Asymmetric Fermi Superfluids and Engineered Quantum Systems

非对称费米超流体：电子有两种类型——自旋向上和自旋向下。在超导体中，每个自旋向上的电子与一个自旋向下的电子结合，形成所谓的库珀对。它们负责导电而不耗散。问题来了——当自旋向上的电子比自旋向下的电子多时会发生什么？什么是最好的方式来容纳额外的自旋向上的？四十多年后的今天，我们发现这是一个极其困难且仍未解决的问题。最近我们有了一个新的实验系统——原子（而不是电子）的冷气体，它表现出与超导体相同的物理特性，而且实验比用电子更容易进行和解释，所以我们有真正的机会解决这个难题。我们还可以问，如果不使用不同的自旋，而是将不同质量的原子配对，会发生什么——这个问题不容易用电子来回答。我的研究将有助于解释在寻找这些系统中预期出现的物质的新阶段的实验。进一步，我希望在问题解决的最后能够提供一个统一的理论框架。工程量子系统：1)非平衡物理——冷原子非常慢，我们可以改变它们在实验室中经历的条件，比它们反应的时间还快！我们也可以拍摄他们的行动。这使我们能够研究它们在对我们所做的事情（比如压缩它们，突然给它们更多的能量，等等）做出反应时重新排列自己时所经历的复杂运动。这是一个新领域，因为其他系统（如电子和金属）通常运动得太快，我们无法看到它们在做什么。这也是探索所谓的多体量子力学的一种新方法——当有许多原子在一个时间依赖的情况下会发生什么。2)量子信息接口——量子计算的最新进展提出了混合量子计算的想法。有些系统（比如俘获离子）对于量子位来说是非常好的存储器。其他的（如实体statenanostructures）作为cpu工作得很好。我们如何在它们之间传输量子比特，哪个系统耦合最好？我建议研究各种各样的原子-固体系统，以寻找最好的界面技术，这有望在不久的将来成为一个重要的研究领域。

Asymmetric Fermi Superfluids: electrons come in two types - called spinup and spin down . In superconductors each spin up electron joins a spindown electron to form what is called a Cooper pair. These are responsiblefor conducting electric current without dissipation. The question arises -what happens when there are more spin up than spin down electrons? What isthe best way to accomodate the extra spin up ones? It turns out that thisis an extremely difficult and still open problem after more than fortyyears. Recently we have a new experimental system - cold gases of atoms (instead ofelectrons) which exhibit the same physics as superconductors and theexperiments are much easier to perform and interpret than with electronsso we have a real opportunity to solve this puzzle. We can also ask whatwould happen if instead of playing with different spins we paired atomswith different masses - a question which cannot be easily asked withelectrons. My research will help to interpret experiments in the search for new phases of matter which are expected to appear in these systems. Further, I hope to be able to provide a unified theoretical framework at the end when the problem is solved.Engineered Quantum Systems: 1) nonequilibrium physics - cold atoms arevery slow and we can change the conditions they experience in the labfaster than the time it takes them to react! We can also photograph themin action. This allows us to study the complicated motions that theyundergo as they rearrange themselves in response tosomething that we did (like compressing them, suddenly giving them moreenergy, etc). This is a new field since other systems (such as electronsin metals) usually move too fast for us to see what they are doing. It is also a new way of exploring so-called many-body quantum mechanics - what happens when there are many atoms in a time-dependent situation. 2) interfaces for quantum information - recent progress in quantum computing has proposed the idea of hybrid quantum computing. Some systems (liketrapped ions) are very good memories for qubits. Others (like solid statenanostructures) work very well as CPUs. How do we transfer qubits betweenthem and which systems couple best? I propose to study a variety ofatom-solid state systems in search of the best interface technology inwhat promises to become a vital area of research in the near future.