Unbreakable quantum entanglement

May 10, 2017, University of Vienna
The rotating centrifuge in which the entangled photon source was accelerated to 30 times its weight. Credit: IQOQI/ÖAW

Einstein's "spooky action at a distance" persists even at high accelerations, researchers of the Austrian Academy of Sciences and the University of Vienna were able to show in a new experiment. A source of entangled photon pairs was exposed to massive stress: The photons' entanglement survived the drop in a fall tower as well as 30 times the Earth's gravitational acceleration in a centrifuge. This was reported in the most recent issue of Nature Communications. The experiment helps deepen our understanding of quantum mechanics and at the same time gives valuable results for quantum experiments in space.

Einstein's theory of relativity and the theory of are two important pillars of modern physics. On the way of achieving a "Theory of Everything," these two theories have to be unified. This has not been achieved as of today, since phenomena of both theories can hardly be observed simultaneously. A typical example of a mechanical phenomenon is entanglement: This means that the measurement of one of a pair of light particles, so-called photons, defines the state of the other particle immediately, regardless of their separation. High accelerations on the other hand can best be described by the of relativity. Now for the first time, quantum technologies enable us to observe these phenomena at once: The stability of quantum mechanical entanglement of can be tested while the photons undergo relativistically relevant acceleration.

Quantum entanglement proves to be highly robust

Researchers of the Viennese Institute of Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences (OeAW) and of the University of Vienna have now investigated this area of research experimentally for the first time. They could show in their experiment that entanglement between photons survives even when the source of including the detectors are experiencing free fall or are being accelerated with 30g, that is, 30 times the Earth's acceleration. Doing so, the Viennese researchers have experimentally established an upper bound below which there is no degradation of entanglement quality.

The frame in the fall tower at the Institute of Automotive Engineering of the TU Dresden with the quantum-optical design. Credit: IQOQI/ÖAW
Important for quantum experiments with satellites

"These experiments shall help to unify the theories of quantum mechanics and relativity," says Rupert Ursin, group leader at IQOQI Vienna. The sturdiness of quantum entanglement even for strongly accelerated systems is crucial also for quantum experiments in space. "If entanglement were too fragile, quantum experiments could not be carried out on a satellite or an accelerated spacecraft or only in a very limited range," exemplifies Matthias Fink, first author of the publication.

In this tower the experiments of the Viennese quantum physicists were carried out in weightlessness. Credit: IQOQI/ÖAW
12 meters falling height and 30g

In order to prove the robustness of , quantum physicist Matthias Fink and his colleagues mounted a source of polarization-entangled pairs in a crate which was firstly dropped from a height of 12 meters to achieve zero gravity during the fall. In the second part of the experiment, the crate was fixed to the arm of a centrifuge and then accelerated up to 30g. As a comparison for the reader: A roller coaster ride exerts maximally 6g on the passengers.

Detectors mounted on the crate monitored the photons' entanglement during the experiments. Analysing the data, the physicists could calculate an upper bound of disadvantageous effects of acceleration on entanglement. The data showed that quality did not significantly exceed the expected contribution of background noise. "Our next challenge will be to stabilize the setup even more in order for it to withstand much higher accelerations. This would enhance the explanatory power of the experiment even further," says Matthias Fink.

First author Matthias Fink in the quantum laboratory at the Institute for Quantum Optics and Quantum Information at the Austrian Academy of Sciences. Credit: ÖAW/Klaus Pichler

Explore further: Researchers demonstrated violation of Bell's inequality on frequency-bin entangled photon pairs

More information: Experimental test of photonic entanglement in accelerated reference frames, Nature Communications, 2017. DOI: 10.1038/NCOMMS15304

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1 / 5 (1) May 10, 2017
It's way past time for sci-writers to stop gushing, "Spooky action, blah, blah". No one not living on Mars is not sick of this tired put-down of entanglement, not unlike the despised `god particle' moniker of the Higgs. AE did not believe in god or spooks, & used those terms colloquially. But now the sci-writers, lacking any creativity for modern descriptions, all parrot AE.
not rated yet May 10, 2017
"The rotating centrifuge in which the entangled photon source was accelerated to 30 times its weight"

