Quantum measurement
According to the Heisenberg uncertainty principle, the precision of any physical quantity measurement is limited by quantum fluctuation in general, which leads to the so-called standard quantum limit (SQL). The SQL can be beaten by using squeezed light, hence enhancing the measurement accuracy. Squeezed light is a typical non-classical light, it exhibits reduced noise in one quadrature component. Since Caves proposed the scheme of phase measurement enhancement with squeezing, squeezed light has been used to enhance measurement precision in many areas.
Squeezing-enhanced rotating-angle measurement beyond the quantum limit
10/2018
Applied Physics Letter 113, 261103, 2018
Aided by quantum sources, quantum metrology helps to enhance measurement precision. Here, we introduce a method to enhance the measurement of a rotation angle. As a proof of principle, assisted by a quantum state called the squeezed orbital-angular-position (OAP) state and balance homodyne detection, we demonstrate in experiments 3dB-enhanced measurements of a rotationangle beyond the shot noise limit. Furthermore, we discuss means to further improve the measurement with a high-order precision OAP squeezed state. The method holds promise for future practical applications, such as in high-sensitive Sagnac interferometry
Small-displacement measurements using high-order Hermite-Gauss modes
08/2014
Appl. Phys. Lett. 104, 121908, 2014
We present a scheme for small-displacement measurements using high-order Hermite-Gauss modes and balanced homodyne detection. We demonstrate its use with experimental results of displacement measurements using fundamental transverse mode TEM00 and first order transverse mode TEM10 as signal modes. The results show a factor of 1.41 improvement in measurement precision with the TEM10 mode compared with that with the TEM00 mode. This scheme has potential applications in precision metrology, atomic force microscopy, and optical imaging.