Quantum Transportation Leaps Forward

Livia Gershon | 07 September, 2012 | Science

Einstein called the notion of entangled quantum particles “spooky action at a distance.” Now, some scientists call it a way to build a more secure, faster internet.

The latest advance in the field comes from European researchers, who have published the results of a May experiment in which they “transported” quantum particles 88 miles between two Canary Islands. “Transported” goes in quotes here because what moved from one island to another wasn’t actually a subatomic particle. Instead, they moved the particle’s characteristics, essentially turning a distant bit of matter into an exact copy of the local one.

The experiment marks the longest distance ever traversed with this kind of technology. The previous record, a bit over 60 miles, was set earlier this year by Chinese scientists.

The European team said their work required a number of technical innovations. Where past experiments have used optical fiber, the distance involved here would have resulted in too much degradation of the signal. Instead, they used lasers.

For all the science fiction nerds out there, the research may bring to mind the ansible, first envisioned by Ursula Le Guin, which lets far-flung worlds communicate instantaneously. Sadly, that’s not on the horizon yet. Because of the mind-boggling characteristics of quantum particles, it’s essentially impossible for someone on the receiving end of a quantum communications device to understand the information being sent without an additional, slower-than-light message that allows for translation.

Nonetheless, the scientists say the technology is developing to the point where it may have practical uses before long. The next step is extending the communication distance to allow messages from Earth to a satellite, or from satellite to satellite. Although the distances involved in that kind of experiment would be much larger, the signal would be able to move more freely in space because there’s less atmosphere to plow through.

Getting that kind of communication functioning could create the basis for a worldwide “quantum internet.” One of the big advantages over the old-fashioned internet would be that, because quantum particles can’t be observed without being changed, any attempt at hacking messages would be instantly obvious. The technology could also lead to faster data analysis with “quantum computers.”

Image credit: IQOQI/Vienna

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Current research poses serious questioning about the relevance of Gershon’s statement:

‘One of the big advantages over the old-fashioned internet would be that, because quantum particles can’t be observed without being changed, any attempt at hacking messages would be instantly obvious.’

Scientists cast doubt on renowned uncertainty principleSeptember 7, 2012′The findings build on recent challenges to Heisenberg’s principle by scientists the world over. Nagoya University physicist Masanao Ozawa suggested in 2003 that Heisenberg’s uncertainty principle does not apply to measurement, but could only suggest an indirect way to confirm his predictions. A validation of the sort he proposed was carried out last year by Yuji Hasegawa’s group at the Vienna University of Technology. In 2010, Griffith University scientists Austin Lund and Howard Wiseman showed that weak measurements could be used to characterize the process of measuring a quantum system. However, there were still hurdles to clear as their idea effectively required a small quantum computer, which is difficult to build.”In the past, we have worked experimentally both on implementing weak measurements, and using a technique called ‘cluster state quantum computing’ to simplify building quantum computers. The combination of these two ideas led to the realization that there was a way to implement Lund and Wiseman’s ideas in the lab,” says Rozema. It is often assumed that Heisenberg’s uncertainty principle applies to both the intrinsic uncertainty that a quantum system must possess, as well as to measurements. These results show that this is not the case and demonstrate the degree of precision that can be achieved with weak-measurement techniques. “The results force us to adjust our view of exactly what limits quantum mechanics places on measurement,” says Rozema. “These limits are important to fundamental quantum mechanics and also central in developing ‘quantum cryptography’ technology, which relies on the uncertainty principle to guarantee that any eavesdropper would be detected due to the disturbance caused by her measurements.” “The quantum world is still full of uncertainty, but at least our attempts to look at it don’t have to add as much uncertainty as we used to think!” More information: The findings are reported in the paper “Violation of Heisenberg’s Measurement-Disturbance Relationship by Weak Measurements”. prl.aps.org/abstract/PRL/v109/i10/e100404 Journal reference: Physical Review Letters Provided by University of TorontoRead more at: http://phys.org/news/2012-09-scientists-renowned-uncertainty-principle.html