World record for the entanglement of twisted light quanta

Nov 02, 2012
False-color image of a laser beam exhibiting a superposition of 100 right-handed and 100 left-handed quanta of orbital angular momenta, resulting in 100+100=200 bright spots on the inner ring. Credit: Robert Fickler/University of Vienna

(—The Vienna research team led by Anton Zeilinger has achieved a new milestone in the history of quantum physics: The scientists were able to generate and measure the entanglement of the largest quantum numbers to date. To this end, the researchers developed a new method for entangling single photons which gyrate in opposite directions. This result is a first step towards entangling and twisting even macroscopic, spatially separated objects in two different directions. The researchers at the Vienna Center for Quantum Science and Technology (VCQ), situated at the University of Vienna, and the Institute for Quantum Optics and Quantum Information (IQOQI) at the Austrian Academy of Sciences have were able to get their pioneering results published in the current issue of the renowned scientific journal Science.

is usually considered to be the theory of extremely lightweight objects, such as atoms or photons, or of exceptionally small units, namely very small quantum numbers. One of the most fascinating phenomena of quantum physics is that of entanglement. Entangled quanta of light behave as if able to influence each other – even as they are spatially separated. The question of whether or not entanglement is limited to tiny objects or very small quantum numbers came up already in the early days of quantum physics. Now, the Vienna group has taken the first step for testing quantum mechanical entanglement with rotating photons. To illustrate, a quantum mechanical figure skater would have the uncanny ability to pirouette both clockwise and counter-clockwise simultaneously. Moreover, the direction of her rotations would be correlated with the twirls of another, entangled, skater – even if the two ice dancers whirl far removed from each other, in ice rinks on different continents. The faster the two quantum skaters pirouette, the larger is the quantum number of their rotation direction, the so-called . "In our experiment, we entangled the largest quantum numbers of any kind of particle ever measured," declares Zeilinger with a wry smile.

Long-exposure photo of laser light in "donut modes" (light beams with no intensity in the middle). Credit: Robert Fickler/University of Vienna

Could quantum ice dancers exist in reality?

It has been common knowledge for about 20 years now that theoretically, there is no upper limit for the angular momentum of photons. Previous experiments, however, have been limited, due to physical restrictions, to very weak angular momentum and small quantum numbers. In the Vienna experiment, it is theoretically possible to create entanglement regardless of the strength of the angular momentum or the scale of its quantum number. "Only our limited technical means stop us from creating entanglement with twisted photons that could be sensed even with bare hands," states Robert Fickler, the main author of the current "Science" publication. And so, the researchers have demonstrated that it is possible in principle to twirl entangled ice skaters simultaneously both in clockwise and counter-clockwise directions. In practice, a number of major challenges need to be addressed before such an experiment can be realized with macroscopic objects.

From fundamental research to technical applications

In addition to the fundamental issue of the limits of macroscopic entanglement, the physicists address possibilities of potential applications. They are, for example, able to use the created photons for very precise angular measurements already at low intensities of light. This feature is of advantage in particular when investigating light sensitive materials, as for example some biological substances. "The special features of provide the fantastic possibility to perform such measurements from arbitrary distances and without any contact whatsoever with the measured object, or even at a point in time that lies in the future!" Fickler explains.

Explore further: Physicists design quantum switches which can be activated by single photons

More information: Fickler, R. Quantum Entanglement of High Angular Momenta. Science, Nov. 2, 2012.

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4 / 5 (2) Nov 02, 2012
Would a quantum computer be able to run a reality simulation to the detail level necessary to simulate as if the object is real? Crosses into the topics of are we ourselves living in a simulation and is the future of humanity to expand out into the galaxy or be seduced into solely inhabiting realities of our own creation over which we have full control.

I for one might hard pressed to reject the yummy steak dinner of "The Matrix" ;-)
not rated yet Nov 02, 2012
not rated yet Nov 02, 2012
The point of this research is, the orbital angular momentum is not quantized with compare to spin or polarization of photons - it's classical physics trait of these otherwise quantized objects. So you can introduce an arbitrary amount of energy into single photon in this way. The heavily coupled photons will behave like tiny magnets, who could get entangled with their orbital angular momentum to arbitrary high temperatures like the magnetic domains in iron or nickel and they could be entangled even with microscopical objects. Note that the entangled photons resemble the electron orbitals of Rydberg states of atoms, which do behave semiclassically too. The strong coupling of photons with high angular momentum could explain the stability of ball lightning too.
1 / 5 (1) Nov 04, 2012
… One of the most fascinating phenomena of quantum physics is that of entanglement. Entangled quanta of light behave as if able to influence each other – even as they are spatially separated…

It is interesting to note that even we have gain some useful things from modern physics such as quanta of light, but something such as - entanglement is look like a magic! The reason behind is that modern physics theories are lack of their physical models to explain the working mechanism. Understanding their physical mechanism (below) may turn the magic to reality.

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