- #1
Pat71
- 22
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Although he is primarily an astrophysicist, Dirac medal-winning Oxford Professor James Binney has taught a Quantum Physics course to second-year students at the university for years. A series of 27 of his lectures for the course is featured on the university's official website. Binney's take on the violation of Bell inequalities and Quantum Physics in general seems unorthodox though. He takes an "instrumentalist" approach which views the Copenhagen Interpretation of quantum theory as a useful epistemological "roadmap" to getting results about an underlying reality that it does not accurately represent. Wavefunction collapse is simply seen as a caricature of measurement that is convenient for calculations but has no relation to a microscopic reality which has many definite physical values and of which non-locality is not a feature.
Binney refuses to admit that the violation of Bell inequalities has important ontological implications.
Here is how he accounts for it:
" Many discussions of the EPR experiment generate needless confusion by supposing that after Alice has measured +1/2 for the component of the electron's spin parallel to a, the spin is aligned with a. The electron has half a unit of angular momentum in each of the x, y and z directions, although the signs of the x and y components are unknown when we know the value of Sz.
Hence the most Alice can know about the orientation of the spin vector is that it lies in a particular hemisphere. Whatever hemisphere Alice determines, she can argue that the positron's spin lies in the opposite hemisphere. So if Alice finds the electron's spin to lie in the northern hemisphere, she concludes that the positron's spin lies in the southern hemisphere. This knowledge excludes only one result from the myriad of possibilities open to Bob: namely he cannot find Sz = +1/2. He is unlikely to find +1/2 if he measures the component of spin along a vector b that lies close to the z axis because the hemisphere associated with this result has a small overlap with the southern hemisphere, but since there is an overlap, the result +1/2 is not excluded.
Contrary to the claims of EPR, the results of Bob's measurement are consistent with the hemisphere containing the positron's spin being fixed at the outset and being unaffected by Alice's measurement."
Binney draws the underwhelming conclusion that
"The experimental demonstration that Bell inequalities are violated establishes that quantum mechanics will not be superseded by a theory in which the spin vector has a definite direction."
He adds that "Macroscopic objects only appear to have well-defined orientations because they are not in states of well-defined spin. That is, the idea that a vector points in a well-defined direction is a classical notion and not applicable to objects such as electrons that do have a definite spin."
This is not an interpretation of the violation of Bell's inequalities about which I have heard much.
Nonlocality is not even entertained as a possibility!
It is hard to find discussions of Binney's view online. I hope someone here can provide a critique of it - many students here in Oxford are being blithely taught that there is nothing important or surprising about these famous experimental results. I doubt that's true!
Looking forward to learning more,
Thanks,
Pat
Binney refuses to admit that the violation of Bell inequalities has important ontological implications.
Here is how he accounts for it:
" Many discussions of the EPR experiment generate needless confusion by supposing that after Alice has measured +1/2 for the component of the electron's spin parallel to a, the spin is aligned with a. The electron has half a unit of angular momentum in each of the x, y and z directions, although the signs of the x and y components are unknown when we know the value of Sz.
Hence the most Alice can know about the orientation of the spin vector is that it lies in a particular hemisphere. Whatever hemisphere Alice determines, she can argue that the positron's spin lies in the opposite hemisphere. So if Alice finds the electron's spin to lie in the northern hemisphere, she concludes that the positron's spin lies in the southern hemisphere. This knowledge excludes only one result from the myriad of possibilities open to Bob: namely he cannot find Sz = +1/2. He is unlikely to find +1/2 if he measures the component of spin along a vector b that lies close to the z axis because the hemisphere associated with this result has a small overlap with the southern hemisphere, but since there is an overlap, the result +1/2 is not excluded.
Contrary to the claims of EPR, the results of Bob's measurement are consistent with the hemisphere containing the positron's spin being fixed at the outset and being unaffected by Alice's measurement."
Binney draws the underwhelming conclusion that
"The experimental demonstration that Bell inequalities are violated establishes that quantum mechanics will not be superseded by a theory in which the spin vector has a definite direction."
He adds that "Macroscopic objects only appear to have well-defined orientations because they are not in states of well-defined spin. That is, the idea that a vector points in a well-defined direction is a classical notion and not applicable to objects such as electrons that do have a definite spin."
This is not an interpretation of the violation of Bell's inequalities about which I have heard much.
Nonlocality is not even entertained as a possibility!
It is hard to find discussions of Binney's view online. I hope someone here can provide a critique of it - many students here in Oxford are being blithely taught that there is nothing important or surprising about these famous experimental results. I doubt that's true!
Looking forward to learning more,
Thanks,
Pat