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Frank Wilczek
弗蘭克·維爾切克是麻省理工學院物理學教授、量子色動力學的奠基人之一。因發現了量子色動力學的漸近自由現象，他在2004年獲得了諾貝爾物理學獎。
作者 | Frank Wilczek
翻譯 | 胡風、梁丁當
中文版
物理學家常常需要從噪音中識別出有用的信號，但在另一些情況下，噪音本身就是信號——這些隨機漲落背後，可能藏著重大科學突破。
19世紀德國哲學家叔本華 (Arthur Schopenhauer) 在《論噪音》一文中寫道：「最有才華的人對任何形式的幹擾、打斷和分心都深惡痛絕，尤其是噪音帶來的折磨。」他說的噪音指的是那些用耳朵聽到的噪聲，尤其是「馬鞭抽打的噼啪聲，讓人憎惡，可以讓頭腦麻痺。」
對科學家來說，噪音是一個更加廣泛的概念，它指代任何具有隨機性的漲落。與噪音相對的是信號。信號傳遞的是人們需要的信息，是有用的。如何從雜亂的背景噪音中分辨出有趣的信號，是實驗科學和統計學的重要組成部分。
但有時，噪音本身就是信號。在1905年這個奇蹟之年，愛因斯坦取得了3項重要發現，其中兩個（分子運動論和光量子假說）都是從噪聲中發現的。而最近，關於噪音的創造性工作再次推動了基礎物理學的一系列突破性進展。
如果在顯微鏡下觀察懸浮在液體中的花粉顆粒，我們會發現它們在做無規則運動。愛因斯坦認為，這種無規則運動是由花粉顆粒受到一個個流體分子的隨機碰撞導致的。基於這個解釋，他能夠為分子的存在提出一個令人信服的依據，並且確定它們的質量。在研究黑體輻射時，愛因斯坦在馬克斯 · 普朗克的研究基礎上，進一步證明了輻射流中的顆粒性意味著光是一份一份的，即量子的。今天，我們稱其為光子。
在日常生活中，我們通常認為電流是平滑的。事實上，電流是由一個個離散的電荷載流子——通常是電子——形成的，這導致電流具有不可消除的顆粒性，即散粒噪聲。散粒噪聲在電流信號很弱的時候尤其明顯，它的強度可以用來測量電子的電荷。1995年，科學家們利用散粒噪聲發現了某些物質態中的帶電粒子只攜帶分數電荷，從而證明了羅伯特·勞克林 (Robert Laughlin) 的驚人預言，並且開闢了一個全新的「亞電子」領域。
今年4月，《科學》雜誌的封面文章宣布，物理學家們探測到了任意子——一種玻色子和費米子之外的第三類亞電子粒子。多年來，理論物理學家一直期待著發現這類粒子。（「任意子」是我在1982提出的名字。）
發現任意子的核心測量涉及到一種更複雜的散粒噪聲 ：它不僅涉及單個電流的漲落，還涉及到兩個電流漲落之間的關聯。這項新的研究帶來了眾多全新的可能性，包括建造更高效的量子計算機。
關於電流的漲落以及它們之間的關聯看上去似乎很深奧，但它們其實是我們思維模式的一個隱秘卻至關重要的組成部分。我們大腦中的信息大部分是通過神經元的放電模式來編碼的，而神經元的放電模式本質上就是電流脈衝。對於流經不同神經元的電流，它們漲落間的相互關聯，承載了我們的感知與思維。
確實，噪音讓人非常難受。我們受傷或發炎的時候會感到疼痛，這往往與受損神經的紊亂刺激有關。而癲癇更是一種神經上的噪音風暴。正如叔本華所寫的 ：「一位具有偉大才華的智者，當其被打斷、擾亂、分心或轉移注意力時，也就與常人無異了。」但是如果噪音被分析和利用，它也可以成為一種寶貴的資源。
英文版
Scientific breakthroughs often depend on discovering the meaning of seemingly random fluctuations.
In his essay "On Noise," the 19th-century German philosopher Arthur Schopenhauer wrote that "the most eminent intellects have always been strongly averse to any kind of disturbance, interruption and distraction, and above everything to that violent interruption which is causedby noise." He was referring to audible sounds, in particular the "infernal cracking of whips… which paralyzes the brain."
Scientists have a wider concept of noise, using the word to describe any kind of flfluctuation that has an element of randomness. Noise contrasts with signal, which is valuable because it conveys sought-after information. Separating interesting signals from obscuring noise is a big part of the art of experimental science and statistics.
Sometimes, however, the noise is the signal. Two of Einstein's three great discoveries in his "miracle year" of 1905 involved learning from noise. Very recently, creative work with noise has once again powered a series of breakthrough discoveries in basic physics.
Einstein traced the jitter of pollen grains, when immersed in flfluids and observed under a microscope, to their random encounters with individual flfluid molecules. This explanation enabled him to make a convincing case for the existence of molecules and to determine their masses. In his work on black body radiation, Einstein built on the work of Max Planck to show that graininess in the radiation's flflow means that light comes in lumps, or quanta. Today, we call the quanta of light photons.
In everyday life, we usually think of an electric current as a smooth flflow. In fact, the flflow involves lumps of charge-electrons, usually-leading to an irreducible graininess in the current, known as shot noise. Shot noise becomes particularly noticeable for weak currents, and its strength can be used to measure an electron’s charge. In 1995, scientists used shot noise to show that in certain states of matter the granules of charge carry only a fraction of the charge of an electron, verifying a startling prediction of Robert Laughlin and opening up a thriving new fifield of "sub-electronics."
Last month, the cover of Science announced that physicists had detected a new third kingdom of sub-electronic particle called anyons, which join the long-established bosons and fermions. Theorists have been looking forward to anyons for many years. (I named them in 1982.)
The crucial observations here concern a more sophisticated version of shot noise, whichin volves not merely flfluctuations in a single current but correlations between flfluctuations in two of them. The new research opens up new worlds of possibilities, including the construction of more effffective quantum computers.
Fluctuating currents and correlations among them might seem like pretty esoteric subjects, but they're a big part of the way we think, under the hood. Information in our brains is largely encoded in fifiring patterns of neurons, which are essentially spiky electric currents. Correlations among flfluctuations in the currents flflowing through difffferent neurons are the information-bearing patterns that embody perception and thought.
Of course, noise can be noisome. The jumbled activation of injured nerves is involved in the pain of wounds or inflflammation. Epilepsy is a mind-storm of noise, and as Schopenhauer wrote, "a great intellect has no more power than an ordinary one as soon as it is interrupted, disturbed, distracted or diverted." But when noise is mined and harnessed, it can be a valuable resource.
墨子沙龍是以中國先賢「墨子」命名的大型公益性科普論壇，由中國科學技術大學上海研究院主辦，中國科大新創校友基金會、中國科學技術大學教育基金會、浦東新區科學技術協會、中國科學技術協會及浦東新區科技和經濟委員會等協辦。
墨子是我國古代著名的思想家、科學家，其思想和成就是我國早期科學萌芽的體現，「墨子沙龍」的建立，旨在傳承、發揚科學傳統，建設崇尚科學的社會氛圍，提升公民科學素養，倡導、弘揚科學精神。科普對象為熱愛科學、有探索精神和好奇心的普通公眾，我們希望能讓具有中學及以上學力的公眾了解、欣賞到當下全球最尖端的科學進展、科學思想。
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