What? Is this supposed to mean the centrifuge produced 30g?
5 / 5 (1) May 10, 2017
The use of intriguing and interesting language to inspire interest in the subject at hand is a tool used by all journalists. Spooky action at a distance has been referred to as often as it has because it is effective at gaining attention. To lobby for the removal of such an iconic phrase as spooky action at a distance from scientific journals would be counterproductive to the goal of spreading interest in the scientific study of reality and the laws governing it. There is an intrinsic value to use outrageous language to describe outrageous scientific phenomenon. One of Einstein's greatest contributions to science was the interest he created in the subject. Also while his religious beliefs were far from firmly established he often referred to a Force having a role in the guiding of our universe. The article was informative, interesting, and entertaining. And just to make clear what was very clear in the article, yes 30 times Earth's gravity is 30g. It said 30g multiple times
not rated yet May 10, 2017
The force does not guide. It survives. Whether anyone learns... we'll see.
5 / 5 (2) May 10, 2017
"What? Is this supposed to mean the centrifuge produced 30g?"

Fill a bucket on a rope with water, whirl it around, figure out why the water doesn't spill.
Or read this :)
not rated yet May 11, 2017
What was discovered was that the aperatus could survive. The limited "relative forces" of these experiments really can't be expected to do much else. Want to determin the "strength" of entangment then send one of the entangled pairs through an accelerator.
not rated yet May 11, 2017
I know that it is frustrating but it is a "pop science" site, Read peer reviewed paper for science.

Hence you have here peddling cliches, catch phrases, gross simplifications in the aura of mystery and discovery while scientific formalism suffers. All in attempt to draw audiences to science and advertisers.

This particular piece fails to explain what actually those researchers wanted to accomplish and why would they expect entanglement of photons (a phase entanglement vs. spin (magnetic) entanglement) to be affected by inertial acceleration of measly 30g (1E5g may be).

Also and most importantly why would they expect to influence an "undetermined" state of a phase of light of entangled pair by mechanical force. I am sure in the paper they answer those questions quite simply.

An interesting take on addressing the problem of misinterpretation of QM I found here:
Da Schneib
1 / 5 (1) May 11, 2017
It's an important point that entanglement still occurs across varying gravity strengths. It's one of those assumptions that must be tested; these are some important negative results.
not rated yet May 13, 2017
Silly monkeys playing semantics with their stone age knives and bearskins
1 / 5 (1) May 13, 2017
Please be aware that Einstein's relativity theory has already been disproved both logically and experimentally (see "Challenge to the special theory of relativity", March 1, 2016).

The most obvious and indisputable experimental evidence, which everybody with basic knowledge of special relativity should immediately understand: is the existence of the absolute time shown by the universally synchronized clocks on the GPS satellites which move at high velocities relative to each other while special relativity claims that time is relative (i.e. the time on each reference frame is different) and can never be synchronized on clocks moving with relative velocities.

Therefore, there is no need to unify quantum mechanics and relativity.
not rated yet May 13, 2017
This "spooky" action is most likely based on perfectly real wormhole. That is actually not an hole but particles are just connected OUTSIDE of space.
not rated yet May 13, 2017
Time is not coordinate, it is just speed of light. Local parameter for each particle. This is even weaker then relative time. But I cannot see who that harms synchronization if clocks move in known way.
May 13, 2017
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not rated yet Jun 20, 2017
Perhaps I have this wrong-please correct me!
The universe at the beginning was incredibly small and compact.It the expanded to a very large size.If quantum entanglement exists as described all the particles that existed at the formation of the universe must have been densely compact and entangled.They then moved away from each other but must still remain entangled no matter how far away.Particles must exist at the opposite end of the universe that are still entangled with their original partner particles.Therefore these particles must be able to communicate with each other faster than the speed of light or instantaneouly.If this is correct communication over vast distances would be possible.

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