QIT: quantum hope or quantum hype?

Quantum information technology (QIT) is here already. Judging by the impressive turn out at the Cambridge-MIT Institute's recent Industry in the Quantum Age chinwag session at the Royal Society, it's here to stay.

Also clear, though, is that despite repeated forecasts that we're on the precipice of a revolutionary base jump, even the basics of QIT are poorly understood outside the research community. The research community aren't necessarily always the best people to turn science into real-world applications, either, so the questions remain: will it change the world, and if so, when and how?

FundaMental

A quantum is the smallest unit energy can be divided into. So for light, that's a photon, and thanks to Einstein, we know mass and energy are interchangeable, so a quantum can also be a particle like an atom or an electron carrying energy.

QIT is the party where physics meets computer science. Applications take advantage of the Addams family of freaky effects that come in to play on the quantum scale.

As it continues to pack more and more transistors onto silicon, traditional digital technology will have to deal with quantum effects soon (see the interconnect bottleneck here), but the game for the old guard will be how to dodge them, not embrace their potential.

The science of secrecy

Quantum cryptography exploits Heisenberg's uncertainty principle to make for unbreakable security. It states properties of quanta are mutually inaccessible to an observer. Most commonly so far in quantum cryptography, the polarisation direction of a photon has been used.

The principle is at the heart of the conundrum posed by quantum properties and means that just by breaking into a quantum encrypted key exchange and determining the direction, a hacker is instantly detectable, and anything they get from the communication is worthless. The polarisation direction the photon is emitted in is random; a hacker would have to guess which direction to measure it in, is bound to make mistakes, and because of uncertainty, affects all subsequent quanta.

Quantum cryptography is already here, of course. It's high-end stuff, and MagiQ, which makes and sells a box to do it, says most of its customers are exploring the possibilites, like US telco Verizon, or too hush-hush to talk about. Former MI6 chief Sir Richard Dearlove was at the Industry in the Quantum Age workshop, so its pretty clear the sort of government agencies that have an interest.

Current quantum cryptography systems suffer from some limitations. The distance the emitters can send light through optic fibres is an issue, currently at a maximum of around 100km. There's a need for true single photon detectors and emitters to be deployed to supercede current hardware compromises too. Such road humps will be summited in pretty short order if the industry buzz is anything to go by. Along with start-ups like MagiQ, big boys Toshiba, IBM and HP have quantum cryptography specialists beavering away at making the technology more stable and accessible over the next five years. A system that uses quantum cryptography to secure cashpoint transactions is in development.

Spooks aren't just interested in the quantum encoding of information. The flipside is that a quantum computer's theoretical processing grunt could smash their top secret communications channels in no time. Quantum cryptography pioneer Gilles Brassard once said: “If a quantum computer is ever built, much of conventional cryptography will fall apart.”

The party planner's trilemma

A working quantum computer with such practical applications is further away, but the experts reckon the implications are profound enough that the IT industry should start educating itself today.

Bob's got a problem. His cellar has three lights in it, and the three switches which operate them are upstairs. Bob needs to know which switch works which light so he can set the perfect mood for an upcoming cheese, wine and gimp evening he'll be having with a few close friends.

“Simple”, he thinks at first; flick one switch, nip downstairs, note which bulb lights up, repeat once and by a process of elimination all three circuit paths are illuminated.

Bob's an idle fetishist however; just the thought of walking up and down the stairs of his suburban faux-Gothic pile twice gives him a bout of angina. After several days of feverish Da Vinci-esque kitchen brainstorming, a whole pack of jumbo chalks and 62 cups of weapons-grade Java, the answer reveals itself.