Small-Scale Ring Traps for Atom Interferometry and Quantum Fluid Investigations

使用光学干涉仪作为测量的灵敏工具可以追溯到世纪前迈克尔逊和莫利的实验。随着随后激光器的发明，相干光源，光学干涉测量已经发展成为一种普遍存在的技术，用于精确测量位置，加速度和（通过Sagnac效应）旋转等量。在这些技术进步的同时，通过量子力学的发展，人们对物质有了更基本的理解。这里的一个关键概念，与我们的经典理解不一致，是物质的波动性质。人们意识到，实际上原子波只有在极低的温度下才能观察到。然而，激光现在已经提供了实现这一点的工具;原子样本距离绝对零度百万分之一度或更少，实际上也是激光本身的原子等效物，即被称为玻色-爱因斯坦凝聚体的原子相干源，BEC。我们现在有了联合收割机来结合干涉和冷原子这两个概念：原子干涉测量术。然而，关键点是原子干涉测量的范围更广（对例如重力场和电磁场的灵敏度），尤其是上级灵敏度。对于Sagnac干涉仪的灵敏度是成比例的相对论能量的“粒子”，这是通常大于10个数量级的原子比photon.The本建议的目的是开发原子等效的Sagnac干涉仪在重力测量和惯性传感的潜在应用。该平台将是一个完美的圆柱对称环形陷阱，其中BEC可以分为两部分，在相反的方向上移动，然后重新组合，通过累积的相位差揭示外部影响的效果。环形陷阱是基于一个新的概念，我们已经从理论上研究。将金属环置于正弦变化的磁场中。在环中感应出电流，从而在环周围产生磁场。这与原始的感应场一起在环的内部产生了一个光滑、对称和稳定的磁阱，冷原子和BEC可以被捕获。这种几何形状的简单性和鲁棒性使其成为实际测量设备的有吸引力的候选者。下一步是电子化，这一概念是过去几十年电子和电信等技术进步的根源。微制造技术允许器件制造的大规模并行性，这不仅简化了干涉仪的构造，而且提供了测量的冗余和用于校正系统误差的手段。我们计划微制造感应耦合环陷阱，并证明其作为原子干涉仪的实用性。

The use of an optical interferometer as a sensitive tool for measurements dates back to the experiments of Michelson and Morley over a century ago. With the subsequent invention of the laser, the coherent source of light, optical interferometry has been developed into a ubiquitous technology for precision measurements of quantities such as position, acceleration and (through the Sagnac effect) rotation. In parallel with these technological advances a more fundamental understanding of matter was gained through the development of quantum mechanics. One of the key concepts here, at odds with our classical understanding, is the wave nature of matter. It was realised that atomic waves in practice would only be observable at extremely low temperatures. However, lasers have now provided the tools for realising just that; samples of atoms a millionth of a degree or less from absolute zero and indeed also the atomic equivalent of the laser itself, the coherent source of atoms known as a Bose-Einstein condensate, BEC. We now have the tools to combine two concepts of interference and cold atoms: atom interferometry. The crucial points, however, are the wider scope of atom interferometry (sensitivity to e.g. gravitational and electro-magnetic fields) and above all the superior sensitivity. For a Sagnac interferometer the sensitivity is proportional to the relativistic energy of the 'particle' involved, which is typically more than 10 orders of magnitude larger for atoms than for photons.The aim of the present proposal is to develop the atomic equivalent of the Sagnac interferometer with potential applications in gravitational measurements and inertial sensing. The platform for this will be a perfectly cylindrically symmetric ring trap where a BEC can be split in two parts, that traverse in opposite directions and then recombine to reveal the effect of external influences through an accumulated phase difference. The ring trap is based on a novel concept we have investigated theoretically. A metal ring is placed in a sinusoidally varying magnetic field. A current is induced in the ring, which produces a magnetic field around the ring. This together with the original inducing field produces a smooth, symmetric and stable magnetic trap on the inside of the ring, where cold atoms and BEC's can be trapped. The simplicity and robustness of this geometry makes it an attractive candidate for a practical measurement device. The next step involves miniaturisation, the concept at the root of the last few decades' advances in technologies such as electronics and telecommunications. Micro-fabrication techniques allow for massive parallelism of device manufacture, which not only simplifies the construction of interferometers, but also provides redundancy of measurement and a means for correction of systematic errors. We plan to micro-fabricate inductively coupled ring traps and demonstrate their usefulness as atom interferometers.