Daily Archives: January 23, 2017

Physicists show that real-time error correction in quantum communications is possible

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Now researchers have shown that there is a grey area where Nature cannot tell the difference between the classical and the quantum. This opens the possibility of first performing quantum experiments with a type of classical light called “classically entangled” light.

By preparing and sending a so-called “classically entangled” beam the team could show that this was identical to sending a quantum state. This means that the observed quantum entanglement decay due to noise in the link can be reversed, paving the way for major advances in secure quantum links in fibre and free-space.

“We showed for the first time that classical light can be used to analyse a quantum link, acting as a direct equivalent to the behavior of the quantum state,” says Bienvenu Ndagano, lead author and PhD student at Wits University.

“Not similar, or mimicking, but equivalent. To show this, we exploited a particular type of laser beam, called vector beams, that have the property of being non-separable and sometimes called ‘classically entangled’.”

Ndagano explains that the quintessential property of quantum entanglement is the non-separability of the state, meaning that one part of the system cannot be separated from the other. “But non-separability is not unique to the quantum world: you can find it in weather maps where the locations on the map and the temperatures at those locations can’t be separated.”

More intriguingly, classical vector beams have this property too, which the team calls “classically entangled” light.

Says Forbes, “What we asked was: does this mean that classical light can be used in quantum systems – a grey area between the two worlds that we call classical entanglement?”.

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This work allows for long distance quantum links to be established and tested with classically entangled light: as there is no shortage of photons in the classical light, all the measurements needed to fix the errors in the quantum state can be done in real-time without destroying the quantum information.

Thus, real-time error correction is possible as you can run experiments in the classical world that will tell you how to fix the error in the quantum world.

Source: Physicists show that real-time error correction in quantum communications is possible

Your Android device’s Pattern Lock can be cracked within five attempts

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New research from Lancaster University, Northwest University in China, and the University of Bath, which benefitted from funding from the Engineering and Physical Sciences Research Council (EPSRC), shows for the first time that attackers can crack Pattern Lock reliably within five attempts by using video and computer vision algorithm software.

By covertly videoing the owner drawing their Pattern Lock shape to unlock their device, while enjoying a coffee in a busy café for example, the attacker, who is pretending to play with their phone, can then use software to quickly track the owner’s fingertip movements relative to the position of the device. Within seconds the algorithm produces a small number of candidate patterns to access the Android phone or tablet.

The attack works even without the video footage being able to see any of the on-screen content, and regardless of the size of the screen. Results are accurate on video recorded on a mobile phone from up to two and a half metres away – and so attacks are more covert than shoulder-surfing. It also works reliably with footage recorded on a digital SLR camera at distances up to nine metres away.

Researchers evaluated the attack using 120 unique patterns collected from independent users. They were able to crack more than 95 per cent of patterns within five attempts.

Complex patterns, which use more lines between dots, are used by many to make it harder for observers to replicate. However, researchers found that these complex shapes were easier to crack because they help the fingertip algorithm to narrow down the possible options.

During tests, researchers were able to crack all but one of the patterns categorised as complex within the first attempt. They were able to successfully crack 87.5 per cent of median complex patterns and 60 per cent of simple patterns with the first attempt.

Source: Your Android device’s Pattern Lock can be cracked within five attempts