PHOCIS- A Photonic Crystal Integrated Squeezer

近几十年来，物理学家们越来越认识到，控制量子系统的能力将在一系列技术中发挥强大的增强作用，使最知名的经典算法在大量重要的计算问题上黯然失色，并克服测量，传感和成像方面的经典限制。在单个光子的水平上，光也受量子力学规则的支配。随着我们产生、控制和测量光的能力的进步，我们对它作为利用量子现象用于实际目的的平台的潜力的理解也在增长。量子光学已经为我们提供了观测遥远宇宙和解决数学问题的能力，即使是最强大的超级计算机也无法解决这些问题。这些技术需要一个可以编码量子信息的光源。来自所谓的“经典”光源（如激光）的光对于许多测量或通信任务来说是次优的，并且不适合量子计算。因此，需要新的“非经典”光源来打开量子技术的大门。在这个奖学金中，我将建造一种称为“压缩真空”的非经典光源。这种以成对出现的光子为特征的光的状态，已经证明在这些现有的量子光子学演示中是关键的。与早期技术相比，一个关键的改进是这种光源将直接在一段光纤中制造。这将有助于最大限度地减少破坏性损失，从而防止其他压缩真空源投入使用。该设备将结合光纤的一些最新进展：首先，巴斯大学开发的“光子晶体光纤”允许仔细控制产生非经典光所需的关键特性。其次，光纤本身将通过暴露于激光束而被修改，使其具有反射性。这将使我们能够在光纤内创建一个光阱，大大增强产生压缩真空的相互作用。在项目的第二阶段，我将把这个光源与控制系统集成起来，以便对输出光进行实时、主动的操纵。然后，我将把这个输出路由到新型的探测器中，这种探测器能够在真实的时间内测量光束中的量子相关性。通过在该系统的控制和检测阶段之间实现主动反馈，我的目标是汇集“基于测量的量子计算”所需的元素--一个实现量子信息处理全部潜力的实用框架。作为奖励，这项研究将产生超越量子计算的更广泛影响，所开发的方法适用于新的经典光源和先进的领域，如光谱学和成像。

In recent decades, physicists have increasingly understood that the ability to control quantum systems will unleash powerful enhancements across a range of technologies, eclipsing the best known classical algorithms for a plethora of important computational problems and overcoming classical limits in measurement, sensing and imaging. At the level of individual photons, light is also governed by the rules of quantum mechanics. As our ability to generate, control, and measure light progresses, so grows our understanding of its potential as a platform for harnessing quantum phenomena for practical purposes. Quantum optics has already delivered advantages in our ability to observe the distant universe and solve mathematical problems beyond the reach of even the most powerful supercomputers.These technologies demand a source of light into which quantum information can be encoded. Light from so-called "classical" sources, such as lasers, is suboptimal for many measurement or communication tasks and unsuitable for quantum computing. Therefore, new sources of "nonclassical" light are required to unlock the door to the great prizes of quantum technology.In this fellowship, I will build a source of a type of nonclassical light called "squeezed vacuum". This state of light, characterised by photons appearing in pairs, has already proven pivotal in these existing demonstrations of quantum advantage.A crucial improvement over earlier technology is that this source will be fabricated directly inside a single piece of optical fibre. This will help minimise the destructive losses which prevent other squeezed vacuum sources being put to use. This device will incorporate some of the newest advances in fibre optics: Firstly, "photonic crystal fibre", developed at the University of Bath, allows careful control over critical properties necessary for the generation of nonclassical light. Secondly, the fibre itself will be modified by exposure to a laser beam, making it reflective. This will allow us to create a light-trap inside the fibre, greatly enhancing the interaction that generates squeezed vacuum. In the second phase of the project, I will integrate this source with control systems to allow real-time, active manipulation of the output light. I will then route this output into new types of detector with the ability to measure quantum correlations in the beam in real time. By enabling active feedback between the control and detection stages of this system, I aim to bring together the elements necessary for "measurement-based quantum computing"- a practical framework for realising the full potential of quantum information processing.As a bonus, this research will have a wider impact beyond quantum computing, with the methods developed applicable to new sources of classical light and advancing fields such as spectroscopy and imaging.