Quantum computing techniques could be used to bring complete security to the cloud, says an international team of scientists.
They've carried out a demonstration of quantum computation in which the input, data processing and output remain unknown to the quantum computer.
Like many really ground-breaking technologies, it's likely that quantum computing will be extremely expensive, at least at first.
The team envisages a future where users outsource their comutations to specilized facilities, in much the same way as they do now with supercomputers. Data privacy is likely to be crucual.
"Quantum physics solves one of the key challenges in distributed computing. It can preserve data privacy when users interact with remote computing centers," says Stefanie Barz, lead author of the study, which appears in Science.
Using the team's technique, the quantum server performs calculations, but has no way of finding out what it's doing.
The demonstration uses photons to encode the data. The user prepares qubits – the fundamental units of quantum computers – in a state known only to himself, and sends these qubits to the quantum computer. The quantum computer entangles the qubits according to a standard scheme.
The actual computation is measurement-based, with the processing of quantum information implemented by simple measurements on qubits. The user tailors measurement instructions to the particular state of each qubit and sends them to the quantum server.
Finally, the results of the computation are sent back to the user, who can interpret and utilize them. Even if the quantum computer or an eavesdropper tries to read the qubits, they gain no useful information, without knowing the initial state; they are 'blind'.
For the technique to become commonplace, though, there would need to be some easy way for users to create the qubits in the first place.