Monroe Jonathan T, Yunger Halpern Nicole, Lee Taeho, Murch Kater W
Department of Physics, Washington University, St. Louis, Missouri 63130, USA.
ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA.
Phys Rev Lett. 2021 Mar 12;126(10):100403. doi: 10.1103/PhysRevLett.126.100403.
Traditional uncertainty relations dictate a minimal amount of noise in incompatible projective quantum measurements. However, not all measurements are projective. Weak measurements are minimally invasive methods for obtaining partial state information without projection. Recently, weak measurements were shown to obey an uncertainty relation cast in terms of entropies. We experimentally test this entropic uncertainty relation with strong and weak measurements of a superconducting transmon qubit. A weak measurement, we find, can reconcile two strong measurements' incompatibility, via backaction on the state. Mathematically, a weak value-a preselected and postselected expectation value-lowers the uncertainty bound. Hence we provide experimental support for the physical interpretation of the weak value as a determinant of a weak measurement's ability to reconcile incompatible operations.
传统的不确定性关系规定了在不相容的投影量子测量中存在最小量的噪声。然而，并非所有测量都是投影测量。弱测量是用于在不进行投影的情况下获取部分状态信息的微创方法。最近，研究表明弱测量服从以熵表述的不确定性关系。我们通过对一个超导transmon量子比特进行强测量和弱测量，对这种熵不确定性关系进行了实验测试。我们发现，一次弱测量可以通过对状态的反作用来协调两次强测量的不相容性。在数学上，一个弱值——一个预选和后选的期望值——会降低不确定性界限。因此，我们为将弱值物理解释为弱测量协调不相容操作能力的决定因素提供了实验支持。
