Fast reprogrammable photonic experiments for quantum foundational studies

我的博士项目将使用实验和理论的混合方法来研究量子基础。其目的是致力于基础研究，同时考虑量子技术的应用，从而解决这些领域之间的重叠。我将专注于用于量子基础实验的快速可重编程集成光子学。我还会做一些理论工作，其中一些会与实验密切相关，但也会有一些独立的理论项目。我将要研究的量子基础的一个领域是量子因果关系。在量子力学中，事件之间的因果关系可能具有不确定性，就像量子系统的其他物理性质一样，导致不确定的随意顺序[1]。这可能会对我们对时间概念的理解产生重大影响，但它也可以用于量子技术。例如，使用量子比特门顺序的量子叠加的潜在计算优势已经被证明[2]。还研究了量子计量学[3]和通信[4]的可能应用。具有不确定因果顺序的过程已经被实验证明[5]，但为了技术应用，需要创建更复杂的过程的叠加。我要做的第一个项目是我的项目B的直接扩展，这是一个关于更高阶量子因果结构的芯片实验，也就是说，比目前任何实验实现的更多的粒子和更多的顺序排列。我将完成芯片元件的表征，设计印刷电路板，然后进行实验。这可能会占用我第一年的时间。我们计划的另一个项目是颠倒未知单位的实验。由么正运算描述的量子系统的演化在原则上是可逆的，但这只有在么正运算已知的情况下才可能实现。然而，我们往往没有一个完整的物理系统的描述来确定这个一元性。能够在不需要完全理解系统的情况下逆转么正运算，对于研究量子力学中的不可逆性，以及通过逆转系统不想要的演化来消除噪声等实际应用将是有用的。反转单位的协议已经研究过了，我将致力于如何在实验中实现这些协议。该项目将包括设计一个芯片，制造它，然后进行实验。最后，我还计划做一个关于量子计算能量消耗的理论项目。由于需要考虑量子计算的潜在负面影响和资源成本，这一领域最近获得了很多兴趣[6]。它需要理解量子计算操作的量子热力学，以及这与宏观组件的能量消耗之间的关系。这还可能包括研究量子层面上可能存在的能源消耗基本限制。

My PhD project will study quantum foundations using a hybrid approach of both experiment and theory. The aim is to work on foundational studies, whilst considering applications to quantum technologies, thus working on the overlap between these fields. I will focus on fast reprogrammable integrated photonics for use in quantum foundations experiments. I will also do theoretical work, some of which will be closely linked to experimental but also some stand-alone theory projects. One of the areas in quantum foundations that I will be looking at is quantum causality. In quantum mechanics, the causal relations between events can have an uncertainty in a similar way to other physical properties of a quantum system, resulting in an indefinite casual order [1]. This could have a significant impact on our understanding of the notion of time, but it could also be utilised in quantum technology. For example, a potential computational advantage from using a quantum superposition of qubit gate orders has been demonstrated [2]. Possible applications to quantum metrology [3] and communications [4] have also been investigated. Processes with indefinite causal order have been demonstrated experimentally [5], but superpositions of more complex processes will need to be created for technological applications. The first project I will work on is a direct extension of my project B, which is a chip experiment on higher order quantum causal structures, i.e., more parties and more permutations of order than any experimentally achieved so far. I will finish off characterising chip components, design the PCB, and then carry out the experiment. This will likely take up my first year. Another project we have planned is an experiment on reversing unknown unitaries. The evolution of a quantum system described by a unitary operation is in principle reversible, but this is only possible if the unitary is known. However, we often do not have a complete description of a physical system in order to determine this unitary. Being able to reverse a unitary operation without the need to fully understand the system would be useful for studying irreversibility in quantum mechanics, and for practical applications such as removing noise by reversing unwanted evolutions of a system. Protocols for reversing unitaries have been investigated, I will work on how such protocols can be implemented experimentally. The project will involve designing a chip, having it manufactured, and then carrying out the experiment. Finally, I also plan to do a theoretical project on the energy consumption of quantum computing. This area has gained a lot of interest recently, with the need to consider the potential negative impacts and resource costs of quantum computing [6]. It requires understanding the quantum thermodynamics of quantum computation operations, and how this relates to the energy consumption of macroscopic components. This could also include studying possible fundamental limits on energy consumption at the quantum level.