5月19日物理论坛：《Macroscopic Quantum Physics》（宏观量子物理学） [2016-05-16]

报告题目：《Macroscopic Quantum Physics》（宏观量子物理学）

报告人：Vlatko Vedral（牛津大学）

报告时间：2016年5月19日（周四）晚7:30

报告地点：东区理化大楼一楼科技展厅

报告摘要：

Quantum mechanics is commonly said to be a theory of microscopic things: molecules, atoms, subatomic particles. Most physicists, though, think it applies to everything, no matter what the size. The reason its distinctive features tend to be hidden is not a simple matter of scale. Over the past few years experimentalists have seen quantum effects in a growing number of macroscopic systems. The quintessential quantum effect, entanglement, can even occur in large systems as well as warm ones - including living organisms - even though molecular jiggling might be expected to disrupt entanglement.

Different methods for quantifying the quantum and classical parts of correlations are amongst the most actively-studied topics of quantum physics over the past decade. Entanglement is the most prominent of these correlations, but in many cases disentangled states exhibit non-classical behavior too. Thus distinguishing quantum correlations other than entanglement provides a better discriminator between the quantum and classical worlds.

I will first review different notions of classical and quantum correlations quantified by quantum discord and other related measures. However, distinguishing classical from quantum behavior at the macroscopic scale also requires a good measure of `quantum macroscopicity’. I will suggest that macroscopicity should be quantified in terms of coherence, a topic that has seen a number of recent developments. At the end of my presentation I will illustrate these related quantum concepts using a number of state of the art experiments aiming at creating larger and larger quantum superpositions. I will close by discussing an experiment with organic molecules (see Fig) conducted in my group and aimed at probing quantumness at the macroscopic level.

Fig. A typical experimental set up to entangled two physical systems (in this case organic molecules trapped in cavities). The laser provides light whose non-classical properties are then transferred to the molecules through light-matter interaction.

　　量子力学通常被认为是微观世界的理论，例如分子、原子、亚原子。然而大多数物理学家，相信它是普适理论，无论在多大的尺度。物理世界的量子特性不是关乎尺度的简单问题。在过去的几年里实验家们逐渐发现在越来越多的宏观系统中存在的量子效应。典型的量子效应，纠缠，甚至可以发生在宏观体系中 - 包括活的生物体 - 即使分子运动可能会破坏量子纠缠。

　　通过不同的方法来量化描述量子和经典关联是过去十年来量子物理学中被关注和被研究最多的课题。纠缠在描述这些关联中是最突出的参量，但在很多情况下非纠缠态仍然会表现出非经典行为。因此，在纠缠之外区分量子相关性提供了量子世界和经典世界之间更好的鉴别。

　　我会先回顾有关量子和经典关联的不同概念，包括量子失谐等。然而，在宏观尺度区分经典和量子行为也需要一个很好的关于“量子宏观强度”的测度。我会建议量子宏观强度应由相干性来量化描述，特别是这一方向在近来取得了一系列进展。之后，我将通过介绍一些可以制备越来越宏观的量子叠加态的假想实验来示例说明以上的量子物理概念。在报告末尾，我会介绍我的小组正在开展的一个利用有机分子进行宏观尺度探测量子行为的实验。

图：一个典型的实验设备用于让两个物理系统发生纠缠（有机分子被放置于空腔中）。激光设备所提供的光，其非经典属性可以通过光与物质相互作用传递到分子上。

报告人简介：

Vlatko Vedral is a Serbian-born (and naturalised British citizen) physicist and Professor of Physics at the University of Oxford and CQT (Centre for Quantum Technologies) at the National University of Singapore and a Fellow of Wolfson College. He is known for his research on the theory of Entanglement and Quantum Information Theory. As of 2012 he has published over 200 research papers in quantum mechanics and quantum information and was awarded the Royal Society Wolfson Research Merit Award in 2007. He has held a Professorship at Leeds, visiting professorships in Vienna and Singapore (NUS) and at Perimeter Institute in Canada. As of 2012, there were over 10,000 citations to Vlatko Vedral's research papers. He is the author of several books, including Decoding Reality.

After completing secondary education at Matematička gimnazija, he received his B.S. and then a Ph.D. degree at Imperial College in 1998. He then was elected Elsag-Bailey post-doctoral research fellow in Oxford. He then held a research fellowship at Merton College Oxford before returning to Imperial College as the Governor’s lecturer to start a quantum information science research group, a position he held from 2000-2004. Before returning to Oxford, he was Centenary Professor of Quantum Information Science at Leeds University 2004-2009. He currently holds a joint appointment as a Professor of Physics and the University of Oxford and CQT (Centre for Quantum Technologies) at the National University of Singapore. He was elected Fellow of Wolfson College in 2009.

　　弗拉特科 韦德尔 ，物理学家，在牛津大学与新加坡国立大学任职教授，主要研究方向是量子信息物理学。截至2012年，他发表了200多篇量子信息方面的学术论文，总引用超过1万次，并于2007年荣获英国皇家学会沃尔夫森优秀奖。著作多本畅销科普书籍，包括《解码现实》(Decoding Reality)。曾于2004－2009年间受聘为英国利兹大学的量子信息科学世纪教授。2009年当选沃尔夫森学院院士。