Signals of Quantum Behaviour in Nanomechanical Systems: Non-linear Effects

纳米机械系统中量子行为的信号：非线性效应

• 批准号: EP/D066417/1
• 负责人: Denzil Rodrigues
• 金额: $ 27.79万
• 依托单位: University of Nottingham
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FD066417%2F1
• 关键词: Signals; Quantum; Behaviour; Nanomechanical; Systems

Nanoelectromechanical systems, or NEMS, are an emerging technology where tiny machines (such as vibrating beams) are built onto silicon chips in the same way as electronics are miniaturised on computer chips. As well as having the same advantages as computer chips, such as reliability, small size and low cost, having mechanical devices on a chip instead of just electronics leads to a wide range of completely novel applications, ranging from optical switches, to car airbag sensors, to weighing scales sensitive enough to measure the mass of a single DNA molecule. However, as well as offering many new technologies, NEMS can also cast light on a question that has puzzled physicists for a century / the quantum to classical transition.NEMS are sometimes described as mesoscopic, or middle-sized, as they are tiny compared to the everyday world, but still much larger than atoms. Since the start of the 20th Century, we have known that atoms obey very different rules to everyday objects like footballs, rules that are known as quantum mechanics. As everything is made of atoms, we are left with the question of why a single atom obeys quantum mechanics, but a football made of many atoms obeys the everyday rules of classical mechanics. NEMS devices, being middle-sized, are on the border between the quantum and classical worlds and so are the ideal devices to help us understand the quantum to classical transition.The vast majority of previous work on NEMS has used the most basic descriptions of the devices / namely that they are harmonic oscillators weakly (i.e. linearly) coupled to measuring devices. There are two major problems with this approach. The first is that no oscillator is truly harmonic and no coupling is truly linear, and there will always be corrections to these approximations. As NEMS devices are made smaller and smaller, these corrections become more and more significant, meaning that the simple, linear, description is not good enough. The second problem is that if the oscillator is harmonic and the coupling is linear, there are few obvious differences between the quantum and classical regimes. In particular, it is very difficult for an experimentalist to detect if such an oscillator is behaving quantum mechanically or not.This project will move beyond the well known harmonic, weakly coupled approximation, to include non-linear effects in the coupling and the resonator restoring force. By moving into this as-yet poorly understood area, this project will not only provide a description of NEMS that is more accurate and valid for smaller devices, but will allow the investigation of the differences between the classical and quantum regime. The project will search for clear signals that a device is acting quantum mechanically, by studying effects known as quantum non-demolition, quantum Duffing resonances, and quantum chaos. Such signals will be crucial for experimentalists to be able to state with confidence that they have observed quantum behaviour in a device. In addition, by investigating how these effects change with increasing resonator size and measurement strength, this project will describe how the quantum world of atoms and electrons gives way to our everyday world of footballs.

纳米机电系统（NEMS）是一种新兴技术，将微型机器（例如振动梁）构建在硅芯片上，就像电子产品在计算机芯片上小型化一样。除了具有与计算机芯片相同的优点（例如可靠性、小尺寸和低成本）之外，在芯片上安装机械设备而不仅仅是电子设备还可以带来各种全新的应用，从光学开关到汽车安全气囊传感器，再到足够灵敏以测量单个 DNA 分子质量的秤。然而，除了提供许多新技术外，NEMS 还可以解决困扰物理学家一个世纪的问题/量子到经典的转变。NEMS 有时被描述为介观或中等大小，因为它们与日常世界相比很小，但仍然比原子大得多。自 20 世纪初以来，我们就知道原子遵循与足球等日常物体截然不同的规则，这些规则被称为量子力学。由于一切都是由原子组成的，我们剩下的问题是为什么单个原子遵守量子力学，但由许多原子组成的足球却遵守经典力学的日常规则。 NEMS 设备是中型的，位于量子世​​界和经典世界之间的边界，因此是帮助我们理解量子到经典转变的理想设备。NEMS 的绝大多数先前工作都使用了设备的最基本描述/即它们是与测量设备弱（即线性）耦合的谐振子。这种方法有两个主要问题。首先，没有振荡器是真正的谐波，也没有耦合是真正的线性，并且总是会对这些近似值进行修正。随着 NEMS 设备变得越来越小，这些修正变得越来越重要，这意味着简单的线性描述不够好。第二个问题是，如果振荡器是谐波并且耦合是线性的，则量子和经典体系之间几乎没有明显的差异。特别是，实验人员很难检测这样的振荡器是否具有量子力学行为。该项目将超越众所周知的谐波、弱耦合近似，以包括耦合和谐振器恢复力中的非线性效应。通过进入这个目前还知之甚少的领域，该项目不仅将提供对较小设备更准确和有效的 NEMS 描述，而且将允许研究经典体系和量子体系之间的差异。该项目将通过研究量子不可破坏、量子达芬共振和量子混沌等效应，寻找设备以量子力学方式起作用的明确信号。这些信号对于实验者能够自信地声明他们已经观察到设备中的量子行为至关重要。此外，通过研究这些效应如何随着谐振器尺寸和测量强度的增加而变化，该项目将描述原子和电子的量子世界如何让位于我们日常的足球世界。