Researchers led by the University of Vienna’s Stefanie Barz have demonstrated the possibility of using quantum computing to unconditionally secure cloud computing.
The scientists’ work, written up in the journal Science, essentially demonstrates double-blind cryptography.
It consists of an optical implementation of blind quantum computing, Barz told TechNewsWorld. The researchers used lasers, optical fibers, lenses, crystals, mirrors and polarization analyzers to conduct the demo.
The methodology demonstrated by Barz’s team could be used in “factoring very large numbers into their prime factors, [which is] useful for cracking RSA-type encryption; ordering lists such as a Google search; and quantum simulations,” Andrew Cleland, a physics professor at the University of California in Santa Barbara, told TechNewsWorld.
Looking at Blind Quantum Computing
The idea behind blind quantum computing is that the computer processing data doesn’t know anything about the input, the computation it performs on that input or the resulting output.
In conventional schemes, by contrast, the computations — in this experiment’s case, measurements — are known to the quantum computer, so it knows what algorithm it’s running.
The methodology Barz’s team used has the client preparing qubits “in a state only known to himself, and [tailoring] the measurement instruction to the state of the qubits,” Barz said. “The server does not know the state of the qubits and thus cannot interpret the measurement instructions. The server gets zeroes and ones as outcomes, but cannot interpret the values, whereas the client can.”
In addition to providing greater security, blind quantum computing might help cut costs for law enforcement agencies, which need to store vast amounts of data.
“A number of law enforcement agencies have been researching cloud computing as a way to reduce the costs of maintaining vast quantities of digital evidence, but security has been a major consideration,” Darren Hayes, CIS program chair at Pace University, told TechNewsWorld. “Quantum security may quell their fears.”
Details of the Blind Quantum Computing Demo
The researchers “created photons in a so-called ‘blind’ state and entangled them to a blind cluster state,” Barz said.
The photons were created by pumping a crystal with a blue laser beam. The crystal converted some of the incoming photons to red photons. The process is called “spontaneous parametric down-conversion,” Barz said. The resulting red photons were entangled in polarization because of the setting the researchers used.
The researchers then calculated measurement instructions for the Deutsch-Jozsa and Grover’s algorithms, made the corresponding measurements on the blind cluster state, and checked the outcome.
Deutsch-Jozsa is a deterministic quantum algorithm. Grover’s algorithm is used for searching an unsorted database. It’s probabilistic, meaning it gives the most probable answer. Repeating the algorithm increases the probability of getting the right answer by winnowing down the field of probable answers.
Measure for Measure
In measurement-based quantum computation, you begin with qubits in a given fixed entangled state and apply measurements to designated qubits in sequence, according to Richard Jozsa, one of the authors of the Deutsch-Jozsa algorithm.
The basis of a measurement that’s selected may depend on the results of earlier measurements. The final result is determined from the classical data of all the measurement outcomes.
The researchers used one-way quantum computing, also known as the “cluster model.” In this, the resource, or original, state is destroyed by the measurements.
The Blind Quantum Security Eschaton
Getting blind-based quantum security into the real world “is a highly complex task,” Barz said.
It will take 10 to 20 years to have a lab demonstration of a quantum computer “sufficiently powerful to do useful things,” UC Santa Barbara’s Cleland suggested.
Perhaps we might see results sooner rather than later.
“I was at a briefing a few months ago on this very subject, [and] scientists at HP felt they would have something working out and productized in the next decade,” Rob Enderle, principal analyst at the Enderle Group, told TechNewsWorld.
Quantum computers “can decrypt any non-quantum method near-instantly, in theory, rendering all existing forms of encryption obsolete,” Enderle pointed out. “This will make the concerns surrounding Iran’s nuclear efforts seem trivial by comparison if a [foreign] country gets there first.”
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