量子計(jì)算可能會(huì)有什么實(shí)際用途呢?

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

對(duì)于一個(gè)容易被炒作的領(lǐng)域，量子計(jì)算能力的展示是一個(gè)決定性時(shí)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(xué)描述的那樣，真見(jiàn)鬼。要想模擬自然，最好用量子力學(xué)。天哪，這真是一道太精彩的題，因?yàn)橐豢淳筒蝗菀住?rdquo;1981年，美國(guó)物理學(xué)家理查德·費(fèi)曼(Richard Feynman)在這番話(huà)中提出了這樣一個(gè)想法：借助量子力學(xué)，也許能打造出一種新型計(jì)算機(jī)，解決普通計(jì)算機(jī)可能無(wú)力應(yīng)對(duì)的問(wèn)題。費(fèi)曼說(shuō)得對(duì)，這并不容易。過(guò)去40年里，量子計(jì)算機(jī)慢慢從理論學(xué)家畫(huà)在黑板上的潦草曲線(xiàn)發(fā)展到大學(xué)實(shí)驗(yàn)室里的小機(jī)器，再演變成世界上一些最大公司的研究項(xiàng)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(tái)機(jī)器終于讓世人得見(jiàn)這件事到底有多了不起。研究人員估計(jì)，它在三分多鐘的時(shí)間里完成的一項(xiàng)任務(wù)，若用世界上最強(qiáng)大的經(jīng)典超級(jí)計(jì)算機(jī)來(lái)干大約耗時(shí)一萬(wàn)年。谷歌的這臺(tái)機(jī)器是一種專(zhuān)用設(shè)備，旨在解決一項(xiàng)人為設(shè)計(jì)的問(wèn)題，沒(méi)有多少實(shí)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(jì)算可能會(huì)有什么實(shí)際用途呢?這個(gè)問(wèn)題被圍繞在它周?chē)拇罅拷疱X(qián)和夸張的言論所掩蓋。與5G和人工智能一樣，量子計(jì)算也被國(guó)家首腦和企業(yè)大佬們掛在嘴邊。中國(guó)和美國(guó)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?chǎng)競(jìng)賽，以及在此競(jìng)賽中第一個(gè)捧起“計(jì)算圣杯”的那一方將收獲的財(cái)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(jì)算機(jī)并無(wú)魔力。大量理論研究證明，它們會(huì)非常強(qiáng)大，但仍有局限性。雖然人們都在談?wù)撍闹粮邿o(wú)上，但它們并非在所有方面都優(yōu)于經(jīng)典計(jì)算機(jī)。實(shí)際上，它們?cè)谠S多任務(wù)上能帶來(lái)的提升微乎其微。但在有些問(wèn)題上——僅僅是有些——聰明的程序員或數(shù)學(xué)家能創(chuàng)造出算法來(lái)利用這些機(jī)器的量子能力。在這些特殊的案例中，量子計(jì)算機(jī)會(huì)帶來(lái)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(kāi)發(fā)出來(lái)，讓人們得以一窺量子計(jì)算機(jī)的優(yōu)勢(shì)所在。例如在加密技術(shù)方面，量子機(jī)器可以迅速解開(kāi)復(fù)雜的數(shù)學(xué)題，而這些數(shù)學(xué)題構(gòu)成了保護(hù)網(wǎng)上信息的大部分加擾處理。換句話(huà)說(shuō)，在一個(gè)擁有強(qiáng)大量子計(jì)算機(jī)的世界里，今天的大部分網(wǎng)絡(luò)安全措施都會(huì)被攻破。科技公司和各國(guó)政府正在研究新的基礎(chǔ)加密技術(shù)，希望能免受量子計(jì)算機(jī)的影響。但部署它們要耗費(fèi)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(fèi)曼所指出的，經(jīng)典計(jì)算機(jī)很難模擬作為物理和化學(xué)基礎(chǔ)的量子力學(xué)過(guò)程。量子計(jì)算機(jī)可以輕松自如地做到這一點(diǎn)，這對(duì)于開(kāi)發(fā)從藥物到石油化工產(chǎn)品的各種物品都很有用。它們?cè)诮鉀Q優(yōu)化問(wèn)題上的能力能幫助金融公司改進(jìn)交易算法。人工智能研究人員也希望量子計(jì)算機(jī)能改進(jìn)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(guò)，現(xiàn)在一切都還未見(jiàn)分曉。谷歌的機(jī)器最適合被看作一個(gè)史潑尼克時(shí)刻。就“史潑尼克號(hào)”本身而言，它除了嗶嗶地叫著繞行地球外并沒(méi)什么用處。但它證明了一個(gè)概念，并吸引了全世界的注意。谷歌的成果打擊了量子計(jì)算的懷疑論者。它強(qiáng)有力地表明了量子技術(shù)的前景不僅在理論上成立，在實(shí)踐中也能實(shí)現(xiàn)。而這將為這個(gè)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(jì)算機(jī)解決現(xiàn)實(shí)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。