Simultaneously Measuring Entangled Particles

[audioloop]

I've also heard a suggestion that the "first" measurement may send a backwards in time to when the entangled particles were first produced, ensuring that the spins are always opposite.

This seems to solve the issue about the ordering of the measurements, and removes a bit of the "spookiness" involved with the particles being spatially separated.
I'm not sure what other issues this might create though. And I can't think of an experiment which could for this.

Interesting though ...

retrocausality from the
Two State Vector Formalism.

Time Symmetric . . it through the Forum. In some threads you will to very interesting papers. It preserves locality but ruins causality.
I really like not only the preservation of locality but also causality aside because it makes you think as time being much more similar to space than what one usually does (in this the arrow of time problem sort of does not occur in microscopic world and arises in the macroscopic human world -by the way my thought about it is that it is a human illusion which arises as a consequence of the fact that we, human beings, are consumers of ordered energy and producers of entropy, and, because of this, we order our life from situation of low entropy -past- to situations of high entropy -future--)

Ps: Remember that all that I said is just an which probably will never be tested! (Nevertheless I have that someone much more intelligent than me will do it!)

Physical Review A 79, 052110
Multiple-time states and multiple-time measurements in quantum mechanics
Yakir Aharonov, Sandu Popescu, Jeff Tollaksen, and Lev Vaidman

... Finally we discuss the implications of our approach to quantum mechanics for the problem of the flow of time...

There is no movement(and hence no causality) in spacetime, according to GR.

the block universe, recently i opened a thread about, but it was deleted.

If you could construct a closed timelike curve where entropy always increases and Novikov's Self Consistency Principle is satisfied I don't see any problem with this.

from CTCs

Perfect State Distinguishability and Computational Speedups with Postselected Closed Timelike Curves
Foundations of Physics March 2012, Volume 42, Issue 3, pp 341-361

...an entangled state efectively creates a noiseless quantum channel into the past...

 

[audioloop]

and there are Timlike Entanglement , i.e. entanglements in time.Physical Review A 85, 012306 (2012)
...entangled between timelike separated regions of spacetime...
...non-separability across time...----
and an experiment proposed:

Physical Review Letters 109, 033602 (2012)
...We propose a realistic circuit QED experiment to test the extraction of past-future vacuum entanglement to a pair of superconducting qubits...
...We show that this experiment can be realized with current technology and discuss its utility as a possible implementation of a quantum memory...

i have the complete papers if somebody wish it.

 

[mfb]

i have the complete papers if somebody wish it.

arXiv has them, too:

Extraction of timelike entanglement from the quantum vacuum (your link there seems broken)
Extracting past-future vacuum correlations using circuit QED

 

[audioloop]

arXiv has them, too:

Extraction of timelike entanglement from the vacuum (your link there seems broken)
Extracting past- vacuum correlations using circuit QED

yes, i know, but... mod`s do not like to much, that forums users put arxiv papers.
you know...

 

[mfb]

They are just different links to the same thing - the publications were accepted (and therefore passed peer review), so they shouldn't be completely crap.

References that appear only on http://www.arxiv.org/ (which is not peer-reviewed) are subject to review by the Mentors. We recognize that in some fields this is the accepted means of professional communication, but in other fields we prefer to wait until formal publication elsewhere.

I did not highlight "only", this is already done in the rules.

 

[audioloop]

I've also heard a suggestion that the "first" measurement may send a signal backwards in time to when the entangled particles were first produced, ensuring that the spins are always opposite.

This seems to solve the issue about the ordering of the , and removes a bit of the "spookiness" involved with the particles being spatially separated.
I'm not sure what other issues this might create though. And I can't think of an which could test for this.

Interesting though ...

The Conference...

http://www.chapman.edu/research-and-institutions/quantum-studies/speakers-schedule.aspx

Aharonov, Hartle, Gross, Unruh, Pearle, Leggett, Turok, Gisin, Carroll, Vaidman, Steinberg......!


talks on video

.

 

[myshadow]

No. In every frame, there is a description which does not involve any propagation backwards in time. And all frames give the same measurements.

Could you please elaborate? From one reference point, A collapses the system and as a result B has a defined spin. From another reference point, the measurement of B seems to happen first and collapses the system. As a result, A takes a defined spin. I don't see how the instantaneous action does not violate causality. I'm probably misunderstanding something.

As a side question, has it been proven empirically (somehow) that the spins are actually undefined before measurement? I'm guessing this is impossible. btw, I'm an engineer not a physicist so I'm sorry if the answers are obvious. Thanks.

 

[mfb]

Could you please elaborate? From one reference point, A collapses the system and as a result B has a defined spin. From another reference point, the measurement of B seems to happen first and collapses the system. As a result, A takes a defined spin.

Both reference frames have their own time-order of the events - you cannot transmit information with those measurements, so you do not need a unique ordering of those events.

As a side question, has it been proven empirically (somehow) that the spins are actually undefined before measurement? I'm guessing this is impossible. btw, I'm an engineer not a physicist so I'm sorry if the answers are obvious. Thanks.

Look up Bell's theorem. It has, and it is a very interesting experiment.