论文标题
量子状态干涉术
Quantum State Interferography
论文作者
论文摘要
量子状态断层扫描(QST)一直是表征未知状态的传统方法。最近,已经实施了许多直接测量方法,以以资源有效的方式重建状态。在这封信中,我们提出了一种干涉方法,其中任何量子状态(无论是混合还是纯)都可以从可见性,相移,相移和平均强度使用单个射击测量值(因此,我们称之为量子态看术)。这为我们提供了量子状态估计的“黑匣子”方法,其中,在光子的发生率和态信息的提取之间,我们没有改变设置内的任何条件,从而为我们提供了对量子状态的真实单拍估计。相比之下,标准QST至少需要两个测量纯状状态量子,以及至少三个测量混合状态量子置量重建的测量值。然后,我们继续证明,QSI比QST更有效,用于量化纯二分子中的纠缠。我们使用光自由度的极化程度在实验中以高保真度实现了我们的方法。还介绍了该计划的范围涉及$ d-1 $干涉图的纯状态,以$ d $维系统。因此,在我们方法的Qudit方案中,缩放增益更加戏剧化,相比之下,标准QST没有任何假设,大致比例为$ d^2 $。
Quantum State Tomography (QST) has been the traditional method for characterization of an unknown state. Recently, many direct measurement methods have been implemented to reconstruct the state in a resource efficient way. In this letter, we present an interferometric method, in which, any qubit state, whether mixed or pure, can be inferred from the visibility, phase shift and average intensity of an interference pattern using a single shot measurement -- hence, we call it Quantum State Interferography. This provides us with a "black box" approach to quantum state estimation, wherein, between the incidence of the photon and extraction of state information, we are not changing any conditions within the set-up, thus giving us a true single shot estimation of the quantum state. In contrast, standard QST requires at least two measurements for pure state qubit and at least three measurements for mixed state qubit reconstruction. We then go on to show that QSI is more resource efficient than QST for quantification of entanglement in pure bipartite qubits. We experimentally implement our method with high fidelity using the polarisation degree of freedom of light. An extension of the scheme to pure states involving $d-1$ interferograms for $d$-dimensional systems is also presented. Thus, the scaling gain is even more dramatic in the qudit scenario for our method where in contrast, standard QST, without any assumptions, scales roughly as $d^2$.