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January 3, 2012 — Ottawa, Ontario
Faced with the baffling randomness of quantum mechanical theory a half-century ago, Albert Einstein famously argued that God wouldn’t play dice with the universe. Yet in the depths of a building on Sussex Drive in Ottawa, a team of NRC physicists is now rolling “cosmic dice” fast and furiously.
Firing a very rapidly pulsing high-intensity laser through a thin pane of diamond about a millimetre square, their experimental equipment detects “quantum mechanical fluctuations” — random movements and flashes of light at the molecular level —from the diamond’s carbon lattice, to generate truly random numbers.
Quantum measurements have often been difficult and costly exercises, carried out by viewing microscopic systems chilled to near absolute zero. The NRC device, working at room temperature on a slice of diamond visible to a naked eye, detects quantum fluctuations by amplifying them to a level that can be measured using typical — and inexpensive — photodiodes.
“Quantum mechanics is mind-boggling. But we use its uncertainty in the random number generator,” says Dr. Ben Sussman of NRC. “You take this diamond, you shine this light through it in the right way, and you measure the light that comes out. And at room temperature, just a small cylinder maybe a millimetre long is in a totally quantum mechanical state. It can’t be described classically.”
How it works: A laser pulse is focused into a diamond, generating a signal with a random phase. After filtering out background noise, the signal is combined with a reference pulse at a beamsplitter. A small lateral tilt is introduced and the signal is compared with the reference using a sensor array.
Comparing the emerging light with the incoming light yields the long strings of random numbers that can be used to lock and unlock electronic communications and data.
Huge quantities of random numbers are a basic need for the very serious encryption schemes that businesses, banks, governments and the military use to protect their most sensitive data.
The random number generator, which was developed at NRC in collaboration with Professor Ian Walmsley at the University of Oxford, promises rapid, uncrackable encryption for high-speed information exchanges — such as military transmissions, secure banking, or online purchasing — that underpin the modern connected world. In addition to encrypting data communications, the device likely holds benefits for ultra-high-performance computing, and for making gaming platforms and multimillion dollar lotteries more trustworthy.
Each intense pulse of a 100 picosecond (1 picosecond = 0.000000000001 seconds) laser in the NRC random number generator places the interior of a diamond in a momentary quantum state that cannot be described by classical physics. During each pulse, that state is different, in a completely unpredictable way.
“It fully utilizes the uncertainty of quantum mechanics for security applications. The laser light can scatter off any of the atoms. And because it can scatter off any of them, in quantum mechanics it scatters off all of them — but you don’t know which one,” says Dr. Ben Sussman. “Quantum mechanics is only 100 years old, so we have a lot to learn. We’re just starting to think of developing technologies that take advantage of its crazy properties, like ‘superposition’, ‘uncertainty’, ‘coherence’ and ‘entanglement’.”
Until recently, these numbers — called “quasi-random numbers” — have usually been produced using complex mathematical formulas yielding long strings of numbers that only appear to be random. But like a standard pair of six-faced gaming dice, the formulas are subject to certain rules. If the conditions of the physical throw — or the base algorithm — can be recreated exactly, the rules dictate that the result has to be exactly the same.
The famous Enigma cipher machine that the German military used for secret messages in the 1940s was a case in point. It could generate so many millions of encryption variations that it was thought to be impenetrable, but its sequences weren’t truly random. Allied codebreakers could, and did, reproduce them to break the codes.
True random numbers, generated very quickly, inundate potential eavesdroppers so heavily that they can’t decrypt a signal. Typical encryption for online banking right now is considered strong at 128 or 256 bits, says team member Dr. Philip Bustard. Fully developed, the diamond device will have much higher encryption, and generate numbers at terahertz rates, a thousand times faster than the gigahertz speeds of processors in current desktop computers. And because the device can run at room temperature on ordinary-sized components, it has the potential to very quickly affect new technology. “I think that Canadians will want to be leaders in these future technologies, which will have serious implications as the world becomes more and more interconnected,” says Dr. Sussman. “All of a sudden we’re building technology that relies on crazy quantum mechanics. Quantum strangeness is inexplicable, yet we can really use it as a resource.”