撰文 | Frank Wilczek澳门永利在线

翻译 | 胡风、梁丁当

汉文版

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 · 奥威尔笔下陈腐狠毒的政权的长远缩影。若是把它玄机地调节一下，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。若是咱们能机灵地诈欺无知，它不错成为一种超才略，使咱们的感官更利害（通过测量仪器），念念维更轩敞（通过臆测机）。

这条口号看似鬻矛誉盾，其根源却在于量子现实的践诺，它从根蒂上对咱们所了解的大肆物体的特质施加了限制。若是咱们掌执所相对于物体景色的表面常识，那么咱们就能够准确地揣度，在测量物体的位置与通顺速率时，它出面前某个处所以及具有某个速率的概率。可是，字据量子表面，位置的蒙胧度与动量的蒙胧度的乘积必须大于一个极限值。这即是海森堡省略情味旨趣。

面前，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微的时空诬蔑。为了最大章程地减少位置测量的邪恶，同期不违背海森堡旨趣，咱们需要尽可能地加多动量的蒙胧度。这种测量艺术被称为“量子压缩”，它是刻下热点的前沿商榷畛域。

要想制造出性能优厚的量子臆测机，最主要的费事在于若何让它经久保持对我方的景色一无所知。经典臆测机在运行经过中会经过一系列的“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代表晶体管的两种景色。与之相对的是，量子臆测机的臆测单位就像量子粒子同样，它不错同期处在通盘这些位置上。

要想确保量子臆测机能够可靠地运行，这种位置的蒙胧性是必要的。因为只好这么，臆测机才气在动量蒙胧度较小的情况下准确地实施下一步要道。若是臆测机意外表示了位置散播的信息，就会镌汰位置的蒙胧度。字据省略情味旨趣，这势必会导致动量蒙胧度升高，从而扯后腿要道实施的可靠性。

在我刚运鼎新念考若何诈欺量子天下的省略情味——某种进度上，也不错被称为“无知”——的时间，我依然觉得这是量子天下很是的奇特表象。但我迟缓厚实到这是一个更为宽泛的见识，它清澈地揭示了咱们与周围天下疏通的许多神志其实并不简便。

比如，让咱们想一想咱们时时是何如鉴识出某个东谈主的。当光子投射到视网膜上，尔后经大脑处理产生的图像会受到诸多成分的影响，比如这个东谈主的位置、朝向、她是否被其它物体装潢、她的衣裳等等。尽管如斯，咱们仍然能够判断出“这是贝茜”。昭彰，在这个经过中咱们遴选性地忽略了许多细节，而这么作念是故意的。

还有一个问题也裸露着无知的价值 ：为什么不是通盘东谈主齐有完满的音准呢？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（践诺上是特定的毛发）来对特定的曲调产生反应。通过这种神志，耳朵不错收罗到通盘的信息，但只好少许一部分东谈主能够彻底诈欺它们。对于咱们这些莫得完满音准的东谈主来说，卤莽大脑在运作时，无刚毅地“遴选”了无知——冷落那些曲调的信息，好让咱们专注于愈加灵验的信息上。

在圣经故事中，亚当和夏娃因为吃了“折柳善恶树”上的果实而受到管理。岂论你何如看待这个故事，它齐无邪地辅导咱们 ：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教师、量子色能源学的奠基东谈主之一。因发现了量子色能源学的渐近开脱表象，他在2004年取得了诺贝尔物理学奖。

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