Breakthrough may herald secure home quantum computing

Scientists at Oxford University Physics have made a major breakthrough in the development of quantum security that could one day pave the way for people to unleash the true power of quantum computing safely and securely, including, potentially, in the home.

The so-called blind quantum computing approach was developed and tested in the UK by a team led by Oxford University Physics postdoctoral research assistant Peter Drmota, using a trapped-ion quantum processor.

Ion-trapping – in which charged atomic particles or ions are confined using electromagnetic fields – is one of several proposed approaches to large-scale quantum computing, and Drmota is among a number of scientists who believe ion-trapping holds the most promising potential means of “doing” quantum computing.

Speaking to Computer Weekly ahead of the publication of the team’s results this week, he said that thanks to the experiments conducted at Oxford, the concept may be starting to pull ahead of the field.

“We are the first ones to combine quantum computing with quantum cryptography in a scalable way,” said Drmota, who describes quantum computing as being as far from classical computing as classical computing is from an abacus.

The commercial potential is already known to be immense, with quantum computing expected to have applications in fields that will help humanity solve some of the biggest challenges of the next 100 years, from drug discovery, to fighting new viruses, to developing mitigations for climate breakdown.

“But to release the potential, we need to make sure the data that people or companies want to process is safe, and this is where blind quantum computing comes in, as it hides not only the data, but also the algorithm that is used to process the data from the server, and from any eavesdroppers along the way,” explained Drmota.

Few scientific theories have been tested to a greater degree of scientific precision than quantum mechanics, and the blind approach relies on the established fact that quantum objects cannot be copied or observed without changing their state.

What that means is if the quantum object encodes the data, nobody can copy or read it without corrupting it, and any interference can be noticed – indeed, any interference will destroy the data.

“That fundamentally protects both the data and the computation,” said Drmota. “This is why it’s called blind quantum computing, because the quantum computer is blind to the data it is processing.

“Nobody will be able to spy on the data because it effectively looks random to them. It looks random to anybody except the client. This is the beauty of the approach. And the randomness here is due to us using the most advanced encryption – that is the one-time pad, which is the most secure way of performing encryption. The client can use this encryption scheme for perfect security.”

In the experiments, Drmota and his team created a system that comprised an ordinary fibre network link that connected a quantum computing server and a simple device set up to detect light particles, or photons, at an independent client computer that remotely accessed the server – via the cloud, essentially. Using a unique combination of quantum memory and photons, they were then able to successfully test the approach by remotely performing a number of computations using the sample data on the server, without the server seeing any of the data at any point.

“Using blind quantum computing, clients can access remote quantum computers to process confidential data with secret algorithms, and even verify the results are correct, without revealing any useful information,” said Drmota.

The verification of the results of the data processing is an aspect of blind quantum computing that Drmota finds particularly interesting.

“If we have a really powerful quantum computer and we’re solving a problem that we couldn’t solve otherwise, how are we going to check that the solution is correct, because we have no other means of solving the problem? Here, the blind quantum computing aspect comes to the rescue, because we can now test the quantum computer without the quantum computer knowing,” he explained.

By alternating actual computation with tests that the quantum computer cannot tell apart sufficiently often, the data processor can increase their confidence in the computations being correct, in addition to being secure.

“Realising this concept is a big step forward in both quantum computing and keeping our information safe online,” he added.

It is the relative simplicity of the blind quantum computing method that appears to hold great promise for the future. The approach pioneered at Oxford appears to be scalable, and the researchers anticipate that future realisations could encompass networks of cloud-hosted quantum servers and distributed clients, with photons routed using optical switches.

The quantum servers will, of course, be as complex as they have to be, but everything else is on the shelves today: the client computers are classical, ordinary computers; photon detectors are relatively cheap; and fibre networks are everywhere.

In summary, said the team, the research paves the way for secure delegation of confidential quantum computations from a minimally resourced client to a fully capable yet untrusted quantum server, bringing the power of quantum computing safely to an ordinary endpoint. The era of quantum computing and the era of the hybrid workforce could be about to collide.

The research was supported by funding from the UK Quantum Computing and Simulation (QCS) Hub and scientists from the National Quantum Computing Centre, Paris-Sorbonne University, the University of Edinburgh and the University of Maryland in the US. The full study is published in the journal Physical Review Letters.