RUI: CQIS: OP: State-Preparation-and-Measurement Tomography

随着新技术的不断涌现，量子力学即将在许多领域从根本上改变现代技术。当这些出现时，验证技术是必要的，以确保信心和可靠性。该项目的主要目标是开发发现量子系统中发生的错误的新方法，同时使用对这些系统的最小假设。例如，在涉及量子密钥共享的量子通信中，重要的是通信伙伴要确保他们已经成功地共享了一个密钥，而实际上他们并没有。这个项目的核心错误检测方案可以让他们检测到这个错误，同时对他们的设备做出最小的假设。这些实验将推动量子技术从理论可能性走向实际实现。这些实验将由本科生进行，通过让他们接触新兴的研究领域和新技术，为他们的科学事业做好准备。在表征量子系统的实验中进行的两个重要操作是：(i)准备处于特定状态的系统，然后（ii）对这些状态进行测量。状态准备和测量通常是独立的、不相关的操作，在分析数据时通常假设情况就是如此。然而，如果状态准备与测量之间确实存在相关性，则可能从测量数据中得出错误的结论。该项目的主要目标是通过实验证明一种称为环路状态准备和测量（SPAM）断层扫描的技术，该技术能够在做出最小假设的同时检测此类相关误差。除了实验者知道他们正在处理的系统的希尔伯特空间维度外，不需要对状态准备或测量做出任何假设。实验将在单量子比特和双量子比特系统上进行，量子比特编码在单个光子的偏振中。该小组提出证明循环SPAM断层扫描能够检测到单个量子位的状态准备和测量之间的相关性。他们还提议检测两个量子位测量之间的非局部相关性，其中一方试图伪造贝尔不等式违反。

Quantum mechanics is on the threshold of fundamentally changing modern technology in a number of areas, with new technologies emerging regularly. As these emerge, verification techniques are necessary to ensure confidence and reliability. The primary objective of this project is to develop new ways of uncovering errors that occur in quantum systems, while using a minimum of assumptions about those systems. For example, in quantum communication involving quantum key sharing, it is important for the communications partners to be assured that they have successfully shared a secret key, when in fact they have not. The error detection scheme at the core of this project will let them detect this error, while making a minimum of assumptions about their apparatus. The experiments will advance the movement of quantum technologies from theoretical possibility to actual implementation. These experiments will be performed by undergraduate students, preparing them for scientific careers by exposing them to emerging fields of research and new technologies.Two important operations performed in experiments characterizing quantum systems are (i) preparing systems in particular states and then (ii) performing measurements on those states. State preparation and measurement are usually independent, uncorrelated operations, and when analyzing data it is usually assumed that this is the case. However, if there are indeed correlations between the state preparations and the measurements, it is possible to draw erroneous conclusions from measured data. The primary objective of this project is to experimentally demonstrate a technique called loop state-preparation-and-measurement (SPAM) tomography, which is capable of detecting such correlated errors while making a minimum of assumptions. No assumptions need to be made about either the state preparation or the measurements, other than that the experimenter knows the Hilbert space dimension of the system they are working with. Experiments will be performed on one- and two-qubit systems, with the qubits encoded in the polarizations of individual photons. The group proposes to demonstrate that loop SPAM tomography is capable of detecting correlations between state preparations and measurements of single qubits. They also propose to detect nonlocal correlations between measurements of two qubits in which one party is attempting to fake a Bell inequality violation.