Hackers may be able to 鈥渧andalise鈥� other people鈥檚 results on a quantum computer, say researchers, who warn that the problem will only get worse as devices become larger and host more users simultaneously, unless manufacturers plug the security gap.
Sharing access to expensive computing hardware is a common practice, whether on classical supercomputers or exotic quantum chips. Classical devices often run multiple programs for many different users at once, but there are security measures in place to prevent one user from affecting another.
But for quantum computers operating in the same way, at the University of Texas at Austin and his colleagues say it may be possible for someone to interfere with other programs running on the machine. Rather than a specific hacking attack that aims to extract private data, Kumar says this approach is like vandalism: it upsets all the results on the quantum computer without warning users that the results can鈥檛 be trusted.
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鈥淭hey wouldn鈥檛 know what happened,鈥� says Kumar, as the results could appear normal while being incorrect. 鈥淚f you鈥檙e doing it for something critical, it would have really bad implications.鈥�
The team tested the hack on five different cloud-based quantum computers operated by IBM. The firm currently doesn鈥檛 allow multiple users on one machine simultaneously, so the team wrote software designed to mimic multiple programs and users and found that the attack changed other users鈥� outputs 40 per cent of the time.
This proof-of-principle attack shows there is a risk that data integrity may be threatened as quantum computers scale up, as this is likely to lead to sharing of machines to make the most use of the hardware. IBM declined to comment on the work.
The problem is caused by interference in the microwave signals used to control qubits, or quantum bits, in these types of computers, with signals intended for one qubit potentially picked up by another. As computers get larger and qubit counts rise, this interference is likely to become a bigger issue.
Thankfully, Kumar says the team has identified a fix for the issue and that companies need to implement it now. Currently, quantum programs tend to be run many times on the same chip in order to get a valid result. The team says mixing up the various programs so that they are run in different combinations on different chips would drastically reduce the chance of the attack working.
at the University of Oxford says interference is already a serious problem for superconducting quantum computers because of the errors it causes, even before you consider malicious attacks, and the focus of the quantum computer industry at the moment is on getting anything useful to run on any chip, let alone thinking about multiple users. But once quantum computers advance, this is likely to be something that needs to be fixed, he says.
鈥淚 think it鈥檚 probably a reasonable thing to start thinking about early,鈥� says Kissinger. 鈥淭his is something that these kind of architectures are definitely going to have to face if they want to do this kind of multi-programming stuff.鈥�
arXiv
