limits of current experimental capabilities. In this thesis, we propose several protocols to address this high-frequency problem in different scenarios.
Nitrogen-vacancy color centers can perform highly sensitive and spatially resolved quantum measurements of physical quantities such as magnetic field, temperature, and pressure.Meanwhile, sensing so many variables at the same time often introduces additional noise, causing a reduced accuracy.Here, a dual-microwave time-division multiplexing protocol is used in conjunction with a lock-in amplifier in order to decouple temperature from the magnetic field and vice versa.In this protocol, dual-frequency driving and frequency modulation are used to measure the magnetic and temperature field simultaneously in real time.The sensitivity of our system is about 3.4 nT= Hz p and 1.3 mK= Hz p , respectively.Our detection protocol not only enables multifunctional quantum sensing, but also extends more practical applications.
In recent years, the nitrogen-vacancy (NV) center in diamonds has been demonstrated to be a high-performance multiphysics sensor, where a lock-in amplifier (LIA) is often adopted to monitor photoluminescence changes around the resonance. It is rather complex when multiple resonant points are utilized to realize a vector or temperature-magnetic joint sensing. In this article, we present a novel scheme to realize multipoint lock-in detection with only a single-channel device. This method is based on a direct digital synthesizer (DDS) and frequency-shift keying (FSK) technique, which is capable of freely hopping frequencies with a maximum of 1.4 GHz bandwidth and encoding an unlimited number of resonant points during the sensing process. We demonstrate this method in experiments and show it would be generally useful in quantum multi-frequency excitation applications, especially in the portable and highly mobile cases.
High-precision measurement of oscillating signal is a ubiquitous issue in fundamental science and a critical task in practical technologies. In quantum metrology, quantum lock-in detection provide an efficient method for measuring such signal. In general, when the initial phase of the oscillating signal is unknown,quantum double lock-in detection can effectively extract complete information about the signal's amplitude, frequency, and initial phase. Conventional quantum double lock-in detection requires two individual quantum interferometry, each of which must undergo state preparation and readout. However, the time for state preparation and readout need not be negligible in practical experiments. In particular, the time for state preparation is longer than the time for sensing. To save experimental resources, it is challenging to achieve quantum double lock-in detection just via a single quantum interferometry while still extracting complete information about the signal's amplitude, frequency, and initial phase. Here, we present a general protocol for achieving a quantum double lock-in detection just via a single quantum interferometry under a sequential orthogonal periodic multipulse sequences. In particular, if the input state is a Greenberger-Horne-Zeilinger state and two interaction-based operations are applied during interferometry, the measurement precisions for frequency, amplitude, and initial phase can both approach the Heisenberg limit. Our study paves a new way for measuring oscillating signals with a single quantum interferometry, and provides a feasible method for achieving Heisenberg-limited detection of alternating signals.
One of the promising solid-state quantum sensors is nitrogen-vacancy (NV) centers in diamond which can maintain quantum state at room temperature and under atmospheric pressure condition. Further improvement of sensitivity of the sensor is needed to detect the magnetic field from the brain. Noise reduction and simplified system are key techniques especially for the practical use of highly sensitive DC magnetic sensor. In this study, we devised a digital filtering detection method without synchronization between detector and modulator which is a similar noise reduction effect as a lock-in detection technique. We implemented the detection method for the quantum diamond sensor system with the large sensor volume [1]. The Lock-in detection technique is a typical high sensitivity technique for DC magnetic measurement. There are several different implementations of lock-in detection technique for the quantum diamond sensor including microwave modulation, magnetic field modulation, and laser modulation. However, it is a challenging task to obtain high magnetic sensitivity with a compact sensor module because these lock-in detection techniques require a lock-in amplifier or synchronization system. We devised a digital filtering detection method which is an alternative method to the lock-in detection technique. Fluorescence from the NV center is modulated by frequency modulated microwave during optical detected magnetic resonance (ODMR) measurement. The fluorescence is analyzed by digital signal processing which achieves a similar noise reduction effect as a lock-in detection technique. Our method relies on a fact that ODMR converts frequency modulation to amplitude modulation. Thus, our method is applicable not only to the NV center system but also another color center system. This work was supported by MEXT Q-LEAP, CAO PRISM, Japan. [1] Y. Masuyama et al., Rev. Sci. Instrum. 89, 125007 (2018).