Electron Spins on Liquid Helium for Quantum Computing

传统计算机性能的持续进步正在接近一些困难的基本障碍。量子计算是一种新的信息处理模式，它承诺的性能将超过任何传统计算机，至少在某些问题上是如此。然而，量子计算机很难建造。它们需要精确控制一大群小量子系统之间的相互作用，同时防止它们与环境中的任何其他东西相互作用。电子的磁矩(自旋)很有希望成为小型量子系统的候选者，因为它们与环境的自然相互作用很弱。传统的电子设备通过控制电子的运动来运行，利用这种能力来控制电子自旋之间的相互作用是可能的。然而，与传统电子设备中使用的数千或数百万个电子不同，量子计算机必须被设计成控制每个单独的电子。这项研究涉及控制漂浮在超流液氦表面上方约10 nm真空中的电子。据预测，在这些条件下，自旋相干性将比传统电子器件中电子在固体中运动时长得多。将进行系综脉冲电子自旋共振测量，以测量电子的自旋相干性，或者至少对相干性时间施加下限。实验工作已经表明，含有100个或更少电子的信息包可以可靠地穿过氦表面。将进行实验以隔离、移动和测量氦表面上的单个电子。参与这个项目的学生将学习技能，使他们能够成为多产的研究人员。

The continuing advance in the performance of conventional computers is approaching some difficult fundamental barriers. Quantum computing is a new model for information processing, which promises performance beyond that possible for any conventional computer, at least for certain problems. However, quantum computers are very difficult to build. They require precise control over the interactions amongst a large group of small quantum systems while preventing them from interacting with anything else in their environment. The magnetic moments (spins) of electrons are promising candidates for small quantum systems since they naturally interact only weakly with their environment. Conventional electronic devices operate by controlling the motion of electrons, and it may be possible to harness this ability to control the interactions between the electrons' spins. However, instead of the thousands or millions of electrons which are used in conventional electronic devices, quantum computers must be engineered to control each individual electron.This research involves controlling electrons floating in a vacuum about10nm above the surface of superfluid liquid helium. It has been predicted that under these conditions the spin coherence will be long much longer than when the electrons are moving in a solid as in conventional electronic devices. Ensemble pulsed electron spin resonance measurements will be conducted to measure the electrons' spin coherence, or at least to put a lower limit on the coherence time. Experimental work has already shown that packets with 100 or fewer electrons can be reliably moved across the surface of the helium. Experiments will be performed to isolate, move, and measure individual electrons on the helium surface. The students working on this project will learn skills to enable them to be productive researchers.