【报告题目】From local thermometry to general quantum multi-parameter global sensing
【报告人】Victor Montenegro 博士, 电子科技大学
【报告摘要】Measuring the effective temperature of the oscillator is perhaps one of the most relevant steps in the characterization of quantum optomechanical systems. Conventionally, the cavity is strongly driven, and the overall system is well-described by a Gaussian preserving Hamiltonian. Here, we consider an undriven optomechanical system via non-Gaussian radiation-pressure interaction. We show that the optical probe gets a nonlinear phase, resulting from the non-Gaussian interaction, and undergoes an incoherent phase diffusion process. We propose using a nonlinear Kerr medium before a homodyne detector that enhances the precision to nearly saturate the ultimate quantum bound given by the quantum Fisher information . The above sensing procedure falls into local sensing, namely when the quantum sensor operates efficiently only when the unknown parameters vary within a very narrow region. In the second part of this talk, we present a systematic method for optimizing the sensor to operate with its best precision over any arbitrarily large interval, namely, global sensing. By exploiting quantum many-body probes, our protocol harnesses the criticality for significantly enhancing the precision of multi-parameter estimation, independent of the sensing intervals .
 V. Montenegro, M. G. Genoni, A. Bayat, and M. G. A. Paris, "Mechanical oscillator thermometry in the nonlinear optomechanical regime". Phys. Rev. Research 2, 043338 (2020).
 V. Montenegro, U. Mishra, and A. Bayat, "Global sensing and its impact for quantum many-body probes with criticality," arXiv:2102.03843 (2021) [to appear in Phys. Rev. Lett.]