Synthesis of Quantum States

微电子和激光是支撑信息时代的两项主要技术，它们只是量子力学理论的相对初级应用。当前研究的一个主要驱动力是实现完全量子衍生信息时代的全部潜力。表达这些未来技术的一个框架是量子信息，它简单地根据潜在的量子态描述它们的操作，以及必须对其进行的操作。不同的量子态产生不同的协议。现有的协议只依赖于非常小的一组态，并且花费了大量的实验努力来产生这些态的高质量版本。然而，生产通常是按照复杂的操作顺序来规定的。在这项研究中，我们将研究一种更自然的产生方法，在这种方法中，适当的量子态的合成嵌入到系统的自然属性中。这将意味着，未来旨在建立新量子技术的实验，将能够以最小的实验努力，以一种容易重复的方式进行自我初始化。这项技术已经知道在特定情况下有效(称为“完美状态转移”)，并且已经在实验中实现。我们的任务是将这种特殊情况扩展到一个更广泛的概念，可以应用于任何量子信息协议。在实践中，这意味着专注于大多数协议所基于的少数特定状态的产生，但也意味着对可以产生的状态的表征可以推动新的理论--如果我们产生了特定的状态，我们可以用它做什么？这一理论概念可能会促进量子技术的更快采用。指定所需的功能是一回事；实验室实现是另一回事，这是由于统称为噪声或消相干的多种外部影响。这些都破坏了完美的概念，意味着最终的产品不是理想的产品。本项目的最后部分将研究如何通过使用系统的进一步工程以及通过将所需功能编码成纠错码的形式来减轻这些影响。最终，人们希望这种消相干可能被用来设计一系列不同于人们在没有它的情况下能够访问的状态，将不想要的方面变成一个基本特征。

Microelectronics and lasers, two of the major technologies underpinning the information age, are but comparatively rudimentary applications of the theory of Quantum Mechanics. A major drive of current research is to realise the full potential of a fully quantum-derived information age.One framework to express these futuristic technologies is Quantum Information, which describes their operation simply in terms of an underlying quantum state, and manipulations that have to be performed on it. Different quantum states yield different protocols.Existing protocols rely on only a very small set of states, and much experimental effort is expended in producing high quality versions of these states. However, production is often specified in terms of a complex sequence of operations. In this research, we will study a more natural production method wherein the synthesis of an appropriate quantum state is embedded in the natural properties of the system. This will mean that future experiments, aimed at building new quantum technologies, will be able to initialise themselves with minimal experimental effort, and in an easily repeated way.This technique is already known to work in specific situations (known as "Perfect state transfer"), and has already been experimentally implemented. Our task is to extend this special case into a broader concept that can be applied to any quantum information protocol. In practice, this means concentrating on the production of those small number of specific states that most protocols are based on, but also means that a characterisation of the states that can be produced can drive new theory - if we produce a particular state, what can be done with it?This theoretical concept could facilitate a far more rapid adoption of quantum technologies than would otherwise be possible. Specifying a desired functionality is one thing; laboratory realisation is another due to the manifold external influences collectively known as noise or decoherence. These corrupt the perfect concept, meaning that the final product is not the desired one. The final part of this project will study how those effects may be mitigated through the use of further engineering of the system, and by encoding the desired functionality into a form of error correcting code. Ultimately, the hope is that this decoherence might be used to engineer a difference range of states from those which one would be able to access without it, turning unwanted aspect into an essential feature.