Quantum cryptography offers best solution to internet security

Information stored as photons cannot be infiltrated due to uncertainty principle

Fans of Breaking Bad may inadvertently know more about quantum mechanics than they think. Walter White is a quantum character. As one fans' website put it, he is "dweeb and master criminal, loving father and ruthless killer, inept buffoon and calculating manipulator, particle and wave, all at the same time".

This is why the show’s writers opted for “Heisenberg” as his drug lord alias, a tip of the hat to theoretical physicist, Werner Heisenberg.

Even the biggest fans of Breaking Bad, or those who simply have a grasp of the basics of quantum mechanics, may struggle to come up with too many practical applications for quantum theory in everyday life.

In fact, quantum physicists are working on an application that, if cracked, would have significant impact on the digital world we live in.


Arguably, the biggest weakness of the global digital communications network is security. Just ask Julian Assange, Edward Snowden or Satoshi Nakamoto (reported pseudonym for the Bitcoin founder). Most confidential information online can be intercepted by any well-trained computer whizz.

Quantum cryptography offers a path to improved internet security, the idea being that you can hide information in the quantum state of sub-atomic particles. "You can write information into the state of a photon – the particles which make up beams of light," explains Paul Eastham, Naughton Assistant Professor at the Trinity School of Physics. "It's like a vessel for information. In a classical computer, it would be known as a bit. In quantum mechanics, it's known as a qubit."

Researchers from Griffith’s Centre for Quantum Dynamics in Brisbane, Australia, have managed to send qubits of information in photons.

"Information needs to be sent securely between two distant parties every day," says Dr Michael Hall, "theory" author of the research recently published by Griffith's Centre for Quantum Dynamics.

“The best way to do that is to have a secure code that they can set up that nobody else would know about. One way is for the two parties to physically meet up and share a random code.

“In the real world, that’s not possible. If you want to buy a product overseas using your credit card details, you will not have met the seller but still need to generate a random, secure code.”

Here comes Walter White again. The Heisenberg uncertainty principle – which states that you cannot know two properties of an object simultaneously (such as the exact position and the exact speed), because all things in the universe act like both particles and waves at the same time – allows for the quantum generation of secure codes that can be sent from one party to the other.

“Any eavesdropper that tries to figure out the answers to your codes’ measurements, cannot do so because they don’t know which property to measure – position or speed,” says Hall. “As the Heisenberg uncertainty principle states, you can’t know both at once, only one or the other.”

The research from Griffith’s Centre for Quantum Dynamics uses the Heisenberg uncertainty principle in a new way: the devices used to generate the codes are “quantum programmed”, by inputting quantum states of light.

This means that it doesn’t matter how insecure a device is. A hacker may be able to hack into the device but they wont be able to reliably determine all properties of the quantum input states. No one can read a quantum programme.

Please do not disturb . . . my photons

Another attractive security aspect of this method of sending information relates to measurement. When you measure a quantum system, you automatically disturb it. Through “quantum steering”, a measurement made on one end’s quantum system changes, or steers, the system held by another.

“The two parties can see that disturbance,” says Hall. “If neither are responsible for this change, they can determine that the information channel isn’t secure.”

This level of information security is at once attractive to military, government, and financial institutions. But like GPS or the internet itself, once perfected it will likely become a widely used technology.

It is still hampered by one major challenge: the distance information can securely travel in a quantum state. “The main difficulty in making it directly applicable right now is the matter of loss over kilometres,” says Hall. “We are only able to send information securely over short distances (50-100km) before the light photons begin to get lost. If you take the example of shining a torch in fog, you only have visibility for a short distance in front of you before the light dissipates and reflects off in different directions.

“Our experiment still works even if we lose up to 70 per cent of the light, but only at short distances,” he says.

“We have secured grant funding so we hope to do better by the end of next year and hopefully set up a more secure system. It is likely to be within the order of 15 years from now before this technology is honed though.”

Quantum computing

One quantum holy grail we won’t need to wait as long for is the quantum computer. In theory, such equipment can process macro-scale, highly-complex problems much faster than a classical computer ever could.

Last week, Canadian quantum computing outfit D-Wave announced they had raised a further $29 million CAD (€20.3 million) in funding from an anonymous donor to go along with the $142 million CAD (€100 million) they had already raised from the likes of Goldman Sachs, BDC Capital and In-Q-Tel.

Two D-Wave quantum computers currently operate – one the company built in cahoots with Lockheed Martin, and the other with Nasa, Google and the US-based Universities Space Research Association. However, scientists are in disagreement over whether the D-Wave prototype truly operates as a quantum computer.

In case you needed more confusion, another anomaly of quantum mechanics is that you cannot “look under the hood” of a quantum computer to see what’s happening because doing so would obstruct the quantum mechanics that allows a particle to be both a “zero” and a “one” at the same time.

For those who don’t know much about quantum mechanics, here are two short, useful videos: The Heisenberg uncertainty principle www.youtube.com/watch?x-yt-ts=1422579428&x-yt-cl=85114404&v=TQKELOE9eY4#t=208. Quantum computers explained www.youtube.com/watch?x-yt-ts=1422579428&x-yt-cl=85114404&v=T2DXrs0OpHU#t=379