Hollow-core fibre based quantum optical light-atom interface

自从大约世纪前发现量子力学以来，量子力学的物理定律一直困扰着研究人员，并引起了广泛的兴趣。特别是，对现实和客观性的意义的哲学含义引起了持久的争论。争论的焦点是纠缠的概念，两个遥远的物体，在测量的行为，似乎同意随机测量的结果，虽然没有物理现实可以归因于他们的属性之前的测量，虽然他们之间的任何通信被排除在相对论。在现代，在这一领域取得了巨大的进展，除了大量的装置和应用，如激光和超流体，光子甚至单个原子的纯量子特性现在可以以前所未有的精度控制。虽然这种高水平的控制首先是在量子光学中实现的，即光物理学，但激光冷却的出现也使物理学家能够设计新的物质量子态。这些研究领域分别在1997年、2001年和2005年获得了诺贝尔物理学奖。随着纠缠态在量子计算和密码学中的潜在应用的发现，纠缠态成为了一个引人注目的研究热点。使用量子信息单位或量子比特的设备可以有效地解决某些计算问题，模拟量子动力学，并提供一种完全安全的通信手段。未来量子网络的重要组成部分，即，能够控制量子态的链接节点，将能够连接光和物质。虽然光子可以很容易地传输，但在其本质上是非常不稳定的，但物质的量子态可以被保持，控制和设计为相互作用。一组小型的、易于控制的量子机器可以通过互连变得更强大。远距离量子通信的问题可能是最好的例子。虽然基本的量子通信设备已经商用，但由于任何类型的量子信道都不可避免地引入噪声，目前的技术仅限于约150公里的距离。要克服这一限制，只有在节点能够存储和保存传输的量子信息并对其进行量子操作的情况下，才能在技术上可行。因此，人们对开发完成这些任务的光-物质接口有着浓厚的兴趣。这样的接口也有其他应用。将良好控制的光学状态转移到物质上可以用于精密测量，如磁力测量，原子钟和光谱学。与此同时，可以设计或检测新的光状态，应用包括压缩光，单光子，频率转换以及高效甚至非破坏性光子计数，其中光的强度可以被精确测量而不会被吸收。所有这些都是量子光学应用的一系列广受欢迎的资源。该项目的目的是设计和建造一个光纤光-原子界面通过结合冷原子物理学的技术，我们希望建立一个基于集成空心光子晶体光纤的微制造芯片的系统。在芯片的帮助下，我们将把激光冷却的超冷原子磁限制在这些光导纤维的6微米大小的空芯中，并让它们与光场相互作用。该系统将使我们能够探索新的参数机制，并可能成为具有非常快的切换时间的长寿命（秒）量子存储器的第一个演示。所提出的实现与光纤通信的自然兼容性将使量子通信设备更接近“真实的世界”的实现。

Since their discovery, about a century ago, the physical laws of quantum mechanics have puzzled researchers and attracted widespread interest. In particular, the philosophical implications for the meaning of reality and objectivity have raised lasting debates. The bone of contention being the concept of entanglement, where two distant objects, upon the act of measurement, appear to agree on random measurement outcomes, although no physical reality could be ascribed to their properties before the measurement and although any communication between them is ruled out by the theory of relativity.In modern days, immense progress has been made in this area, and beyond the vast amount of devices and applications such as lasers and superfluidity, the pure quantum properties of photons and even individual atoms can now be controlled with unprecedented precision. While such a high level of control was first achieved in quantum optics, i.e. the physics of light, the advent of laser cooling enabled physicists also to engineer new quantum states of matter. These research fields were recognized by the award of Physics Nobel prizes in 1997, 2001 and 2005.The field became a spectacular topic of interest when potential applications of entanglement for quantum computing and cryptography were discovered. Devices working with quantum units of information, or qubits, could efficiently solve certain computational problems, simulate quantum dynamics, and provide a means for completely secure communication. An important ingredient for future quantum networks, i.e., linked nodes that are capable of controlling quantum states, will be the ability to interface light and matter. While photons can be easily transported but are very volatile in their very nature, quantum states of matter can be kept, controlled, and designed to interact with each other. A set of small, easily controllable quantum machines can become more powerful by interconnection. The problem of long-distance quantum communication might serve as the prime example. While basic quantum communication devices are already commercially available, current technology is limited to distances of about 150 km due to the noise that is inevitably introduced in any sort of quantum channel. Overcoming this limit will become technically feasible only with nodes that are capable of storing and preserving the transmitted quantum information and performing quantum operations on it. Hence, there is a strong interest in developing light-matter interfaces that fulfil these tasks. Such interfaces also find other applications. The transfer of well-controlled optical states onto matter can serve for precision measurements such as magnetometry, atomic clocks, and spectroscopy. At the same time, new states of light can be engineered or detected, and applications include squeezed light, single photons, frequency conversion, and efficient or even non-destructive photon counting, where the intensity of light can be precisely measured without absorbing it. All of these are much sought-after resources for a range of quantum optical applications.The aim of this project is to design and build a fibre optical light-atom interface. By incorporating techniques from cold-atom physics, we want to build a system based on a micro-fabricated chip with integrated hollow-core photonic crystal fibres. With the help of the chip we will magnetically confine laser cooled, ultracold atoms in the 6 micron sized empty core of these light guiding fibres and let them interact with the light field. This system will allow us to explore new parameter regimes and can become the first demonstration of a long-lived (seconds) quantum memory with very fast switching times. The natural compatibility of the proposed implementation with fibre optical communication will bring quantum communication devices closer to a "real world" implementation.