基于压缩光的量子精密测量

Quantum precision measurement based on squeezed light

对任何物理量的测量都有一定的噪声,经典测量所能达到的最小噪声一般称为散粒噪声,对应着测量的标准量子极限.利用压缩光可以突破标准量子极限,从而提高测量精度.本文介绍了压缩态光场用于突破标准量子极限的基本原理,以及压缩态光场在相位测量、光学横向小位移及倾斜测量、磁场测量以及时钟同步等精密测量领域的应用和最新进展.

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 nonclassical 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.This review focuses on the following four kinds of precision measurements based on squeezed light： the measurements of relative phase,small lateral displacement and tilt,magnetic field,and clock synchronization.For all of these measurements,vacuum squeezing has been used to enhance measurement precision,while the types of squeezing（squeezing angle,transverse mode,polarization etc.） are different.For phase measurement,quadrature squeezing is injected into the conventionally unused input port of Mach-Zehnder interferometer（MZI） or Michelson interferometer（MI）.For displacement or tilt measurement,a vacuum squeezing beam of a special transverse mode is coupled into an intense coherent beam,yielding a spatial-squeezed light whose transverse position or tilt angle noise is lower than that of a classical light beam.Based on the Faraday effect of polarization rotation,the magnetic field can be detected precisely.The precision can be increased further by using the polarization squeezing.The polarization squeezing can be generated by coupling two orthogonal polarized beams together,a coherent beam and a vacuum squeezed beam.Various polarization squeezing can be illustrated on the Poincaré sphere.Finally,in the clock synchronization based on the optical frequency comb,squeezed light can be used to enhance the time measurement precision.A theoretical scheme with multimode squeezing of supermode（a kind of mode describing the frequency mode of a pulse laser beam） is introduced.The squeezing has extensively been applied into the quantum precision measurements such as gravitational wave detection as well as biological measurement and will play a more important role in the near future.