Enhancing metrology sensitivity by weak measurements

Andrew N. Jordan, Gerardo I. Viza, Juli 'an Mart 'Inez-Rinc 'on +3 more

Qian Cao, Shang Yu, Liang Xu +1 more

In quantum metrology researching, weak measurement has been widely applied in many aspects, providing weak-value amplification and noise suppressing ability. Recently, several modified schemes of weak measurement have been proposed, such as inverse, almost-balanced, and biased weak measurement. In this study, we enhance a spin-exchange relaxation-free (SERF) magnetometer using the biased weak measurement metrology technique. We establish and simulate a biased weak measurement (BWM)-enhanced SERF magnetometer model. By adjusting the pre-coupling process and analysing the Fisher information, higher sensitivity to magnetic fields is verified in this study. 0.003 fT can be achieved through adjusting pre-coupling process and extinction ratio, which is higher than the best sensitivity of SERF magnetometer in existence. Our work paves the way for embedding weak measurement techniques into atomic magnetometer sensors and greatly improving their sensitivity.

Holger Friedrich Hofmann, Timothy C. Ralph, Ping Koy Lam

Since weak measurements are known to produce measurement values that can be much larger than the maximal eigenvalues of the measured observable, it is an interesting question how this enhancement of the measurement signal relates to the sensitivity of quantum measurements as investigated in the field of quantum metrology. In this presentation, it is pointed out that the estimation of a small interaction parameter using weak measurements actually corresponds to standard quantum metrology, where the logarithmic derivatives of the final measurement probabilities are proportional to the corresponding weak values. The analysis of the general weak measurement formalism then shows that extreme weak values do not improve the sensitivity. Instead, all final measurements with real weak values have the same sensitivity as a final measurement of the eigenvalues. This result supports the view that real weak values can be interpreted as precise, zero uncertainty estimates of a quantum observable, despite their deviation from the eigenvalues of the corresponding operator.

William N. Plick, Nathan Miller

Guangjun Wang, Xue-Ying Duan, Jing-Hui Huang +1 more

Recently, biased quantum weak measurement has shown higher precision than both conventional measurement and standard quantum weak measurement in optical metrology. In this work, a scheme of detecting the ultrasmall rotation velocity in Sagnac's interferometer with biased quantum weak measurement is proposed. In biased quantum weak measurement, additional progress of pre-coupling is introduced in standard quantum weak measurement to enhance the sensitivity for the estimated parameter, and the cost of the reduction of photons in the post-selection by pre-coupling may not impact the measurement because eliminating the saturation effect of the detector response. In addition, our numerical results show that the scheme with biased quantum weak measurement can obtain a higher sensitivity for rotation velocity measurement than the scheme with standard quantum weak measurement.