Although quantum computers theoretically have the potential to threaten national security by breaking encryption techniques, even the most advanced quantum computers currently in public existence are too small and too error-prone to achieve this, rendering the bans seemingly pointless.

The UK is one of the countries that has prohibited the export of quantum computers with 34 or more quantum bits, or qubits, and error rates below a certain threshold. The intention seems to be to restrict machines of a specific capability, but the UK government hasn't explicitly stated this.

A New Scientist freedom of information request for the rationale behind these numbers was turned down on national security grounds. France, Spain, and the Netherlands have also introduced export controls with the same specifications on qubit numbers and error rates.

Identical limits across European states might suggest a European Union regulation, but that isn't the case. A European Commission spokesperson told New Scientist that EU members are free to adopt national measures, rather than bloc-wide ones, for export restrictions.

New Scientist contacted dozens of nations to ask what the scientific basis for these matching legislative bans on quantum computer exports was but was told it was kept secret to protect national security.