In this work, we theoretically proposed and experimentally demonstrated the enhanced effect of prior curvature precondition on temperature sensing in a quantum-enhanced sensing system, which is constructed by combining an all-fiber two-mode squeezed light source and a Sagnac loop. By choosing the prior optimum length and curvature of polarization-maintaining fiber inside the Sagnac loop, both signal-to-noise ratio (SNR) and sensitivity can be effectively enhanced. The experimental results are summarized as follows. SNR is enhanced by the factor of 0.38 dB under balanced measurement condition. Under unbalanced measurement condition, the enhanced factors with regard to sensing depth are 0.22 and 2.34 dB for the classical double-channel light source and two-mode squeezed light source, respectively. With the support of curvature precondition, the sensing depth of the former one 15.62 dB is enhanced to 31.49 dB of the latter one by an enhanced factor of 15.87 dB, which is larger than 13.75 dB in the absence of curvature precondition, this enhanced effect still exists in the temperature sensitivity (0.982 dB/°C <1.134 dB/°C) and SNR (0.54 dB <1.7 dB). These results confirm the potential prospects of using the cross effects from other physical quantities to enhance temperature sensing in a quantum-enhanced sensing system.
We propose a quantum sensing protocol that leverages the dynamical response of physical observables to quenches in quantum systems. Specifically, we use the nitrogen-vacancy (NV) color center in diamond to realize both scalar and vector magnetometry via quantum response. Furthermore, we suggest a method for detecting the instantaneous motion of magnetic nanoparticles. To achieve this, we derive the closed exact form of the Berry curvature corresponding to NV centers and design quenching protocols to extract the Berry curvature via dynamical response. By constructing and solving nonlinear equations, the magnetic field and instantaneous motion velocity of the magnetic nanoparticle can be deduced. We investigate the feasibility of our sensing scheme in the presence of decoherence and show through numerical simulations that it is robust to decoherence. Intriguingly, we have observed that a vanishing nuclear spin polarization in diamond benefits our dynamic sensing scheme, which stands in contrast with conventional Ramsey-based schemes. In comparison with Ramsey-based sensing schemes, our proposed scheme can sense an arbitrary time-dependent magnetic field if its time dependence is nearly adiabatic.
Achieving joint quantum-enhanced precision in multiparameter sensing requires both high sensitivity and measurement compatibility. These two aspects are characterized by the quantum Fisher information matrix (QFIM) and the Uhlmann curvature matrix (UCM), respectively, with weak compatibility corresponding to the vanishing of the relevant UCM elements. Here, we develop a symmetry-projection framework that classifies phase generators into subspace-preserving and subspace-changing sectors. For probe states confined to a symmetry subspace, symmetry projection imposes a common block-diagonal structure on the QFIM and UCM, rendering cross-sector parameters simultaneously free from information cross-talk and measurement incompatibility. When the subspace-changing generators act as scalars within the occupied subspace, the corresponding QFIM block reduces to four times the symmetrized covariance matrix, even for mixed probe states. For parity-protected collective
SU(2) systems, this structure singles out the transverse anti-squeezed quadrature and the longitudinal mean-spin direction as natural optimal sensing axes. Applied to a dissipative one-axis twisting model, the dynamically generated probe state exhibits identically vanishing UCM elements for transverse--longitudinal parameter pairs, while maintaining nearly balanced, Heisenberg-scaled QFIM components over a broad transient window. Our work opens a route to symmetry-protected, weakly compatible multiparameter sensing in interacting quantum many-body systems.