Quantum from Classical: Creation of Quantum States of Motion in Nanomechanical Resonators

众所周知，像棒球或行星这样的宏观物体的物理行为是由牛顿提出的经典物理定律非常准确地描述的，许多人在大一物理课程上都很熟悉这些定律。同样众所周知的是，像原子和分子这样的微观物体的行为是由更加神秘和违反直觉的量子物理定律来描述的。目前尚不清楚的是，经典行为和量子行为之间的界限究竟在哪里。为了调查这个问题，本研究将检查通常表现为经典行为的机械系统的行为，目标是使它们表现为量子力学。这将通过使用超导装置在光和机械谐振器之间产生非常强的耦合来实现；光将被用来诱导和读出量子行为。这类研究将更好地划定经典物理学和量子物理学之间的界限，并帮助我们理解量子现象对我们周围日常世界的影响。本项目将资助两名研究生，对其进行微波测量、纳米尺度制造和低温物理等在学术界和高科技行业中广泛应用的实验技术的培训。技术摘要：本基金支持的研究将通过研究由小型机械谐振器与超导微波腔强耦合组成的系统来研究经典物理与量子物理之间边界的本质。两者之间的耦合将由一个库珀对晶体管（一种逐个传输库珀对的超导装置）来调节。库珀对晶体管的存在将使腔中的光子与机械谐振器中的量子晶格振动（声子）之间产生非常强的非线性耦合。事实上，这种耦合将是如此强烈，以至于用单个光子测量或影响单个声子应该是可能的。利用这种强的非线性耦合，应该可以利用微波腔中的光子来诱导机械谐振器中的高量子力学运动状态。对这种相互作用的详细研究可以更好地理解量子和经典行为之间的界面。本项目将资助两名研究生，对其进行微波测量、纳米尺度制造和低温物理等在学术界和高科技行业中广泛应用的实验技术的培训。

Non-technical abstractIt is well understood that the physical behavior of macroscopic objects like baseballs or planets is described very accurately by the laws of classical physics developed by Newton and familiar to many from a course in freshman physics. It is equally well understood that the behavior of microscopic objects like atoms and molecules is described by the much more mysterious and counterintuitive laws of quantum physics. What is not clear is exactly where the boundary between classical behavior and quantum behavior lies. In order to investigate this question, this research will examine the behavior of mechanical systems that would normally behave classically, with the goal of causing them to instead behave quantum mechanically. This will be accomplished by using a superconducting device to cause very strong coupling between light and a mechanical resonator; the light will be used to both induce and read out the quantum behavior. Investigations of this sort will better delineate the border between classical and quantum physics, and help us understand the influence of quantum phenomena on the everyday world around us. Two graduate students will be supported by this project, and will be trained in such experimental techniques as microwave measurement, nanoscale fabrication and low-temperature physics that are widely used both in academia and in high-technology industry. Technical abstractThe research supported by this grant will investigate the nature of the boundary between classical and quantum physics by study of systems consisting of a small mechanical resonator strongly coupled to a superconducting microwave cavity. Coupling between the two will be mediated by a single Cooper pair transistor (a superconducting device that transfers Cooper pairs one by one). The presence of the Cooper pair transistor will allow a very strong, nonlinear coupling between photons in the cavity and quantum lattice vibrations (phonons) in the mechanical resonator. This coupling will be so strong, in fact, that it should be possible to measure or influence a single phonon with a single photon. By making use of this strong, nonlinear coupling, it should be possible to use photons in the microwave cavity to induce highly quantum mechanical states of motion in the mechanical resonator. A detailed study of this interaction could lead to a better understanding of the interface between quantum and classical behavior. Two graduate students will be supported by this project, and will be trained in such experimental techniques as microwave measurement, nanoscale fabrication and low-temperature physics that are widely used both in academia and in high-technology industry.