Unitary CFT description of DQCP is denied from quantum entanglememt entropy

The research team developed a new and more efficient quantum algorithm of the Monte Carlo techniques adopted by scientists to measure the Renyi entanglement entropy of objects. With this new tool, they measured the Rényi entanglement entropy at the DQCP and found the scaling behaviour of the entropy, i.e. how the entropy changes with the system sizes, is in sharp contrast with the description of conventional LGW types of phase transitions. Continue reading

from Quantum Materials to the Origin of Black Holes

In the time of quantum technology and big data, scientists start to integrate Artificial Intelligence (AI) and computational approaches into the fundament research about our mother Nature and Universe. This series of two lectures will help us to unfold such interesting discovery processes. Dr Zi Yang MENG, Associate Professor at HKU Department of Physics, will explain the important role played by AI and computation in the modern quantum material research in the first lecture. Find more

无愁河上的浪荡汉子们

这个题目乍一看有点儿戏谑,甚至有些许少儿不宜的味道,其实《无愁河的浪荡汉子》是木刻家、画家、作家黄永玉在80多岁时开始写作的以自己为原型的人生自传,目前已经出到第三部。第一部《朱雀城》从传主张序子两岁开始,写他的太婆、爷爷、父亲母亲、姑姑和表叔们——其中一位表叔就是写出《边城》、《长河》和《中国古代服饰研究》的沈从文——一个大家族,和他们生活的朱雀古城(以湘西凤凰为原型),古城的四季时光、风俗民情与繁华时的荣耀。 Continue reading "无愁河上的浪荡汉子们"

A bona fide topological Mott insulator discovered in twisted bilayer graphene model

Imagestacking two sheets of graphene – the 2D form of graphite, or the pencil at your hand – in which the carbon atoms form a hexagonal lattice and twist the top sheet out of alignment with the sheet below, yielding a periodic arrangement of atoms named moiré pattern. Do you know that at a twisted angle of about 1o – people now call it the ‘magic’ angle – the system could exhibit very exotic behaviours such as becoming an insulator, a metal or even a superconductor? Can you imagine the same carbon atom in your pencil (graphite) becoming a superconductor when twisted to the magic angle? It indeed did as people discovered it in 2018, but why? Continue reading

关于纠缠的十四行诗

十四行诗,英文叫Sonnet,老一辈翻译家还曾根据音译翻成商籁体,很好听。其实是欧洲的格律诗,最初是小诗、小歌谣,也不一定十四行,随着历史的演进十四行诗句的格式逐渐被定型下来,而且押韵结构也有了严格的限制。在文艺复兴时的意大利,有了彼特拉克体(Petrarchan Sonnet),音韵优美,以歌颂爱情为主。一般分为两部分,前一部分由两段四行诗组成,韵脚为a-b-b-a,a-b-b-a;后一部分由两段三行诗组成,韵脚为c-d-e,c-d-e。 Continue reading "关于纠缠的十四行诗"

库伦作用无尽期,动量蒙卡寄相思

白石道人姜夔,南宋词人,一生布衣游食四方,存词只有80余首,不算高产(虽然他21岁写下的《扬州慢·淮左名都》入选中学语文课本,诸君可以想想自己21岁时在做什么)。但在他43岁那年的正月里,情感不知为何受到了大的扰动,爆发似的一口气写下一组五首《鹧鸪天》(准确地说是从正月初一到正月十六,从第一首《鹧鸪天 • 丁巳元日》到第五首 《鹧鸪天 • 十六夜出》),曲折地追怀自己生命中一段年轻的爱情,五首皆为精品。 Continue reading "库伦作用无尽期,动量蒙卡寄相思"

Higgs mode via dimensional crossover in quantum magnets

The Higgs mode or the Anderson-Higgs mechanism (named after another Nobel Laureate Philip W ANDERSON), has widespread influence in our current understanding of the physical law for mass ranging from particle physics - the elusive “God particle” Higgs boson discovered in 2012 to the more familiar and important phenomena of superconductors and magnets in condensed matter physics and quantum material research. Continue reading

转角石墨烯的三昧

三昧是佛教里的话,是说修行的人能够止息杂念,心神平静,进入禅定,一窥事物的真谛。我们这些俗人,又生活在俗世,每天都在吃喝拉撒中辗转,应付尚且不足,禅定更不可及,离三昧境盖益远矣。大先生有篇著名的文章,叫《世故三昧》,很短,很有趣,把在人世间难得三昧的窘境和苦境写得通透,感兴趣的读者可以找来看看,一定强过阅读下面带着公式和图表的物理八股。 Continue reading "转角石墨烯的三昧"

瞧!这些发明算法的人

发明量子多体问题算法的人,多与普通人不同。他们身上有一种得道高僧、终南隐士的先知之气,往往想要扬弃和重新评价流俗所看重的种种价值观念,率性而为以至于不被社会所理解,甚至被视为狂士和疯子。这其中的原因,恐怕还是来自于在量子多体问题中发明算法本身的难度。Continue reading

我爱纠缠如秋裤

科学研究当然也是揭示规律性的活动,从事这个行业的,也颇有一些愿意思考的人。有趣的是,在笔者熟悉的量子多体系统的研究中,竟也存在一个和秋裤颇为相像的事物,揭示出量子多体系统中无处不在的量子纠缠这样深刻的道理,让科研从业者中愿意思考的人安心,忘却身边的种种不顺遂,进入“此中有真意”的境界而更加起劲地探索其中的奥妙。他们发现通过秋裤的视角可以揭示量子多体系统从朗道—金兹堡对称性自发破缺,到量子相变,再到拓扑序长程纠缠和范畴对称性等等奇异的现象,秋裤之功善莫大焉。 Continue reading "我爱纠缠如秋裤"