Investigating coherence of electrons on helium with cavity quantum electrodynamics

电子与液氦有一种独特的相互作用。就像神话中的那喀索斯一样，他们被自己的形象所吸引，但他们被阻止进入液体。相互竞争的作用力，加上量子涨落，导致电子悬浮在表面几纳米以上，在那里它们形成了一个原始的二维电子气体。利用表面下的电极控制电子的运动，最终控制它们的自旋。电子很有希望成为量子信息处理器的量子比特，研究小组也在研究它们形成的独特的量子多体态，即维格纳分子。尽管它是最早发现的二维电子系统之一，但迄今为止还没有对其自旋特性进行检测或其他研究。该团队正在使用最近开发的单电子运动和自旋共振技术来执行这些基本测量。该项目正在开发一种独特的混合量子系统，其中氦上的电子与高精细超导电路相互作用，可以操纵单电子和微波光子。技术描述氦上的电子提供了独特的机会来研究动力学单个电子，它们的自旋和超流体薄膜的激发。本研究将利用一种新的基于腔QED的结构来探索这种二维电子系统的极端迁移率和长相干性。这使得该项目能够利用过去十年在量子信息服务方面取得的进展来研究该系统的基本激励。同样，氦上的电子本身可能具有独特的特性，非常适合量子信息和传感应用。氦上电子的运动与超导量子比特的运动非常相似，因此可以使用许多相同的技术来询问它们，这应该是第一次允许对它们的运动进行连贯的操作。这将是一种独特类型的腔QED系统，它将允许人们深入了解这种独特的二维电子系统的性质和相互作用。该项目试图检测并实现与单个捕获电子的强耦合。此外，该团队将通过向氦池中添加或移除单个电子来构建维格纳分子。氦上的单个电子将被捕获并耦合到超导腔中。计算预测该系统将达到腔量子电动力学（QED）的强耦合极限，即电子可以与单光子相干相互作用。这是对氦上孤立电子相干特性的首次研究。单个捕获电子的自旋特性也在研究中，它似乎也可能达到强耦合极限，在那里自旋光子耦合超过所有相关的退相干速率，并且单个光子的存储和操作成为可能。自旋相干时间的测量将揭示有关磁环境以及电子-氦相互作用的信息。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical abstractElectrons have a unique interaction with liquid helium. Like mythological Narcissus, they are attracted to their own image, but they are prevented from entering the liquid. The competing forces, along with the quantum fluctuations cause the electrons to levitate several nanometers above the surface, where they form a pristine two-dimensional electron gas. The electrons are manipulated using electrodes underneath the surface to control their motion and eventually their spin. The electrons are promising candidates as qubits for quantum information processors and the research team is also investigating unique quantum many-body states they form known as Wigner molecules. Despite being one of the first discovered two-dimensional electron systems,there have been no detections or other studies of their spin properties. The team is using recently developed single electron motion and spin resonance techniques to perform these fundamental measurements. The project is developing a unique hybrid quantum system, in which electrons on helium interact with high finesse superconducting circuits, that can manipulate both single electrons and microwave photons.Technical DescriptionElectrons on helium present unique opportunities to study the dynamics individual electrons, their spins, and the excitations of superfluid thin films. This research will explore the extreme mobility and long coherence of this two-dimensional electron system using a novel cavity QED based architecture. This allows the project to leverage the past decade worth of advances in service of quantum information to study the fundamental excitations of this system. Similarly, electrons on helium themselves may have properties uniquely well-suited to quantum information and sensing applications. The motion of an electron on helium is very analogous to that of a superconducting qubit, so many of the same techniques can be used to interrogate them, which should allow coherent manipulation of their motion for the first time. This would be a unique type of cavity QED system that would allow one to gain insight into the properties and interactions of this unique two-dimensional electron system. The project is attempting to detect and achieve strong coupling to a single trapped electron. In addition, the team will build Wigner molecules by adding or removing individual electrons to a pool of helium. A single electron on helium will be trapped and coupled to the superconducting cavity. Calculations predict that this system will reach the strong coupling limit of cavity quantum electrodynamics (QED) where the electron can interact coherently with single photons. This is the first investigation of coherent properties of an isolated electron on helium. The spin properties of a single trapped electron are also being studied, and it appears possible that it too may reach the strong-coupling limit, where the spin-photon coupling exceeds the all relevant decoherence rates, and single photon storage and manipulation become possible. Measurements of the spin coherence times will reveal information about the magnetic environment as well as the electron-helium interactions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.