- #1
sahashmi
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- TL;DR Summary
- Can anti realism really save non locality?
Anton Zeilinger, an experimentalist who proved that QM seems to be non local, doesn’t seem to actually believe in non locality himself. In a conference in Dresden, he stated that if one simply abandons the notion that objects have well defined properties before measurement (i.e. if one doesn’t adopt realism), one does not need to posit any sort of non locality or non local/faster than light influences in quantum entanglement.
Tim Maudlin, a prominent proponent of non locality, responds to him stating, as detailed in the book Spooky Action At A Distance by George Musser,
> “When Zeilinger sat down, Maudlin stood up. “You’ll hear something different in my account of these things,” he began. Zeilinger, he said, was missing Bell’s point. Bell did take down local realism, but that was only the second half of his argument for nonlocality. The first half was Einstein’s original dilemma. By his logic, realism is the fork of the dilemma you’re forced to take if you want to avoid nonlocality. “Einstein did not assume realism,” Maudlin said. “He derived it.” Put simply, Einstein ruled out local antirealism, Bell ruled out local realism, so whether or not physics is realist, it must be nonlocal.
> The beauty of this reasoning, Maudlin said, is that it makes the contentious subject of realism a red herring. As authority, Maudlin cited Bell himself, who bemoaned a tendency to see his work as a verdict on realism and eventually felt compelled to rederive his theorem without ever mentioning the word “realism” or one of its synonyms. It doesn’t matter whether experiments create reality or merely capture it, whether quantum mechanics is the final word in physics or merely the prelude to a deeper theory, or whether reality is composed of particles or something else entirely. Just do the experiment, note the pattern, and ask yourself whether there’s any way to explain it locally. Under the appropriate circumstances, there isn’t. Nonlocality is an empirical fact, full stop, Maudlin said.”
Let’s suppose Zeilinger is right. Before any of the entangled particles are measured, none of their properties exist. But as soon as one of them is measured (say positive spin), must the other particle not be forced to come up as a negative spin? Note that the other particle does not have a defined spin before the first one is measured. So how can this be explained without a non locality, perhaps faster than light, or perhaps even an instantaneous influence?
A common retort to this is that according to relativity, we don’t know which measurement occurs first. But then change my example to a **particular** frame of reference. In that frame, one does occur first. And in that frame, the second particle’s measurement outcome is not constrained until the first one is measured. How is this not some form of causation? Note that if there is superluminal causation, relativity would be false anyways, so it makes no sense to use relativity to rule out superluminal causation (that’s a circular argument)
Let’s assume that the many worlds interpretation or the superdeterminism intepretation is false for the purpose of this question, since I know that gets around these issues
Tim Maudlin, a prominent proponent of non locality, responds to him stating, as detailed in the book Spooky Action At A Distance by George Musser,
> “When Zeilinger sat down, Maudlin stood up. “You’ll hear something different in my account of these things,” he began. Zeilinger, he said, was missing Bell’s point. Bell did take down local realism, but that was only the second half of his argument for nonlocality. The first half was Einstein’s original dilemma. By his logic, realism is the fork of the dilemma you’re forced to take if you want to avoid nonlocality. “Einstein did not assume realism,” Maudlin said. “He derived it.” Put simply, Einstein ruled out local antirealism, Bell ruled out local realism, so whether or not physics is realist, it must be nonlocal.
> The beauty of this reasoning, Maudlin said, is that it makes the contentious subject of realism a red herring. As authority, Maudlin cited Bell himself, who bemoaned a tendency to see his work as a verdict on realism and eventually felt compelled to rederive his theorem without ever mentioning the word “realism” or one of its synonyms. It doesn’t matter whether experiments create reality or merely capture it, whether quantum mechanics is the final word in physics or merely the prelude to a deeper theory, or whether reality is composed of particles or something else entirely. Just do the experiment, note the pattern, and ask yourself whether there’s any way to explain it locally. Under the appropriate circumstances, there isn’t. Nonlocality is an empirical fact, full stop, Maudlin said.”
Let’s suppose Zeilinger is right. Before any of the entangled particles are measured, none of their properties exist. But as soon as one of them is measured (say positive spin), must the other particle not be forced to come up as a negative spin? Note that the other particle does not have a defined spin before the first one is measured. So how can this be explained without a non locality, perhaps faster than light, or perhaps even an instantaneous influence?
A common retort to this is that according to relativity, we don’t know which measurement occurs first. But then change my example to a **particular** frame of reference. In that frame, one does occur first. And in that frame, the second particle’s measurement outcome is not constrained until the first one is measured. How is this not some form of causation? Note that if there is superluminal causation, relativity would be false anyways, so it makes no sense to use relativity to rule out superluminal causation (that’s a circular argument)
Let’s assume that the many worlds interpretation or the superdeterminism intepretation is false for the purpose of this question, since I know that gets around these issues
