When the first quantum computers are realised, they will be room-sized, super-cooled and incredibly expensive. Most of the organisations wanting to utilise the unique capabilities of these machines won’t have one of their own sitting in the server room.
Initially then, businesses will likely purchase runtime on quantum computers, and interact with it remotely over the internet.
Given the sensitive and confidential nature of the data and programs businesses will want to run on quantum computers – the issue of security is already rearing its head.
Until recently, it was thought to be impossible to maintain private interactions with quantum computers, unless the user had their own quantum network.
But in a paper published this month in Physical Review X, researchers from RMIT University, National University of Singapore and Singapore University of Technology and Design have presented a “tantalising possibility that it may be possible for a classical user to hide a computation from a quantum server”.
Spinning blind
Users wanting to perform computations on a remote quantum computer are faced with two main security concerns that need to be overcome, the researchers say.
“The privacy concern is that the description of their computation, both the program and any input data, remains hidden even from the server. The correctness concern is that a malicious server might tamper with their computation, sending them a misleading result; hence, ideally such behaviour would be detectable,” RMIT’s Dr Nicolas Menicucci et al write in their paper Flow Ambiguity: A Path Towards Classically Driven Blind Quantum Computation.
What’s needed are ‘blind quantum computing protocols’. While these have been proposed in previous research, until now they have required that at least two parties possess quantum capabilities.
“Removing this requirement and allowing a purely classical user to interact with a single quantum server would greatly expand the practicality of delegated quantum computation,” the researchers say.
The protocol suggested by the paper’s authors “exploits the ambiguity” in the flow of information in a measurement-based quantum computer.
The method means quantum computer can't tell which qubits were used for inputs, which for operations and which for outputs. The sheer number of possible sequences also protects from any reverse engineering attempts.
The result “allows the tantalising possibility that it may be possible for a classical user to hide a computation from a quantum server”.
A secure Qloud
A number of vendors have already announced their intention to deliver quantum computing remotely.
IBM made its own five qubit quantum computer available to research institutions via the cloud in May last year. The company said its commercial 'Q' quantum computing program will deliver paid quantum computing consulting and services to users sometime this year.
In a Nature editorial in March, researchers at Google’s Quantum AI Laboratory said the company planned to support research by “offering access to Google's quantum processors through cloud services”. The article was entitled: 'Commercialise quantum technologies in five years'.
Last month, Telstra’s chief scientist Hugh Bradlow (who will be departing from the telco in October), told Computerworld the company too hoped to one day provide 'quantum-as-a-service'.
Telstra is a key investor in the Centre for Quantum Computation and Communication Technology (CQC2T) at the University of New South Wales, announcing at the end of 2015 it would be funding the centre with $10 million over five years.
"[There are] a whole lot of applications of quantum computers which our customers are going to want to use...[they] will need a lot of hand holding and they are not going to run the equipment themselves because it's complicated, it requires dilution fridges and all the equipment," Bradlow said.
Just as cloud providers work hard to maintain their clients' privacy and security, those offering quantum services commercially will need to do the same.
The protocols suggested by researchers this week are a big step towards this reality.
“While we do not offer a full solution,” the paper states, “the results support the possibility of making secure cloud quantum computing accessible to a wider population using existing communications infrastructure.”