Coherent Optical and Microwave Physics for Atomic-Scale Spintronics in Silicon (COMPASSS)

硅和随之而来的技术已经给工业、娱乐和通信带来了革命性的变化，人们总是对记忆和处理信息的新方法感兴趣。挑战在于找到以尽可能小的容量对信息进行编码的方法，并以最复杂的方式以最低的能源成本和最高的速度对其进行处理。在这个项目中，我们将开发在单个电子中对信息进行编码的方法，该电子绕硅晶体中的单个杂质原子运行。我们将开发利用信息与邻近杂质电子的磁性连接以太赫兹速度处理信息的技术。同时，我们的工作将产生一种研究原子物理的新方法，这种方法最令人兴奋的是，它要求单个原子通过激光和电磁场的复杂组合被困在真空中。最近对原子物理学的兴趣集中在对原子中量子态的详细控制上。量子物理允许一个电子同时处于两个位置或两个状态，也允许两个电子处于单一纠缠态，在这种状态下，对一个电子的检查会放弃对另一个电子的完全了解。利用脉冲可见光激光对被困在真空中的原子进行的实验证明了基于这一原理的新现象。类似的物理学也适用于原子核，并产生了核磁共振和核磁共振技术。晶体中的杂质，如果它们取代了宿主原子中的一个，有时可以仅仅从它们的额外电荷的角度来考虑。例如，硅晶体中的磷杂质看起来就像硅原子，在原子核中有一个额外的质子和一个额外的电子。额外的电子围绕额外的质子电荷运行，其方式与氢原子中电子围绕质子运行的方式非常相似。允许轨道的能量遵循相同的模式(里德堡系列)，只是跃迁发生在远红外，而不是氢原子的可见光/X射线。我们的计划将扩大原子陷阱和晶体中杂质之间的类比。例如，我们将证明电子可以同时处于两种状态--一种电子版本的触发器，导致薛定谔著名的猫同时活着和死了--它们可以在这种叠加中生活很长时间。最近，原子物理学家一直在试图使用硅技术来操纵原子芯片上方的自由空间中的原子，从而使他们的陷阱最小化。在某种意义上，我们正在研究一个类似的问题，原子就在表面之下，而不是它上面。这样做的好处是，杂质是永久固定的，可以与相邻的杂质形成复杂的和新的分子态，我们可以充分利用世界上最发达的材料的加工技术。这些实验都是由乌得勒支附近的自由电子激光Felix设施实现的。这种激光器(在英国还不存在)类似于用于原子物理实验的脉冲可见光激光器，但发出适合于硅中杂质原子的远红外脉冲。我们的方案利用了Felix提供的相干和可调的非常高功率、非常短的脉冲光这一事实。邻近的杂质电子之间的磁相互作用将通过用Felix激发它们来产生，但为了测量所产生的变化，我们需要微波脉冲和磁体来执行电子顺磁共振(EPR)。为此，我们将在费利克斯安装一台EPR光谱仪。由于EPR被广泛用于测量生物大分子的构型，而远红外激光脉冲可以诱导构象的受控变化，该设备在生物学中也将具有巨大的应用潜力。虽然我们将专注于原子物理，但也会产生一个附带的生物学计划。

Silicon and the technology developed with it has revolutionised industry, entertainment and communication, and there is always interest in new ways to remember and process information. The challenge is to find methods of encoding information in the smallest possible volume and manipulating it in the most complex ways with the lowest energy cost and the highest speed. In this programme, we shall develop methods for encoding information in a single electron, orbiting a single impurity atom in a silicon crystal. We shall develop the technology for manipulating that information with terahertz speed by its magnetic connection with adjacent impurity electrons.At the same time our work will produce a new way of studying atomic physics, which, at its most exciting, requires that single atoms are trapped in a vacuum by complex combinations of laser beams and electro-magnetic fields. Recent interest in atomic physics has centred around the detailed control of quantum states in atoms. Quantum physics allows an electron to be in two places or two states at once, and also allows two electrons to be in a single entangled state where examination of one electron gives up full knowledge of the other. Experiments with pulsed visible lasers on atoms trapped in vacuum have demonstrated new phenomena based on this principle. Similar physics applies to the nucleus, and has resulted in the technology of NMR and MRI. Impurities in crystals, if they have substituted one of the host atoms, can sometimes be thought of just in terms of their extra charge. For example, phosphorus impurities in silicon crystals look like silicon atoms with an extra proton in the nucleus and an extra electron. The extra electron orbits around the extra proton charge in a very similar way to the orbit of the electron around a proton in a hydrogen atom. The energies of the allowed orbits follow the same pattern (the Rydberg series) except that the transitions are in the far-infrared, as opposed to the visible/X-rays for hydrogen. Our programme will extend the analogy between the atom trap and the impurity in a crystal. For example we will demonstrate that electrons can be put into two states at once - an electronic version of the trigger that caused Schrodinger's famous cat to be both alive and dead at the same time-and that they can live in this superposition for long times. Recently, atomic physicists have been trying to minaturise their traps using silicon technology to manipulate the atoms in free space just above an atom chip . In a sense, we are working on a similar problem with the atoms held just below the surface instead of just above it. This has the advantage that the impurities are permanently fixed, that complex and new molecule states can be made with adjacent impurities, and that we can take full advantage of the processing technologies in the world's best developed material. The experiments are all enabled by the Free-Electron Laser FELIX facility near Utrecht. This kind of laser (which does not yet exist in the UK) is analogous to the pulsed visible lasers used for the atomic physics experiments, but gives out far-infrared pulses suitable for impurity atoms in silicon. Our proposal takes advantage of the fact that FELIX provides very high power, very short pulsed light that is coherent and tunable. The magnetic interactions between adjacent impurity electrons will be produced by exciting them with FELIX, but to measure the resulting changes we need microwave pulses and a magnet to perform electron paramagnetic resonance (EPR). We will install an EPR spectrometer at FELIX for this purpose. The equipment will also have enormous potential for applications in biology, since EPR is used extensively for measuring the configuration of large bio-molecules, while far-infrared laser pulses can induce controlled changes in conformation. Although we will concentrate on the atomic physics, a spin-out programme in biology will result.