突破标准量子极限的非对易多参数联合测量

根据量子力学中的海森堡测不准原理，不能以任意精度同时测准两个非对易物理量，若一个物理量的精度超越了标准量子极限(SQL)，则其共轭物理量的精度会低于SQL。然而，在很多实际应用中，需要同时精确测量两个或多个非对易的物理量。本项目拟采用新型非线性干涉仪，由光学参量放大器代替传统马赫—曾德干涉仪中的线性分束器，实验演示多个非对易物理量的联合测量，使各个物理量的测量精度同时超越SQL。在进行实验研究的同时，还将深入分析多参数联合测量过程中，影响每个参数测量精度的因素，探索多参数联合测量的量子极限。本项目的创新性主要体现在三个方面：1）利用非线性干涉仪实现多参数量子联合测量；2）实验演示三个及三个以上非对易物理量的测量精度可以同时超越标准量子极限，同时精确测量的物理量数目大于目前报道的最大数目2；3）分析多参数联合测量时的量子资源分配和量子极限问题。本项目的成果对于研究多参数量子计量有重要意义。

Heisenberg uncertainty relation in quantum mechanics sets the limit on the measurement precision of non-commuting observables, which prevents us from measuring them precisely in the same time. If the precision of one observable is beyond the standard quantum limit (SQL), the precision of its conjugate will not be able to exceed the SQL. In some applications, however, different non-commuting observables contain valuable information and need to be measured simultaneously. We propose to jointly measure two or more non-commuting variable by using the newly developed nonlinear interferometer, which is formed by replacing the two linear beam splitters of the traditional Mach-Zehnder interferometer with two optical parametric amplifiers. For the joint measurement accomplished by the nonlinear interferometer, the precision of each observable is simultaneously beyond the SQL. In addition to conducting the experimental investigation, we will analyze the factors influencing the precision of each observable and explore the quantum limit of the multi-parameter joint measurement. The innovations of our proposal are the following. (1) Experimentally study the multi-parameter joint measurement by using the nonlinear interferometer. (2) Experimentally demonstrate the joint measurement of three non-commuting observables, the number of the observables with precision simultaneously beyond SQL is greater than the current record of two. (3) Theoretically analyze the quantum limit and quantum resource problem when the joint measurement of multi-parameters are performed. The proposed investigation is very important for multi-parameter quantum metrology.