Non-statistical weak measurements yield weak values that are outside the range of eigenvalues and are not rare, suggesting that weak values are a property of every pre-and-post-selected ensemble. They also extend the applicability and valid regime of weak values.
Physical description of statistical hypothesis testing for a weak-value amplification experiment using a birefringent crystal
我们研究了Ritchie等人[N. W. M. Ritchie,J.G. Story和R. G. Hulet,Phys. Rev. Lett. 66,1107(1991)]的观点,对Susa和Tanaka [Y. Susa和S. Tanaka,Phys.Rev.A92,012112(2015)]。我们得出结论,弱值放大是一个更好的方法来确定是否在实验中使用的晶体是双折射比测量没有后选择,当两个偏振器的角度几乎正交。这一结果给出了一个物理描述和直观的假设检验,并支持弱值放大的实验有用性。
We investigate the measurement uncertainties of a triple of positive operator-valued measures (POVMs) based on statistical distance, and formulate state-independent tight uncertainty inequalities satisfied by the three measurements in terms of triple-wise joint measurability. Particularly, uncertainty inequalities for three unbiased qubit measurements are presented with analytical lower bounds which relates to the necessary and sufficient condition of the triple-wise joint measurability of the given triple. We show that the measurement uncertainties for a triple measurement are essentially dif…
We develop a general theoretical framework for measurement protocols employing statistical correlations of randomized measurements. We focus on locally randomized measurements implemented with local random unitaries in quantum lattice models. In particular, we discuss the theoretical details underlying the recent measurement of the second Rényi entropy of highly mixed quantum states consisting of up to $10$ qubits in a trapped-ion quantum simulator [Brydges et al., Science 364, 260 (2019)]. We generalize the protocol to access the overlap of quantum states, prepared sequentially in an experime…
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 …
Experimental test of Heisenberg's measurement uncertainty relation based on statistical distances
不相容的观测量可以用联合测量中的相容观测量来近似,或者顺序测量,具有海森堡的不确定原理的原始公式所暗示的约束精度。最近,Busch、Lahti和Werner提出了基于测量结果的概率分布之间的统计距离的不准确性权衡关系[Phys. Rev. Lett. 111,160405(2013); Phys.Rev.A89,012129(2014)]。在这里,我们改革他们的理论框架,推导出一个改进的量子比特测量关系,并进行自旋系统的实验测试。该关系揭示了最坏情况下的不准确度从下面被目标观测量的不兼容性紧密地限制,并且通过采用联合测量的实验来验证,在该实验中,同时测量一个量子比特上的两个兼容但典型地非交换的观测量。
We present a general framework of examining the validity of weak measurement -- the standard procedure to acquire Aharonov's weak value -- which has been used intensively in recent years for precision measurement, taking advantage of the amplification mechanism available for the weak value. Our framework allows one to deal systematically with various causes of uncertainties intrinsic to the actual measurement process as well as those found in the theoretical analysis employed to describe the system. Using our framework, we examine in detail the two seminal experiments, Hosten's detection measu…
We investigate a classical statistical model and show that Mermin's version of a Bell inequality is violated. We get this violation, if the measurement modifies the ensemble, a feature, which is also characteristic for measurement processes for quantum systems.
We show that in wavepacket tunnelling localisation of the transmitted particle amounts to a quantum measurement of the delay it experiences in the barrier. With no external degree of freedom involved, the envelope of the wavepacket plays the role of the initial pointer state. Under tunnelling conditions such 'self measurement' is necessarily weak, and the Hartman effect just reflects the general tendency of weak values to diverge, as post-selection in the final state becomes improbable. We also demonstrate that it is a good precision, or 'not really weak' quantum measurement: no matter how wid…