量子計算可能會有什么實際用途呢?

A demonstration of quantum computing’s power is a defining moment for a field prone to hype

對于一個容易被炒作的領(lǐng)域，量子計算能力的展示是一個決定性時刻

“NATURE ISN’T classical, dammit, and if you want to make a simulation of nature you’d better make it quantum mechanical, and by golly, it’s a wonderful problem because it doesn’t look easy.” With those words, in 1981, Richard Feynman, an American physicist, introduced the idea that, by harnessing quantum mechanics, it might be possible to build a new kind of computer, capable of tackling problems that would cause a run-of-the-mill machine to choke. Feynman was right: it has not been easy. Over the past four decades quantum computers have slowly evolved from squiggles on theoreticians’ blackboards to small machines in university laboratories to research projects run by some of the world’s biggest companies.

“自然界并不像經(jīng)典物理學描述的那樣，真見鬼。要想模擬自然，最好用量子力學。天哪，這真是一道太精彩的題，因為一看就不容易。”1981年，美國物理學家理查德·費曼(Richard Feynman)在這番話中提出了這樣一個想法：借助量子力學，也許能打造出一種新型計算機，解決普通計算機可能無力應(yīng)對的問題。費曼說得對，這并不容易。過去40年里，量子計算機慢慢從理論學家畫在黑板上的潦草曲線發(fā)展到大學實驗室里的小機器，再演變成世界上一些最大公司的研究項目。

Now one of those machines, built by researchers at Google, has at last shown what all the fuss is about. It appears to have performed, in just over three minutes, a task that, the researchers estimate, the world’s most powerful classical supercomputer would take around 10,000 years to complete. Google’s machine is a special-purpose device that was designed to solve a contrived problem with few practical uses. But this display of so-called “quantum supremacy” is nonetheless a milestone.

現(xiàn)在，由谷歌的研究人員制造的其中一臺機器終于讓世人得見這件事到底有多了不起。研究人員估計，它在三分多鐘的時間里完成的一項任務(wù)，若用世界上最強大的經(jīng)典超級計算機來干大約耗時一萬年。谷歌的這臺機器是一種專用設(shè)備，旨在解決一項人為設(shè)計的問題，沒有多少實際用途。但這種所謂“量子至尊”的展示仍然具有里程碑意義。

What might quantum computing actually be used for? That question is obscured by the piles of money and hyperbole that surround it. Along with 5G and AI, it is one of the technologies that presidents, of both countries and companies, love to cite. China and America have pledged to invest billions of dollars in it. There is excited talk of a race, and of the riches and power that await the first to seize the “Holy Grail of computing”.

量子計算可能會有什么實際用途呢?這個問題被圍繞在它周圍的大量金錢和夸張的言論所掩蓋。與5G和人工智能一樣，量子計算也被國家首腦和企業(yè)大佬們掛在嘴邊。中國和美國已經(jīng)承諾在該領(lǐng)域投入數(shù)十億美元。人們興奮地談?wù)撝粓龈傎?，以及在此競賽中第一個捧起“計算圣杯”的那一方將收獲的財富和影響力。

Despite the breathlessness, quantum computers are not magical. A rich body of theoretical work proves that they will be potent, but limited. For all the talk of supremacy, quantum computers are not superior in every regard to their classical cousins. Indeed for many tasks they will offer little improvement. Yet for some problems—but only some—clever programmers or mathematicians can create algorithms that exploit the machines’ quantum capabilities. In those special cases, quantum computers offer huge gains, crunching tasks that would otherwise take years or millennia down to minutes or seconds.

盡管如此扣人心弦，但量子計算機并無魔力。大量理論研究證明，它們會非常強大，但仍有局限性。雖然人們都在談?wù)撍闹粮邿o上，但它們并非在所有方面都優(yōu)于經(jīng)典計算機。實際上，它們在許多任務(wù)上能帶來的提升微乎其微。但在有些問題上——僅僅是有些——聰明的程序員或數(shù)學家能創(chuàng)造出算法來利用這些機器的量子能力。在這些特殊的案例中，量子計算機會帶來巨大的收獲，用幾分鐘或幾秒鐘處理完原本需要多年或幾千年才能完成的任務(wù)。

Several of these algorithms have been developed. They offer a glimpse of where quantum computers might excel. In encryption, for example, a quantum machine could quickly untangle the complex maths that underlies much of the scrambling that protects information online. A world with powerful quantum computers, in other words, is one in which much of today’s cyber-security unravels. Tech firms and governments are investigating new foundations for encryption that are not known to be susceptible to quantum computers. But deploying them will be the work of decades.

其中一些算法已經(jīng)被開發(fā)出來，讓人們得以一窺量子計算機的優(yōu)勢所在。例如在加密技術(shù)方面，量子機器可以迅速解開復雜的數(shù)學題，而這些數(shù)學題構(gòu)成了保護網(wǎng)上信息的大部分加擾處理。換句話說，在一個擁有強大量子計算機的世界里，今天的大部分網(wǎng)絡(luò)安全措施都會被攻破?？萍脊竞透鲊谘芯啃碌幕A(chǔ)加密技術(shù)，希望能免受量子計算機的影響。但部署它們要耗費幾十年。

As Feynman pointed out, classical computers struggle to simulate the quantum-mechanical processes that underpin physics and chemistry. Quantum computers could do so with aplomb, a useful trick for developing everything from pharmaceuticals to petrochemicals. Their ability to solve optimisation problems could help financial firms improve their trading algorithms. Artificial-intelligence researchers hope that quantum computers could offer a boost to their algorithms, too.

正如費曼所指出的，經(jīng)典計算機很難模擬作為物理和化學基礎(chǔ)的量子力學過程。量子計算機可以輕松自如地做到這一點，這對于開發(fā)從藥物到石油化工產(chǎn)品的各種物品都很有用。它們在解決優(yōu)化問題上的能力能幫助金融公司改進交易算法。人工智能研究人員也希望量子計算機能改進他們的算法。

For now, though, all that lies in the future. Google’s machine is best thought of as a Sputnik moment. By itself, Sputnik did nothing but orbit Earth while beeping. But it proved a concept, and grabbed the world’s attention. Google’s accomplishment is one in the eye for quantum-computing sceptics. It strongly suggests the promise of quantum technology can be realised in practice as well as theory. And it will draw even more money and attention to a red-hot field. A great deal of engineering work remains before quantum computers can be used for real-world tasks. But that day has suddenly got closer.

不過，現(xiàn)在一切都還未見分曉。谷歌的機器最適合被看作一個史潑尼克時刻。就“史潑尼克號”本身而言，它除了嗶嗶地叫著繞行地球外并沒什么用處。但它證明了一個概念，并吸引了全世界的注意。谷歌的成果打擊了量子計算的懷疑論者。它強有力地表明了量子技術(shù)的前景不僅在理論上成立，在實踐中也能實現(xiàn)。而這將為這個炙手可熱的領(lǐng)域吸引到更多的資金和關(guān)注。在用量子計算機解決現(xiàn)實世界的任務(wù)之前還有大量的工程建設(shè)要完成。但這一天突然離我們更近了。