Bell violation with extra particles

[edguy99]

Taken from an earlier thread:

"If the two devices are aligned in matching orientations (in opposite directions to allow for the initial state), then QM says that 100% of the results should match. If either of the two devices is turned at 90 degrees to the original orientation, then QM says that the average correlation should be zero, so 50% of the results should match and 50% should be different. If either device is turned to 45 degrees from the original orientation, then the classical projection of one direction on the other is cos 45 degrees, which is about 0.7 (70%), so to get this correlation we need 85% of results to be the same and 15% to be different."

Wrt to the style of measurement shown http://www.upscale.utoronto.ca/PVB/Harrison/SternGerlach/SternGerlach.html" the spinning sphere can model the up and down motion but fails the Bell test to predict the correct percent of same or different spin orientations that two observers see.

One problem with the classical model is the measurement of spin at exactly 90 degrees. Should the particle go up or down? One way to resolve this is: any particle measured that is within 12.5 degrees of 90 degrees to the measuring device, will not go up or down but will start to tumble in the magnetic field with loss of momentum. These particles do not make it to the detector.

So we setup the experiment with Bob and Alice offset by 45 degrees:

This setup does meet the test of the observed 15% difference, but does anyone know if these devices end up with extra particles in them and if there is any kind of relationship between the spin offset and/or the extra particles left behind?

 

[DrChinese]

... One problem with the classical model is the measurement of spin at exactly 90 degrees. Should the particle go up or down? One way to resolve this is: any particle measured that is within 12.5 degrees of 90 degrees to the measuring device, will not go up or down but will start to tumble in the magnetic field with loss of momentum. These particles do not make it to the detector.

...

I think you are trying to say that not all particles are detected, and that the missing particles account for the difference between a classical model of spin and the quantum model. Or?

I am trying to narrow down what you are hypothesizing.

 

[edguy99]

I think you are trying to say that not all particles are detected, and that the missing particles account for the difference between a classical model of spin and the quantum model. Or?

I am trying to narrow down what you are hypothesizing.

Basically yes. In this model of a spin 1/2 particle, all particles do not reach the detector, specifically particles that are close to 90 degrees to the measuring device (or their motion is so disrupted by the tumbling that their spin direction would have to be considered random even if they happen to hit the detector).

 

[DrChinese]

Basically yes. In this model of a spin 1/2 particle, all particles do not reach the detector, specifically particles that are close to 90 degrees to the measuring device (or their motion is so disrupted by the tumbling that their spin direction would have to be considered random even if they happen to hit the detector).

Well, there is no such observed effects as tumbling or momentum loss due to spin. Further, the experiment is rotationally invariant. You will see 100% matching regardless of how you orient the SG apparatus - 0, 45, 90 degrees, no matter, same result. The effects you hypothesize would be easily seen in basic experiments, and they just don't happen.

Further, all of this is supported by experiments with many different kinds of particles, including light. In addition, there have been tests in which 100% of all pairs are detected and they show the same result.

 

[edguy99]

.. In addition, there have been tests in which 100% of all pairs are detected and they show the same result.

Thanks, appreciate a link on this.

 

[DrChinese]

Thanks, appreciate a link on this.

Sure:

http://www.nature.com/nature/journal/v409/n6822/full/409791a0.html

"Here we have measured correlations in the classical properties of massive entangled particles (9Be+ ions): these correlations violate a form of Bell's inequality. Our measured value of the appropriate Bell's ‘signal’ is 2.25 ± 0.03, whereas a value of 2 is the maximum allowed by local realistic theories of nature. In contrast to previous measurements with massive particles, this violation of Bell's inequality was obtained by use of a complete set of measurements. Moreover, the high detection efficiency of our apparatus eliminates the so-called ‘detection’ loophole."