English
09.03.2012

Ultra-secure Quantum Computing Explained

Futurezone.at recently sat down with PhD candidate Stefanie Barz of Vienna’s Quantum Science and Technology department to explain her groundbreaking “blind computation” procedure.

Earlier this year, the University of Vienna’s Quantum Science and Technology department published their findings regarding a highly secure blind computation process that combines the power of quantum computing and quantum cryptography. In addition to being the world’s first demonstration of this theory, the team notes that this process can one day have huge implications on internet security, particularly in the growing field of quantum cloud computing.

And while this experiment is remarkable in it’s own right, I’m not really sure how many people outside the realm of quantum physicists, truly understand what and how this experiment has a real world application. To this end, I recently sat down with Stefanie Barz, team lead on the experiment to try to put things into a real world perspective.

They use laser beams
To begin, Stefanie provided me with an exclusive view of the quantum computer used to perform the experiment, including the laser array (Yes, they use laser beams!) used to produce the photons that will eventually be used to carry the data. To be clear, this laser array is a component used to produce the necessary photons that are then sent to the quantum computer. She explained that this array is responsible for entangling photons, meaning that they are in a certain state whereby they share a complex connection to each other. Researchers then measure one state of the photon, thus changing the state of said photon and affecting the state of the second photon. Physicists refer to this connection as super correlation, with Einstein referring to the process as “spooky action at a distance,” or “spukhafte Fernwirkung”. It’s precisely this interaction between particles that makes quantum computing far more efficient from the classical process we’re all familiar with. By capitalizing on the ability of quantum particles to be in more than one state at the same time, this allows the computer to perform any number of possible solutions to a given problem simultaneously.

From green to red
To create these entangled photons, Stefanie and her team use the laser beam to convert the wavelength from green to red, and then on to a blue beam. From this blue beam, the entangled photons are then routed through optical fibers and sent to the quantum computer to be further processed into a cluster state. The cluster state is then used to create the “blind qubit” that will then go on to be measured by the quantum computer.

Granted, that might seem like a whole lot of work (and power – did I mention lasers?) just to create few photons, and thus qubits, but keep in mind that we’re not talking about sending a typical email here. What Stefanie and her team have done is create an absolutely secure form of data processing that cannot be intercepted and understood. In addition to the ultra-secure method of transmission and encryption, the end computer is also unable to detect what it is actually processing.

Now before you start clamoring for your very own quantum computer to send completely secure emails, keep in mind that these devices are still in their infancy. A practical, real-world quantum computer is still far off, as the one I viewed consumed an entire room, and performed only a simple, yet highly effective computation.

Expensive & rare
If and when quantum computers do reach a practical level, it’s a fair statement to make that they’ll be quite expensive, and very rare. Enter cloud computing. With the usage of cloud computing growing on a daily rate, instead of needing their own quantum computer, researchers, (evil?) scientists, and others from around the world could theoretically rent or purchase computational time on said devices. Obviously, if you’re in need of the services of a quantum computer, there’s a good chance that you’d really rather not have others knowing exactly what you’re working on. Thus the need for the blind computation, and absolutely secure data processing.

Quantum computers do contain entangled qubits, therefor; simply generating and sending qubits isn’t going to solve this security issue fully. What Stefanie and her team have done is add an additional layer of security to this already confounding method of data transfer.

The random code
The trick here is a series of what appears to be random bits of code, but is in fact pre-encrypted by the sender. This “random” series of data is a form of photon polarization (vertical or horizontal), and remains encrypted throughout the calculation, and is still able to be processed by the quantum computer (although the computer has no idea what it is processing). However, if an eavesdropper where to intercept the data anywhere along the transmission path, they would have no way of knowing exactly how to put the encryption (polarization sequence) together to make any sense of the data. Having created the original encryption, the end receiver can then interpret the results, resulting in an absolutely secure form of data processing.

Two quantum algorithms in test
In the demonstration conducted at the University of Vienna, Barz and her team tested two quantum algorithms; Deutsch’s, which detects certain regularities in mathematical functions, and Grovers’, which can search an unsorted database (think phone book). They created the above-mentioned “spooky action at a distance” state of photons, and encrypted their data transmission. Having received the photons and created an entangled cluster state, the quantum computer then carried on and began solving the problem. However, because of this extra layer of polarized encryption, there was no way to determine exactly what the computer was doing and/or processing, thus proving the security of their test. The team had to wait until the results were returned to discover if the entire process had actually worked.

It’s also worth noting that this level of security is a two-way street. Meaning, those that are responsible for, or even own, a quantum computer are most likely quite protective of their asset. By providing this blind computational process, the sender of the data would have no way of peering into the inner workings of the computer processing their request, and of course, vice versa.

Who needs a quantum computer?
You and I are probably not going to have any need for a quantum computer in the near future, nor will we be sending data that could cause unrest in certain parts of the world, (sorry, pr0n doesn’t count). With that said, while Stefanie denies any contact, I can’t help but wondering if any government or military organizations have been in touch, as this is the absolute perfect application for such computational power and data transmission. Yes, the blind computational demonstration is a slightly-over-the-top form of secrecy, but in today’s world, there’s a perfect German expression, “Sicher ist Sicher.” (Better safe than sorry).

PhD candidate Stefanie Barz of Vienna’s Quantum Science and Technology department