To test the effect of gravity on quantum entanglement, we need to go to space

Jun 18, 2014 by Carlos Sabin, The Conversation
Darth Vader’s stormtroopers haven’t figured it out. Credit: rpenalozan, CC BY-NC-SA

There is an up-and-coming set of technologies that uses the strange properties of atomic particles predicted by the theory of quantum mechanics, which is the physics of the very small stuff. This technology promises to bring us computers that are faster than all the machines we have ever produced before put together, as well as communication tools no snooping agency can break into and even the capacity to look into the Earth without digging.

At the heart of these technologies is a strange phenomenon called "quantum entanglement". It says that the properties of an atomic particle depend on the properties of another, distant particle, even if there is no physical connection between them. When the properties of one particle change, the twin particle's properties change too.

Now consider that the properties of the first particle could somehow be programmed. If this is encoded in, say, London then its pair in, say, New York will change properties instantaneously. Decoding those properties will mean the transfer of data from London to New York without the need for wires.

Current communication technologies rely on transmission of data over large distances, including Earth-satellites links. If we want to exploit the quantum advantages, we need to transmit quantum properties in such long length scales. For now, however, such has been shown to be feasible only at a distance of a little more than 100km. For it to be truly useful it needs to be useful between, at least, satellites and the Earth.

But testing quantum mechanics at larger distances is difficult. The problem arises because gets in the way. Albert Einstein's work on gravity has stood the test of time, but it only explains phenomena at large scale, such as planets and stars. It failed at the level of atoms. In short, we don't understand how tiny particles are affected by gravity.

And so far pitting Einstein's theory against hasn't been achieved experimentally. It remains one of the biggest challenges in physics. But there may be a solution in an experiment we recently proposed in the New Journal of Physics.

In our idea, two are prepared in an entangled state in between two different satellites orbiting the Earth. As long as they stay in the same orbit, the entanglement exists. However, at some point the orbit of one of the satellite needs to be changed. This is done by firing engines and accelerating to the new location.

The acceleration needed to change orbit is determined by the gravitational forces acting on the satellite: the more distant the new orbit we want to reach, the larger the time that the engines must be switched on to get the required velocity. This is due to the fact that gravity is more intense if the object is closer to the Earth.

We find that such acceleration – and thus, indirectly, gravity – changes the quality of entanglement between the two particles. If our calculations are right, this could be the first experimental proof that shows that gravity will have indirect effects on . Also, if quantum technology has to be used in space, it is vital that this be taken into consideration.

Explore further: Space-based experiment could test gravity's effects on quantum entanglement

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antialias_physorg
5 / 5 (4) Jun 18, 2014
could somehow be programmed. If this is encoded in, say, London then its pair in, say, New York will change properties instantaneously. Decoding those properties will mean the transfer of data from London to New York without the need for wires

Argh. No. Why, why, why is that mistake made over and over? If you encode you break entanglement. Encoding is a SETTING of a property not a measurement. If you encode stuff on one end of an entagled pair then NOTHING happens at the other end. You just break entanglement.

Why don't people ever look up the difference between information transmission and "action at a distance". Two different critters entirely.

We find that such acceleration – and thus, indirectly, gravity – changes the quality of entanglement between the two particles.

Exactly: Change stuff at one end and you degrade entanglement.
DonGateley
1 / 5 (1) Jun 18, 2014
@antialias_physorg: because they want to believe in the impossible. Nothing more, nothing less.

I wish someone would construct a cogent example of how instantaneous information transfer leads to contradiction. One that could be generally understood so that I could cut it and paste it into all the places I see the claim made.
AmritSorli
1 / 5 (2) Jun 19, 2014
no need to go in the space for that. Gravity has no impact on entanglement.
George_Rajna
Jun 19, 2014
This comment has been removed by a moderator.
George_Rajna
Jun 19, 2014
This comment has been removed by a moderator.
swordsman
1 / 5 (1) Jun 19, 2014
Gravity is entanglement, and we have it right here. Note that "gravity" occurs between any two particles.
feath3r
1 / 5 (1) Jun 19, 2014
I agree with antialias_physorg. It sounds like the author is describing quantum teleportation where the information can be encoded, but not taking into an account of the classical channel associated with it.
Quantum Flux
1 / 5 (2) Jun 24, 2014
Does anyone understand the measurement problem in quantum entanglement? Where if time is a negative in the experiment the potential twin particle knows the information a prior i? How can a potential particle know it's spin before it is determined?
Dr_toad
Jun 24, 2014
This comment has been removed by a moderator.
feath3r
1 / 5 (1) Jun 24, 2014
How can a potential particle know it's spin before it is determined?
Quantum Flux,
I don't see an issue with the particle and the twin particle knowing the information prior (after the present measurement, of course) as long as the measurement is not made prior. As long as it is the present measurement collapsing the wave function of the entangled system, there should not be any inconsistency.
My apologies if I have misunderstood your question.

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