Quantum Entanglement Experiment Shows How Future Can Affect Past In Quantum World

Scientists have entangled particles in such a way that a future decision can affect the past states of the particles.

By: Clara Moskowitz, LiveScience Senior Writer
Published: 04/30/2012 11:30 AM EDT on LiveScience

Spooky quantum entanglement just got spookier.

Entanglement is a weird state where two particles remain intimately connected, even when separated over vast distances, like two die that must always show the same numbers when rolled. For the first time, scientists have entangled particles after they've been measured and may no longer even exist.

If that sounds baffling, even the researchers agree it's a bit "radical," in a paper reporting the experiment published online April 22 in the journal Nature Physics.

"Whether these two particles are entangled or separable has been decided after they have been measured," write the researchers, led by Xiao-song Ma of the Institute for Quantum Optics and Quantum Information at the University of Vienna.

Essentially, the scientists showed that future actions may influence past events, at least when it comes to the messy, mind-bending world of quantum physics.

In the quantum world, things behave differently than they do in the real, macroscopic world we can see and touch around us. In fact, when quantum entanglement was first predicted by the theory of quantum mechanics, Albert Einstein expressed his distaste for the idea, calling it "spooky action at a distance."

The researchers, taking entanglement a step further than ever before, started with two sets of light particles, called photons. [Stunning Photos of the Very Small]

The basic setup goes like this:

Both pairs of photons are entangled, so that the two particles in the first set are entangled with each other, and the two particles in the second set are entangled with each other. Then, one photon from each pair is sent to a person named Victor. Of the two particles that are left behind, one goes to Bob, and the other goes to Alice.

But now, Victor has control over Alice and Bob's particles. If he decides to entangle the two photons he has, then Alice and Bob's photons, each entangled with one of Victor's, also become entangled with each other. And Victor can choose to take this action at any time, even after Bob and Alice may have measured, changed or destroyed their photons.

"The fantastic new thing is that this decision to entangle two photons can be done at a much later time," said research co-author Anton Zeilinger, also of the University of Vienna. "They may no longer exist."

Such an experiment had first been predicted by physicist Asher Peres in 2000, but had not been realized until now.

"The way you entangle them is to send them onto a half-silvered mirror," Zeilinger told LiveScience. "It reflects half of the photons, and transmits half. If you send two photons, one to the right and one to the left, then each of the two photons have forgotten where they come from. They lose their identities and become entangled."

Zeilinger said the technique could one day be used to communicate between superfast quantum computers, which rely on entanglement to store information. Such a machine has not yet been created, but experiments like this are a step toward that goal, the researchers say.

"The idea is to create two particle pairs, send one to one computer, the other to another," Zeilinger said. "Then if these two photons are entangled, the computers could use them to exchange information."

You can follow LiveScience senior writer Clara Moskowitz on Twitter @ClaraMoskowitz. For more science news, follow LiveScience on twitter @livescience.

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Comments

[Inannawhimsey]

04:15 PM on 06/07/2013

data leads where the data leads, no matter what we think or feel :3 awe-some! john wheeler's 'participatory universe', here we go! ;3

[storiesfromhavendotcom]

03:42 PM on 05/05/2012

The quantum level of matter is so difficult to understand-- I am glad we have scientists and mathematicians who can comprehend this field and bring real world benefits from such a strange realm.

[butterfly218]

04:56 PM on 05/05/2012

This man , Andrew Basiago says we already have . You can read his story here on HP . HP is a leader on these stories and we thank them .

[mangez merde]

01:35 AM on 05/04/2012

Slightly off-topic but:

This question was used in a study of intuitive thinking versus analytical thinking.

A bat and ball cost $1.10.

The bat cost $1.00 more than the ball.

How much did the ball cost. ????

[NunyaBus99]

10:13 AM on 05/04/2012

5 cents

[NunyaBus99]

10:15 AM on 05/04/2012

Since it is 1 dollar MORE (more being the key word) that would make the bat 1.05. So 1.05+ .05 cents = 1.10

[mangez merde]

01:33 AM on 05/04/2012

If Suzy bakes a pie and cuts it into 8 pieces, and gives Victor 3 pieces, how many pieces do Bob and Alice control ???

Zero.

O'K. I think I've got it.

[Newthron]

09:46 PM on 05/03/2012

Isn't it the confirmation of the double spin, the particle existing in two states, like 0 and 1, left right, with the observer affecting its behavior, almost as if he sees what he expect to see or want to see. Mind over matter.

Man, I have many questions now.
This experiment was conduct with photons, light particles, could it be done with neutrinos, matter?
If yes and the experiment conducted with photon particles which has shown that the instantaneous behavior is true, are we close to say that there is in the quantum world a particle that is probably able to go from tangible to intangible without losing energy, and evolving beyond the speed of light?
Am I getting confused there?

[mdonaldwil]

05:31 PM on 05/03/2012

This way I can make a move in the "game"; see its possible effect, and if its not right; take it back and make a different move! Bah HA HA! And the evidence disappears.

[White Raven]

06:06 AM on 05/03/2012

My question is: Within entangled pairs, how quickly is information communicated? Is it truly instantaneous, therefore circumventing the speed of light? Would it provide a method of faster-than-light communication over cosmic distances?

[BLinCincinnati]

11:52 AM on 05/03/2012

From what I understand yes. I read an article a while back that proposed this very thing... using entangled pairs to transmit information across distances. They proposed that eventually we could send a device like this with future space explorers so that they could communicate with Earth in real time and not the long delays between transmissions. The thing the article didn't get into that made me wonder... if you have one of these devices on a ship travelling near the speed of light, and the other on Earth, due to relativity time would pass slower on the ship than on Earth, so would you even be able to communicate while moving? But for communication between non-moving objects like settlements on a distant planet, it would theoretically work.

