The US National Security Agency is building a quantum computer to break the encryption that keeps messages secure, reports the Washington Post. The NSA project came to light in documents passed to the newspaper by whistle-blower Edward Snowden. The spying agency hopes to harness the special qualities of quantum computers to speed up its code-cracking efforts. The NSA is believed to have spent about $80m (￡49m) on the project but it has yet to produce a working machine. If the NSA managed to develop a working quantum computer it would be put to work breaking encryption systems used online and by foreign governments to keep official messages secure, suggest the documents excerpted in the Post. The quantum computer is being developed under a research programme called Penetrating Hard Targets and is believed to be conducted out of a lab in Maryland. Many research groups around the world are pursuing the goal of creating a working quantum computer but those developed so far have not been able to run the algorithms required to break contemporary encryption systems. Current computers attempt to crack encryption via many different means but they are limited to generating possible keys to unscramble data one at a time. Using big computers can speed this up but the huge numbers used as keys to lock away data limits the usefulness of this approach. By contrast, quantum computers exploit properties of matter that, under certain conditions, mean the machine can carry out lots and lots of calculations simultaneously. This makes it practical to try all the possible keys protecting a particular message or stream of data. The hard part of creating a working quantum computer is keeping enough of its constituent computational elements, called qubits, stable so they can interact and be put to useful work. The NSA is not believed to have made significant breakthroughs in its work that would put it ahead of research efforts elsewhere in the US and Europe. However, the documents passed to the Post by Edward Snowden suggest the agency's researchers are having some success developing the basic building blocks for the machine. 相關內容 美國國家安全局希望利用這種特殊的量子計算機加快其密碼*工作。 據信美國國家安全局已為該項目投資了約8000萬美元（約合4900萬英鎊），但仍未生產出一臺能夠工作的機器。 據《華盛頓郵報》引用的文件透露，如果美國國家安全局成功研發(fā)了量子計算機，那么它將會被投入到*網絡上和外國政府用來保障官方信息安全的加密系統(tǒng)。 美國量子計算機研發(fā)項目被稱命名為“攻克難關”（Penetrating Hard Targets），據說該項目正在馬里蘭州的一個實驗室內進行。 世界上許多科研小組都志在研發(fā)一臺可工作的量子計算機，但他們至今一直無法成功運行*現在加密系統(tǒng)所需要的算法。 目前的計算機嘗試通過許多不同的方法來*加密，但它們產生的可能的密鑰只能在同一時間內解密一個數據。使用大型計算機可以加速這個過程，但使用龐大的數字來作為密碼將數據加密使得這種方法的有效性大打折扣。 相比之下，量子計算機利用物質的屬性，在一定條件下，這就意味著它可以同時進行很多很多的計算。事實上，這就使得其可以嘗試所有*保護某個特定消息或數據流的密碼。 研發(fā)可工作的量子計算機的難點在于，如何保持被稱為“量子比特”的計算要素足夠穩(wěn)定，使他們能夠運行并付諸有益的工作。 美國國家安全局對于量子計算機的研發(fā)被認為并沒有取得顯著的突破，并沒有使其能夠于美國和歐洲其他地方的研究工作。然而，由愛德華?斯諾登透露給《華盛頓郵報》的文件卻表明，該機構的研究人員在研發(fā)量子計算機基本的組裝模塊方面已取得了一些進展。
