The White House has blacklisted eight Chinese quantum computing companies amid growing concerns that the technology will allow hackers to easily break into the West’s most sensitive national security systems.

The businesses, which include Quantum CTek and the Hefei National Laboratory for Physical Sciences at Microscale, have been added to the so-called entity list that prevents American companies from working with them.

The US Commerce Department said the companies were among those deemed “to be acting contrary to the national security or foreign policy interests of the United States”.

Quantum computing is attracting increasing attention in defence circles as the technology moves closer to being useful. 

The computers promise to outpace today’s supercomputers by using an architecture that relies on quantum mechanics, allowing them to perform many more calculations at once. 

It is feared they may soon be able to break the encryption used to scramble sensitive communications and protect data for the intelligence services, giving a huge advantage to the first country able to use the technology.

The recently-signed Aukus pact between the UK, US and Australia included a pledge to share work on quantum computing.

British ministers have backed quantum research with taxpayer funds and have included quantum computing companies among the areas in which ministers can review deals on national security grounds.

Last week, Boris Johnson said that the UK would build the world’s first general-purpose quantum computer as part of a push to hand Britain a 50pc share of the global market by 2040.

The Commerce Department said it was adding the Chinese companies to the list to prevent US technology “from being used for the People’s Republic of China’s quantum computing efforts that support military applications, such as counter-stealth and counter-submarine applications, and the ability to break encryption or develop unbreakable encryption”.

Other members of the US entity list include Huawei, the semiconductor maker SMIC, and DJI, a drone developer.

The Chinese embassy in Washington said the US “uses the catch-all concept of national security and abuses state power to suppress and restrict Chinese enterprises in all possible means”.