[White Raven]

12:01 PM on 05/03/2012

I'm guessing that since everything is in relative motion to everything else in some form that there's no reason you couldn't communicate while moving. As to what sort of effects that would have upon the nature or timing of the communications, I couldn't really say.

[MorpheusXNYC]

04:18 AM on 05/04/2012

Yes, communication between entangled pairs is FTL, hence the tremendous interest in this field.

This same technology exists in science fiction as the "ansible" in the Hainish cycle series of books ("The Left Hand of Darkness, etc) and the "Ender's Game" series of books as well as going by the name "lodestone resonator" in the His Dark Materials (The Golden Compass) series.

It's a fascinating bit of quantum madness along with the wave function, quantum foam, the other 9 dimensions (beyond the first 3 we know), how space and time are one fabric and all these other total headscratchers that blow your mind.

I LOVE science. :-)

[seanrm92]

12:54 AM on 05/03/2012

dfghfitugyojhlhklj,m hjlk24w3restuxfgp98yiulkj

Sorry, just wiping bits of my brain off of my keyboard after my head exploded. Seriously though, this stuff is fascinating.

[Chris Eakin]

11:35 PM on 05/03/2012

Exactly !

[CPAwADD]

04:40 PM on 05/02/2012

Time- a stubbornly persistent illusion. Albert Einstein

[-swift]

01:03 PM on 05/02/2012

I asked my wife for quantum entanglement last night. She said, "Let's not, and say we did."

It was fantastic.

[kareemachan]

02:19 PM on 05/02/2012

LOL!

[Jim NLN]

08:46 AM on 05/02/2012

This might help explain the weird entanglement the Tea Party has on the Republican Party. Even now we see past statements of Dear Leader (Mitt Romney) strangely reverse themselves.

[crankyCrackPot]

10:59 AM on 05/02/2012

Republicans don't believe in Science. ;-)

[Matthew West]

05:40 AM on 05/02/2012

This is how subspace communications worked for gene roddenberry.....

[crankyCrackPot]

11:00 AM on 05/02/2012

The quantum leap and quantum entanglements are proof that in the world of the really small, information can travel faster than light.

[PTerrys]

06:19 PM on 05/02/2012

Or rather that information does not need to be transmitted at all.

[MorpheusXNYC]

04:20 AM on 05/04/2012

What will blow your mind is when you find out that information can actually be sent back in time and that actions in the present can change the states of matter in the past.

Quantum physics is a hell of a thing...

[Varys]

02:55 AM on 05/02/2012

I'm curious, why couldn't this be used for faster-than-light communication? Keep Alice and Bob's photons on Earth, while you send Victor's to a distant planet. Upon arrival, Victor decides whether to entangle the photon; the information is now transferred as a "1" if Alice and Bob's photons are entangled, or a "0" if they are not.

My assumption is that this will not work, but why not?

[PatrickBoucher]

12:38 PM on 05/02/2012

I hesitate to comment because it is very easy to get lost in these scenarios.

But I think part of the answer is in the results of the experiment as reported. The way out of these paradoxes always requires a careful examination of the actual measurements that need to be performed. In the usual case of attempting to send information through measurement of entangled particles (say between Charles and David), it is possible for Charles to measure his photon, resulting in a constraint on David's subsequent measurements, but no way for David to discriminate from his set of measurements whether Charles has measured his photon. That is, the measurement by David, while constrained, does not contain information from Charles without knowing the result of Charles's measurement, which must be transmitted to David subluminally.

Things are more complicated in your scenario, but the experiment shows that Alice and Bob's photons can become entangled by Victor before or after Alice and Bob perform their measurements. I suspect there if one looks at all possible measurements performed on Alice and Bob's photons, they probabilistically produce a set of results in which there is no way to discriminate between sets produced when Victor has or has not entangled his photons in the absence of some additional, subluminally transmitted, information from Victor about his measurements.

(In the grand tradition of Fermat, let me claim that I have a wonderful proof that unfortunately cannot be contained in the word limit here.)

[Varys]

01:23 PM on 05/02/2012

I think what you're saying makes sense. Basically, we would have no way of knowing if Alice and Bob's photons were entangled by Victor unless we receive information about Victor's measurement subluminally. I wouldn't be surprised if this is the actual explanation.

[Bogstomper2]

01:15 AM on 05/02/2012

"...have entangled particles after they've been measured and may no longer even exist."

I can wrap my head around the idea of two particles being quantumly entangled. I can picture real-world analogies for that, like a pair of gears that remain synchronized even after they're separated. But this post-existence entanglement baffles me. How do you synchronize gears, or entangle particles, that no longer exist?

I need more schooling...

[JVene]

11:12 AM on 05/04/2012

As best I understand at the moment...

It hints that time isn't what we think it is. From the perspective of these particles it may be that time doesn't "happen" as we view it to happen.

Previous entanglement experiments hint that even though the particles are separated in 3D space, they're not separated from each other outside 3D space (that may not be the genuine meaning, but that's metaphorically what it looks like).

This experiment now suggests that even separation in time is irrelevant from the particle's perspective. From our viewpoint they are now separated in time, but from their perspective they are not.

[mamacat]

12:17 AM on 05/02/2012

It seems that many things are impossible, until they are not.

By proclamation, the Sun went around the Earth, until finally it did not.

It was impossible for people to fly, until they did.

The world was flat, until it was round.

And the list goes on, and on.

Science is a wonderful thing.