Nature News and the Quantum Frontiers blog reported on a recent poll Anton Zeilinger and colleagues conducted at a quantum foundations meeting in Vienna, and published on arXiv. The poll was designed to gauge the opinions of the participants (which included philosophers of science as well as active physicists) on the interpretation of quantum mechanics. Unsurprisingly, there was no consensus on the “correct” interpretation (from Nature News):

For example, votes were roughly evenly split between those who believe that, in some cases, “physical objects have their properties well defined prior to and independent of measurement” and those who believe that they never do. And despite the famous idea that observation of quantum systems plays a key role in determining their behaviour, 21% felt that “the observer should play no fundamental role whatsoever”.

If I had to toss my 2 cents, I would choose the “physical objects have their properties well defined prior to and independent of measurement” and the “observer should play no fundamental role whatsoever” hats. Of course, measurement can and will affect the state of the system, but I gather the idea was to argue against the idea that . I’m not completely sure if agree that there should be “no fundamental limit to quantum theory” – I still find Penrose’s objective reduction ideas attractive, though only experimental evidence will tell one way or the other.

Sean Carroll posted a graph of the results on his blog and called it the “most embarrassing graph in physics”:

He explained the reason for calling it this as follows:

Think about it — quantum mechanics has been around since the 1920′s at least, in a fairly settled form. John von Neumann laid out the mathematical structure in 1932. Subsequently, quantum mechanics has become the most important and best-tested part of modern physics. Without it, nothing makes sense. Every student who gets a degree in physics is supposed to learn QM above all else. There are a variety of experimental probes, all of which confirm the theory to spectacular precision.

And yet — we don’t understand it. Embarrassing. To all of us, as a field (not excepting myself).

I’d have to agree – it is embarrassing that there is so little understanding of the interpretation of quantum mechanics. The results where the majority did agree were (from Quantum Frontiers):

1. Quantum information is a breath of fresh air for quantum foundations (76%).

2. Superpositions of macroscopically distinct states are in principle possible (67%).

3. Randomness is a fundamental concept in nature (64%).

4. Einstein’s view of quantum theory is wrong (64%).

5. The message of the observed violations of Bell’s inequalities is that local realism is untenable (64%).

6. Personal philosophical prejudice plays a large role in the choice of interpretation (58%).

7. The observer plays a fundamental role in the application of the formalism but plays no distinguished physical role (55%).

8. Physical objects have their properties well defined prior to and independent of measurement in some cases (52%).

9. The message of the observed violations of Bell’s inequalities is that unperformed measurements have no results (52%).

I’ve always felt that the Copenhagen interpretation to be an unsatisfying cop-out to cover the fact that we (still!) don’t understand the theory well enough at a fundamental level. It’s nice to see the amount of recent activity on the topic, though I find the thought that “there will still be conferences on the foundations of quantum theory in 50 years time” a bit depressing..

Sean agrees on Copenhagen and ends on a bit more optimistic note:

All we have to do is wrap our brains around the issue, and yet we’ve failed to do so.

I’m optimistic that we will, however. And I suspect it will take a lot fewer than another eighty years. The advance of experimental techniques that push the quantum/classical boundary is forcing people to take these issues more seriously. I’d like to believe that in the 21st century we’ll finally develop a convincing and believable understanding of the greatest triumph of 20th-century physics.

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