Quantum dynamics: Light and matter

量子动力学：光与物质光与物质如何相互作用？这是一个关于量子力学中光子和电子（光和电的粒子）微妙之处的研究建议，当周围有很多电子时，因为物质被压缩，周围也有很多光子，因为光非常强烈。非凡的事情会发生。一些光子可以分裂成两个光子，或者两个光子可以反应形成两个新的光子。这些新光子可以被“纠缠”，即使它们彼此相距数公里，也不会真正独立于另一个光子。许多这样的纠缠对可以形成一个“压缩真空”，光的状态甚至比这更微妙。它们的“非经典性”使它们成为量子信息处理的重要资源。但要使用它们，我们需要能够控制它们。它们应该在“芯片”上，就像我们用于信息处理的电子一样。对于光子，我们如何做到这一点，让它们在散射和其他现实世界不完美的情况下保持它们的非经典性？我们能用它们真正做的事情范围是什么？电子也可以以奇怪的量子力学方式表现，特别是当光与它们相互作用时。在量子力学中，不同的可能结果会相互干扰，就像水波一样，我们可以利用这一点使光速电子向一个方向或另一个方向加速，就像我们选择的那样。然后，就像一辆关掉引擎的汽车，它们会开始减速。但在道路和空气阻力的作用下，它会与其他电子和声音粒子散射。我们能通过这样的实验了解固体中的所有这些“准粒子”吗？我们能用光来控制电吗？如果一个电子有一个确定的速度，量子力学要求它的位置不确定。那么，我们如何看待特定位置的电场“驱动”电子的方式呢？像电阻和电容这样的基本概念有意义吗？随着材料和激光科学的进步，导致固体结构越来越小，光脉冲越来越短，这些现象将是至关重要的，因为量子光子学和电子学合并为一个单一的领域，可能对我们的科学和技术产生深远的影响。所有这些问题的背后都是物理学的基本问题。

Quantum dynamics: Light and matter How do light and matter interact? This is a proposal for research into some of the quantum mechanical subtleties of photons and electrons - the particles of light and electricity - that arise when there are many electrons around, because the matter is condensed, and many photons around as well, due to the light being very intense. Remarkable things can happen. Some of the photons can split into two photons, or two photons can react to form two new photons. These new photons can be "entangled," with neither photon really being independent of the other even if they propagate kilometres away from each other. Many such entangled pairs can make a "squeezed vacuum," and there are states of light even more subtle than that. Their "non-classicalness" makes them an important resource for quantum information processing. But to use them we need to be able to control them. They should be on a "chip," just as are the electrons we use for information processing. How do we do that for photons and have them preserve their non-classicalness in the presence of scattering and other real-world imperfections? And what is the range of things we can really do with them? The electrons can behave in strange quantum mechanical ways too, especially if light interacts with them. In quantum mechanics different possible outcomes can interfere with each other, just as water waves can, and we can use this to make light speed electrons up in one direction or another, just as we choose. Then, like a car with its engine turned off, they will start to slow down. But playing the role of road and air resistance will be scattering with other electrons, and with particles of sound. Can we learn about all these "quasi-particles" in a solid by such experiments? Can we make a useful device using light to control electricity? And if an electron has a definite velocity, quantum mechanics requires that its position is not definite. How then do we think about the way an electric field at a particular position "drives" the electron? Do elementary concepts like resistance and capacitance make sense? As material and laser science progresses, leading to smaller and smaller solid state structures and shorter and shorter optical pulses, these kinds of phenomena will be crucial as quantum photonics and electronics merge into a single field that may have a profound impact on both our science and technology. Behind all of them are fundamental issues in physics.