Can the quantum state be interpreted statistically?

Can the quantum state be interpreted statistically?(mattleifer.info)

41 points by davidmathers 14 years ago | 6 comments

redwood 14 years ago |

The book "How the hippies saved physics" has some really interesting historical observations about the shift in academic physics from before WWII into the Cold War era (and largely from Europe to America).

The crux is that a physics of philosophy, heavy on theory, was largely replaced by a physics of "engineers in reserve" to be pumped out by universities as a necessary weapon in order to win the Cold War. Of course the weapon was fairly successful, as we saw physics pave the way for new applied engineering, computer development, and chemistry. But it's also true that the basic tenet of early-20th century theoretical physics---that of questioning the established narrative---largely disappeared in this era.

Now things are changing again, there are enough educated individuals to study every conceivable angle; there are mainstream stories in the press about special relatively potentially facing caveats like never before, etc. All in all it's an exciting time and healthy that debate is more full again.

The long established narrative in (especially American) academic physics that there is no questioning of quantum mechanics, and no use hoping for a deeper theory, is a great example of group think. Sure maybe we'll never have a deeper theory, but we should always try to find one!

jerf 14 years ago | |

"The long established narrative in (especially American) academic physics that there is no questioning of quantum mechanics, and no use hoping for a deeper theory,"

Really? The narrative I've heard is that we know Relativity and QM don't go together very well and it's clear that we need something beyond the both of them to figure out how the universe works at all scales. And physicists in general seem pretty excited about any tidbit of data that might contradict one or the other, because they desperately need clues about what the non-QM/non-Relativity answer looks like. Who is out there saying that we must not look for anything beyond QM?

Dn_Ab 14 years ago | |

A lot of people do spend time on foundations but for most physicists and their day to day work worrying about such things is like a programmer worrying about the Halting problem or whether the problem is in NP or a mathematician worrying about the second incompleteness theorem or even Russell's paradox. Sure those are deep results but they have to get on with their work.

But things have moved on with foundations and if you read about what is called the neo-copenhagen interpretation you will find a lot of the hoopla and confusion of quantum mechanics goes away and the door is opened to even more astounding interpretational consequences.

Dn_Ab 14 years ago |

See also this entry http://www.scottaaronson.com/blog/?p=822 and its comments at Scott Aaronson's blog.

Dn_Ab 14 years ago | |

for other lay people watching - the original paper was over hyped. There is an interpretation of quantum mechanics that basically thinks that the state of a quantum object is more or less sampled from an underlying reality that we cannot fully capture. This viewpoint is not widely held, even a lay person such as myself found it to not make much intuitive sense - it seemed like another way of sweeping hidden variables under a rug.

Anyways the paper now mathematically refutes this viewpoint. It still leaves untouched another probabilistic view point that the state represents no underlying reality and that quantum mechanics is an extension of bayesian probability theory to a complex space (this is the view I think makes the most sense).

In essence the paper simply solidly codifies what most of the physicists already accepted. So not much changed.

Estragon 14 years ago |

This really helped me to understand the thrust of the paper. Much better than Motl's rant.