Quantum-assisted distortion-free audio signal sensing

Abstract

Quantum sensors are known for their high sensitivity in sensing applications. However, this sensitivity often comes with severe restrictions on other parameters which are also important. Examples are that in measurements of arbitrary signals, limitation in linear dynamic range could introduce distortions in magnitude and phase of the signal. High frequency resolution is another important feature for reconstructing unknown signals. Here, we demonstrate a distortion-free quantum sensing protocol that combines a quantum phase-sensitive detection with heterodyne readout. We present theoretical and experimental investigations using nitrogen-vacancy centers in diamond, showing the capability of reconstructing audio frequency signals with an extended linear dynamic range and high frequency resolution. Melody and speech based signals are used for demonstrating the features. The methods could broaden the horizon for quantum sensors towards applications, e.g. telecommunication in challenging environment, where low-distortion measurements are required at multiple frequency bands within a limited volume.

Optimizing NV magnetometry for Magnetoneurography and Magnetomyography applications

“…Figure 4B further demonstrates the quantum phase signal responses measured in experiments regarding different sequences. Here we use the quantum phase sensitive detection (QPSD) technique described in the reference (Zhang et al, 2022 ), to acquire the quantum phase accumulated through the spin-field interaction. To characterize the frequency responses to different sequences, we apply “dc” fields (low-frequency oscillating fields) and ac fields with an amplitude of 500 nT.…”

“…However, since the MW frequency applied in NV magnetometry significantly changes with B 0 , the dynamic range of an NV sensor is usually limited by instrumentation. Phase-estimation-algorithm (PEA) and QPSD technique can be used to extend the dynamic range of NV sensors based on interferometry schemes (Nusran et al, 2012 ; Zhang et al, 2022 ). Nevertheless, the MW frequency should be near resonant to the NV spins, which leads to a linewidth of a few MHz, corresponding to a dynamic range of roughly 1 Gauss.…”

“…The small sensing volume of NV magnetometers is also expected to be used for gradiometry, which can improve the depth resolution for applications such as MMG. Besides, efforts have been made to enhance the dynamic range of NV magnetometers (Clancy et al, 2021 ; Zhang et al, 2022 ), and the dynamic range of NV magnetometers is much larger than the OPMs. Therefore, NV magnetometers can be more promising for developing an unshielded gradiometry system for bio-magnetic field sensing.…”

Population Oscillations and Ubiquitous Coherences in Multilevel Quantum Systems Driven by Incoherent Radiation

“…In quantum devices, noise is typically a nuisance that disrupts coherent dynamics and must be mitigated to maintain performance in high-precision measurement − and quantum computing. − However, this same noise, in the form of sunlight or heat, can excite highly nontrivial superposition states, − displaying noise-induced coherences that modify fluorescence emission, − enhance the power output of quantum heat engines, , and alter the non-adiabatic relaxation and quantum yield of retinal photoisomerization. − While noise-induced coherences have been studied in many model systems, whether they can arise in any quantum system under the right conditions or if they are only possible in a few special cases remains unclear. In this Letter, we show that noise-induced coherences are generated by incoherent excitation of all but the simplest systems, a consequence of geometric constraints of the light–matter coupling Hamiltonian.…”