撰文 | Frank Wilczek

翻译 | 胡风、梁丁当

中语版

在量子物理中，只好对粒子的动量信息保持无知，才有可能获取它的位置信息。

在乔治·奥威尔（George Orwell）的演义《1984》中，有一句诞妄的口号“无知即力量”。这句口号是乔治 · 奥威尔笔下古老急躁的政权的真切缩影。若是把它玄机地调整一下，改成“无知或为力量”，那这句新的口号就成了如今科技前沿的无邪写真。若是咱们能颖他乡应用无知，它不错成为一种超智商，使咱们的感官更狠恶（通过测量仪器），想维更豁达（通过计较机）。

这条口号看似首尾乖互，其根源却在于量子现实的本体，它从根底上对咱们所了解的苟且物体的特质施加了戒指。若是咱们掌持所关系于物体情景的表面学问，那么咱们就能够准确地推敲，在测量物体的位置与怒放速率时，它出目下某个场所以及具有某个速率的概率。然则，把柄量子表面，位置的疲塌度与动量的疲塌度的乘积必须大于一个极限值。这即是海森堡不细目性旨趣。

皇冠体育

目下，假定咱们要精准地测量某个物体的位置，以探伤引力波引起的轻细的时空污蔑。为了最大戒指地减少位置测量的过错，同期不违背海森堡旨趣，咱们需要尽可能地加多动量的疲塌度。这种测量艺术被称为“量子压缩”，它是现时热点的前沿参谋鸿沟。

要想制造出性能优厚的量子计较机，最主要的穷困在于怎样让它恒久保持对我方的情景一无所知。经典计较机在运行历程中会经过一系列的“位置”，每个位置由一串0和1构成的字符所编码,其中的0和1代表晶体管的两种情景。与之相对的是，量子计较机的计较单位就像量子粒子一样，它不错同期处在通盘这些位置上。

要想确保量子计较机能够可靠地运行，这种位置的疲塌性是必要的。因为只好这么，计较机身手在动量疲塌度较小的情况下准确地实施下一步要领。若是计较机意外显露了位置漫衍的信息，就会裁减位置的疲塌度。把柄不细目性旨趣，这势必会导致动量疲塌度升高，从而龙套要领实施的可靠性。

在我刚运转想考怎样应用量子天下的不细目性——某种进程上，也不错被称为“无知”——的技艺，我一经以为这是量子天下专有的奇特气候。但我缓缓结实到这是一个更为粗俗的意见，它了了地揭示了咱们与周围天下相通的许多神气其实并不简便。

比如，让咱们想一想咱们往往是奈何鉴识出某个东说念主的。当光子投射到视网膜上，此后经大脑处理产生的图像会受到诸多身分的影响，比如这个东说念主的位置、朝向、她是否被其它物体荫庇、她的一稔等等。尽管如斯，咱们仍然能够判断出“这是贝茜”。显豁，在这个历程中咱们遴选性地忽略了许多细节，而这么作念是故意的。

还有一个问题也分解着无知的价值 ：为什么不是通盘东说念主皆有无缺的音准呢？在咱们的内耳中，有一双小小的“反向钢琴”。它们通过拨动特定的键（现实上是特定的毛发）来对特定的调子产生反映。通过这种神气，耳朵不错荟萃到通盘的信息，但只好少许一部分东说念主能够统共应用它们。关于咱们这些莫得无缺音准的东说念主来说，大要大脑在运作时，无执意地“遴选”了无知——漠视那些调子的信息，好让咱们专注于愈加有效的信息上。

在圣经故事中，亚当和夏娃因为吃了“分辩善恶树”上的果实而受到处治。不管你奈何看待这个故事，它皆无邪地指示咱们 ：无知是一项值得属意的遴选。

英文版

The Scientific Value of Ignorance

In quantum physics, maximizing knowledge of a particle’s location requires fuzziness about its momentum, and vice versa.

In George Orwell’s novel “1984,” “Ignorance is Strength” is a shocking slogan that epitomizes a corrupt and sinister regime. But in a more nuanced form, “Ignorance can be Strength,” it is an apt slogan for some cutting-edge science. Used wisely, ignorance can be a superpower that makes our senses more acute and our minds more capacious(through measuring devices and computers, respectively).

This seeming paradox is rooted in the nature of quantum reality, which imposes a fundamental limitation on our knowledge of the properties of any object. Given perfect theoretical knowledge of an object’s state, we can predict probabilities for where it will be found and how fast it will be seen to move, if we measure those things. But according to quantum theory, when we multiply the fuzziness in predicted position by the fuzziness in predicted momentum, the product cannot get below a definite limit. That is Heisenberg’s uncertainty principle.

Now suppose that we’d like to measure the position of a test body very precisely, so that we can detect the tiny distortions of space caused by gravitational waves. To minimize the fuzziness in its position, while remaining in Heisenberg’s good graces, we need to crank up the fuzziness in its momentum. The art of doing this is called “squeezing,” and it is a hot frontier of research.

The main difficulty in making good quantum computers is keeping nature ignorant about what they’re doing. A classical computer runs through a sequence of definite “positions,” each consisting of a series of 0s and 1s that represent the states of its transistors. A quantum computer, like a quantum particle, allows all these positions to coexist.

Fuzziness in position is necessary so that the computer can move reliably, with small fuzziness in “momentum,” to execute the next step in its program. If the computer inadvertently betrays information about its distribution of positions, it will reduce that distribution’s fuzziness and necessarily inject fuzziness into the corresponding momentum, thus making the program’s execution unreliable.

When I first began to think about leveraging ignorance in the quantum world, I considered it to be one of that world’s weird special features. But I’ve come to see it as a much broader idea that illuminates many things about how we deal with the everyday world.

Consider, for example, what it means to recognize someone. The underlying pattern of photons that arrives at our retina will be quite different depending on where that person is, how they’re oriented, whether they’re partially hidden behind other objects, what they’re wearing and many other factors. But in concluding “It’s Betsy,” we choose to ignore all that, and that’s obviously a useful thing to do.

Why don’t we all have perfect pitch? Within our inner ears we have little inverse pianos that move specific keys(actually, specialized hairs)in response to specific tones. The information is there, but few of us can access it. Those of us who don’t have perfect pitch may have “chosen” ignorance—unconsciously, as our brains got wired up—in order to focus on more generally useful relationships.

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Adam and Eve were punished for eating from “the tree of the knowledge of good and evil.” However you take that story, it is a vivid reminder that ignorance is an option worth keeping in mind.

Frank Wilczek

弗兰克·维尔切克是麻省理工学院物理学磨真金不怕火、量子色能源学的奠基东说念主之一。因发现了量子色能源学的渐近解放气候，他在2004年得到了诺贝尔物理学奖。

本文经授权转载自微信公众号“蔻享学术”。

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