Enhancing sensitivity of ultrasmall rotation velocity measurements with biased quantum weak measurement

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.