经济学人下载:华尔街新宠--量子计算(3)

All this is promising. But quantum financiers acknowledge that, for now, hardware is a limitation. "We're not yet able to perform these calculations at a scale where a quantum machine offers a real-world advantage over a classical one," says Mr Biercuk. One rough way to measure a quantum computer's capability is its number of "qubits", the analogue of classical computing's 1-or-0 bits. For many problems a quantum computer with thousands of stable qubits is provably far faster than any non-quantum machine that could ever be built—it just does not exist yet. 

所有这些前景无限。但采用量子技术的金融家也承认，目前硬件是软肋。“量子计算机目前的运算规模还是太小，不足以在真实世界里实现对经典计算机的优势。”比埃库克说。一种粗略衡量量子计算机性能的方法是看它的“量子比特”数量，量子比特类似于经典计算机中的1或0。对于许多计算问题来说，一台拥有数千个稳定量子比特的量子计算机大概要比任何能造出来的非量子机器都要快得多——只是它尚未出现。

For now, the field must make do with small, unstable devices, which can perform calculations for only tiny fractions of a second before their delicate quantum states break down. John Preskill of the California Institute of Technology has dubbed these "NISQS"—"Noisy, Intermediate-Scale Quantum computers". 

目前，量子计算只能将就使用不稳定的小型设备，它们的运算只能维持远远不到一秒的时间，之后其精细的量子态就会坍塌。加州理工学院的约翰·裴士基给这些设备取名为“NISQ”，即“带噪音的中等规模量子计算机”。

Bankers are working on ways to conduct computations on such machines. Mr Zeng of Goldman pointed out that the computational resources needed to run quantum algorithms have fallen as programmers have tweaked their methods. Mr Pistoia points to papers his team has written exploring ways to scale useful financial calculations into even small machines. 

银行家们正想方设法在这类机器上完成运算。高盛的威廉·曾指出，随着程序员不断调整方法，运行量子算法所需的计算资源已经缩减。皮斯托亚称其团队撰写了一些论文，探讨缩小实用金融计算的规模、使之可以在小型机器上运行的方法。

And at some point those programmers will meet hardware-makers coming the other way. In 2019 Google was the first to demonstrate "quantum supremacy", using a 53-qubit NISQ machine to perform in minutes a calculation that would have taken the world's fastest supercomputer more than 10,000 years. IBM, which has invested heavily in quantum computing, reckons it can build a 1,000-qubit machine by 2023. Both it and Google have talked of a million qubits by the end of the decade. 

某种程度上来说，这些程序员将和硬件制造商相遇。2019年，谷歌率先展示了其“量子霸权”，用53个量子比特的NISQ机器在几分钟内便完成了需要世界上最快的超级计算机花费一万多年的时间才能完成的计算。在量子计算领域投入巨资的IBM公司估计自己到2023年可制造出有1000个量子比特的计算机。两家公司都谈到自己在十年内可以达到一百万量子比特。

When might the financial revolution come? Mr Savoie thinks simple algorithms could be in use within 18 months, with credit-scoring a plausible early application. Mr Kondratyev says three to five years is more realistic. But the crucial point, says one observer, is that no one wants to be late to the party. One common worry is that whoever makes a breakthrough first may choose to reap the rewards in obscurity, rather than broadcast the fact to the world. After all, says Mr Biercuk, "that is how high-frequency trading got started". 

这一金融革命究竟何时到来？萨瓦认为简单的算法在18个月内便可投入使用，早期的应用很可能是信用评分。康德拉特耶夫则认为三到五年内实现可能更加现实。但一位观察人士表示，关键是没有人想在这场博弈中落后。大家都担忧的一点是，无论最先取得突破的是谁，它都可能不会将之公之于众，而是选择闷声发大财。比埃库克说，“毕竟高频交易就是这么来的”。