Monday 26 October 2015

Using the first loophole-free experiment physicists demonstrate the spookiness of Quantum theory 

Quantum theory's 'spooky action at a distance' has now been confirmed officially with new loophole-free experiment.

It has been proved by physicists that particles behave in some weird ways, in the sense that though they are separated by distance they can still influence each other.
Quantum theory's 'spooky action at a distance' has now been confirmed officially with new loophole-free experiment.

Earlier this year, physicists explained that according to "Quantum Entanglement" two particles which are light years away can still influence each other; for instance if one particle is poked then another particle which is placed at a distance of light year can also respond to this poking without any messages being passed through the space. This sort of 'intimate connection' between the particles is termed as "Entanglement" by "quantum physics".This law of 'Quantum Entanglement' defies Einstein's "law of relativity" - according to which no particle can travel faster than speed of light. Thus, Einstein termed this intimate connection in between the separated particles as "spooky action at a distance" and he believed the spookiness of quantum theory to be totally weird.

Many papers have proved the existence of quantum entanglement; however, physicists at Netherlands have posted a new research paper online on August 24 to the arXiv.The paper titled "Experimental loophole-free violation of a Bell inequality using entangled electrons spins separated by 1.3 km" describes the first loophole free experiment with which physicists actually succeeded in meeting the mathematical gold standard for proving entanglement- a goal that was set down some fifty years ago.

Currently, the paper has to go undergo a review from other physicists and it is being reviewed at a scientific journal but it has already drawn attention in the community of quantum physics.

"It’s a shame that Einstein didn’t live long enough to learn about this," say Christoph Simon, a theoretical quantum physicist at the University of Calgary in Alberta, Canada. "The universe is not as reasonable as he wanted it to be."

First loophole free Quantum experiment to prove the "Quantum spookiness"

Physicists from Netherlands, UK and Spain entangled pairs of electrons which were separated by a distance of 1.3 km. This first loophole free quantum experiment was led by B. Hensen, researcher from Delft University of Technology, Netherlands. During the experiment, the research team measured one of the electrons and simultaneously another group closely watched its partner to check if was affected.

It was in 1960s when an Irish physicist John Bell conducted an experiment get some clear explanation for this quantum entanglement. The experiment is known as 'Bell experiment' and it has always showed that quantum entanglement theory is real. Practically speaking, most of the physicists believe that the correlation between the particles should cease completely as the particles move far away from each other; however quantum theory defies this belief and proves that the particles continue communicating with each other and is not affected by distance.

Physicists have been repeatedly conducting the Bell experiment for almost 3 decades and it has always proved the quantum theory to be real.

If the quantum theory and quantum entanglement was already proved then why are physicists conducting it again and again? Well, this question might arise in most of our minds!

Now, here comes the real hitch, physicists believe that the Bell experiment has a 'lot of loopholes'.

In the Bell experiment, physicists used 'entangle photons', photons are super-fast in nature and hence it is very hard to pin them down and measure. So literally speaking 80 percent of the photons were usually lost even before they were measured thus leading to vague results.
Physicists then started using 'entangled ions' instead of 'entangled photons' just to close the loophole and to derive some clear conclusions. Using the entangled ions presented some other complications and in fact it opened another loophole! It is a fact that you cannot keep ions apart from each other for a long time and by default some information does pass between the entangled particles, which could be at a rate less than that of the light's speed.

Thus, this new loophole free experiment is very much important. Physicists claim they have finally managed to close both the loopholes as they have combined the benefits of photons with that of the electrons thus ensuring that they can be measured.

The research team conducted the experiment by entangling the spin of two electrons with that of two different photons. Initially, the two electrons were located in different laboratories which were separated by a distance of 1.3 km and the photons were sent to some third location. Then these were separately entangled with each other.

A writer at science report, FQXi Blogs writes: "As soon as the photons are entangled, BINGO, so too are the two original electron spins, seated in vastly distant labs. The team carried out 245 trials of the experiment, comparing entangled electrons, and report that Bell’s bound is violated."

So far, scientists used to blame the loopholes  in the Bell experiment for proving the quantum theory; however a loophole free experiment also proved the existence of quantum entanglement proving "spooky" quantum behavior definitely exists.

For now the early results of this new research has been posted at the arXiv, and authors write: "Our experiment realizes the first Bell test that simultaneously addresses both the detection loophole and the locality loophole." The experiment is now being screened for publication in a science journal for peer review.

While speaking to Jacob Aron over at New Scientist, Anton Zeilinger, leader of a rival team at the University of Vienna, Austria and not a part of the research team told: "It’s a very nice and beautiful experiment, and one can only congratulate the group for that. I expect they have improved the experiment, and by the time it is published they’ll have better data ... There is no doubt it will with stand scrutiny."

Quantum Cryptography: 

One of the other goals as to why physicists have been constantly working on conducting a "loophole-free" Bell experiment is because this will be a huge step in the direction of 'Quantum cryptography'.

Quantum Cryptography: Chris Monroe, an experimental quantum physicists at the Joint Quantum Institute in Maryland says that the a loophole-free Bell test can be used for a new kind of communications network or we can say 'quantum version' of the internet.
When entangled particles are sent over internet it would be protected against hackers and even eavesdropper will not be able to tap any information, further if anyone tries to even eavesdrop it will not go unnoticed.

"The security of the information is guaranteed by the fundamental laws of physics," says Monroe.

According to the report by Devin Powell at Popular Science, Dutch scientists, Hensen et al at the Delft University of Technology used two diamond chips for conducting this loophole free experiment.

Powell writes: "Whether such un-hackable internet networks, if ever developed, will need to be made of diamond remains to be seen. During its nine-day run, Hensen’s glittering contraption popped out a mere 245 pairs of entangled particles. A commercially viable system would need to spit out thousands or more a minute.With only 245 events, statistics dictates a four percent chance that the result was due to chance, meaning that Bell’s threshold may not have actually been crossed."

On the contrary, Paul Kwiat, an an experimental quantum physicist who works with photons and is also in the race at the University of Illinois at Urbana-Champaign says: "In other words, there’s a 96 percent chance that they won the race. The nail’s not very deep in the coffin, and I’m certain that before long there will be results that have a much lower statistical uncertainty."

Well, it goes without saying that such an un-hackable internet is the need of the hour, in today's world where internet plays a very important and literally has become part and parcel of everyone's lives. Thus it seems Hensen et al has finally nailed the issue of hacking and at the same time proved the existence of Quantum spookiness with a loophole-free experiment.
After this week's buzz regarding Stephen Hawking's black hole theory, it is the turn of "Quantum spookiness" to be in the spotlight and seek attention from all the lovers of physics.

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