Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. 24/7 Space News .




TIME AND SPACE
Photons run out of loopholes
by Staff Writers
Vienna, Austria (SPX) Apr 17, 2013


Lab IQOQI, Vienna 2012. Image courtesy Jacqueline Godany.

A team led by the Austrian physicist Anton Zeilinger has now carried out an experiment with photons, in which they have closed an important loophole. The researchers have thus provided the most complete experimental proof that the quantum world is in conflict with our everyday experience. The results of this study appear this week in the renowned journal Nature (Advance Online Publication/AOP).

When we observe an object, we make a number of intuitive assumptions, among them that the unique properties of the object have been determined prior to the observation and that these properties are independent of the state of other, distant objects. In everyday life, these assumptions are fully justified, but things are different at the quantum level.

In the past 30 years, a number of experiments have shown that the behaviour of quantum particles - such as atoms, electrons or photons - can be in conflict with our basic intuition.

However, these experiments have never delivered definite answers. Each previous experiment has left open the possibility, at least in principle, that the observed particles 'exploited' a weakness of the experimental setup.

Quantum physics is an exquisitely precise tool for understanding the world around us at a very fundamental level. At the same time, it is a basis for modern technology: semiconductors (and therefore computers), lasers, MRI scanners, and numerous other devices are based on quantum-physical effects.

However, even after more than a century of intensive research, fundamental aspects of quantum theory are not yet fully understood. On a regular basis, laboratories worldwide report results that seem at odds with our everyday intuition but that can be explained within the framework of quantum theory.

On the trail of the quantum entanglement mystery
The physicists in Vienna report not a new effect, but a deep investigation into one of the most fundamental phenomena of quantum physics, known as 'entanglement.'

The effect of quantum entanglement is amazing: when measuring a quantum object that has an entangled partner, the state of the one particle depends on measurements performed on the partner.

Quantum theory describes entanglement as independent of any physical separation between the particles. That is, entanglement should also be observed when the two particles are sufficiently far apart from each other that, even in principle, no information can be exchanged between them (the speed of communication is fundamentally limited by the speed of light). Testing such predictions regarding the correlations between entangled quantum particles is, however, a major experimental challenge.

Towards a definitive answer
The young academics in Anton Zeilinger's group including Marissa Giustina, Alexandra Mech, Rupert Ursin, Sven Ramelow and Bernhard Wittmann, in an international collaboration with the National Institute of Standards and Technology/NIST (USA), the Physikalisch-Technische Bundesanstalt (Germany), and the Max-Planck-Institute of Quantum Optics (Germany), have now achieved an important step towards delivering definitive experimental evidence that quantum particles can indeed do things that classical physics does not allow them to do.

For their experiment, the team built one of the best sources for entangled photon pairs worldwide and employed highly efficient photon detectors designed by experts at NIST.

These technological advances together with a suitable measurement protocol enabled the researchers to detect entangled photons with unprecedented efficiency. In a nutshell: "Our photons can no longer duck out of being measured," says Zeilinger.

This kind of tight monitoring is important as it closes an important loophole. In previous experiments on photons, there has always been the possibility that although the measured photons do violate the laws of classical physics, such non-classical behaviour would not have been observed if all photons involved in the experiment could have been measured.

In the new experiment, this loophole is now closed. "Perhaps the greatest weakness of photons as a platform for quantum experiments is their vulnerability to loss - but we have just demonstrated that this weakness need not be prohibitive," explains Marissa Giustina, lead author of the paper.

Now one last step
Although the new experiment makes photons the first quantum particles for which, in several separate experiments, every possible loophole has been closed, the grand finale is yet to come, namely, a single experiment in which the photons are deprived of all possibilities of displaying their counterintuitive behaviour through means of classical physics.

Such an experiment would also be of fundamental significance for an important practical application: 'quantum cryptography,' which relies on quantum mechanical principles and is considered to be absolutely secure against eavesdropping. Eavesdropping is still theoretically possible, however, as long as there are loopholes. Only when all of these are closed is a completely secure exchange of messages possible.

An experiment without any loopholes, says Zeilinger, "is a big challenge, which attracts groups worldwide." These experiments are not limited to photons, but also involve atoms, electrons, and other systems that display quantum mechanical behaviour. The experiment of the Austrian physicists highlights the photons' potential.

Thanks to these latest advances, the photon is running out of places to hide, and quantum physicists are closer than ever to conclusive experimental proof that quantum physics defies our intuition and everyday experience to the degree suggested by research of the past decades.

Bell violation with entangled photons, free of the fair-sampling assumption: Marissa Giustina, Alexandra Mech, Sven Ramelow, Bernhard Wittmann, Johannes Kofler, Jorn Beyer, Adriana Lita, Brice Calkins, Thomas Gerrits, Sae Woo Nam, Rupert Ursin, Anton Zeilinger. In: Nature (Advance Online Publication/AOP). April 14, 2013. DOI: 10.1038/nature12012

.


Related Links
University of Vienna
Understanding Time and Space






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





TIME AND SPACE
On wings of light
Munich, Germany (SPX) Apr 06, 2013
LMU physicists have, for the first time, successfully transmitted a secure quantum code through the atmosphere from an aircraft to a ground station. Can worldwide communication ever be fully secure? Quantum physicists believe they can provide secret keys using quantum cryptography via satellite. Unlike communication based on classical bits, quantum cryptography employs the quantum states o ... read more


TIME AND SPACE
Characterizing The Lunar Radiation Environment

Russia rekindles Moon exploration program, intends setting up first human outposts there

Pre-existing mineralogy may survive lunar impacts

Lunar cycle determines hunting behaviour of nocturnal gulls

TIME AND SPACE
Accurate pointing by Curiosity

NASA Mars Orbiter Images May Show 1971 Soviet Lander

Opportunity is in position for solar conjunction at 'Cape York' on the rim of Endeavour Crater

NASA spacecraft may have spotted pieces of Soviet spacecraft on Mars

TIME AND SPACE
Testing Spacesuits in Antarctica, part 1

Obama's budget would boost science, health

Underwater for outer space

NASA Celebrates Four Decades of Plucky Pioneer 11

TIME AND SPACE
Shenzhou's Shadow Crew

Shenzhou 10 sent to launch site

China's Next Women Astronauts

Shenzhou 10 - Next Stop: Jiuquan

TIME AND SPACE
UH Engineering Researcher's Theories to be Tested Aboard ISS

Unmanned Russian space freighter leaves space station toward fiery end

Europe sets June 5 for launch of space freighter

Spooky action at a distance aboard the ISS

TIME AND SPACE
ILS Proton Launches Anik G1 for Telesat

Ukraine aims to accelerate space industry development

Payload integration is underway for Vega's second mission from the Spaceport

Ecuador to launch first homemade satellite

TIME AND SPACE
Can One Buy the Right to Name a Planet?

Retired Star Found With Planets And Debris Disc

The Great Exoplanet Debate

NASA Selects Explorer Investigations for Formulation

TIME AND SPACE
For the very first time, two spacecraft will fly in formation with millimeter precision

High pressure gold nanocrystal structure revealed

Scientists design new adaptive material inspired by tears

UC Research Demonstrates Why Going Green Is Good Chemistry




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement