
Quantum Mechanics Without Maths or Philosophy - nabla9
http://www.articlesbyaphysicist.com/quantummechanics1.html
======
ivan_ah
archive link:
[http://web.archive.org/web/20170615010943/http://www.article...](http://web.archive.org/web/20170615010943/http://www.articlesbyaphysicist.com/quantummechanics1.html)
(w/o images)

Skipping from the complex-valued wave function to its real-valued magnitude is
a good simplification for an introductory article, but I think the need for
complex numbers (the concept of phase) is very important and fundamental.
That's what I would really liked explained? Why do cmplx numbers come up, and
is there a QM-equivalent model using only real-valued functions?

~~~
n4r9
Complex numbers aren't strictly necessary. You could even expand every complex
dimension to a pair or real dimensions and get the same results (roughly
speaking). However this is a bit unwieldy, so the question becomes "why do
complex numbers provide such a convenient representation of quantum theory"?

There is work being done on this sort of thing. If essentially all you care
about are the probabilities of certain observations occurring, then you surely
can represent any theory with real numbers. The field of "generalised
probabilistic/physical theories" attempts to analyse quantum theory without
assuming the baggage of Hilbert spaces etc... [0]. Chris Fuchs also has done a
lot of work on representing quantum state spaces in terms of outcome
distributions over special types of measurements called sic-povms[1,2].

0\. [https://arxiv.org/abs/quant-ph/0508211](https://arxiv.org/abs/quant-
ph/0508211)

1\.
[http://perimeterinstitute.ca/personal/cfuchs/](http://perimeterinstitute.ca/personal/cfuchs/)

2.[https://en.m.wikipedia.org/wiki/SIC-
POVM](https://en.m.wikipedia.org/wiki/SIC-POVM)

~~~
akvadrako
This work (QBism) is certainly intriguing and the promise of deriving the
Schrödinger equation from the Born rule using SIC-POVMs could really change
how QM is understood.

But I wonder why it gets so little attention...

~~~
n4r9
The "radical Bayesian" stance is very difficult to grasp, coming from an
ordinary scientific background. At least it was for me - took months, maybe
years of sinking-in to figure out what Fuchs was trying to say. I think a lot
of people start reading about it, quickly get the (false) impression that it's
solipsistic, and just lose interest.

~~~
akvadrako
To be honest, I still can't understand how it's not solipsistic. If you use
QBism from two different perspectives, like Alice and Bob in a Bell test
experiment, then you'll still either need many worlds or get incompatible
results.

~~~
n4r9
Perhaps it would help to note that in QBism, reality is not denied. Rather,
the objective reality _of the quantum state_ is denied.

Not sure what you mean by incompatible results. Certainly QBism is
incompatible with Many Worlds! The latter states that the quantum state is
real and objective, the former states the opposite.

The QBist horsemen have devoted some attention to the question of compatible
quantum state assignments. See: [https://arxiv.org/abs/quant-
ph/0206110](https://arxiv.org/abs/quant-ph/0206110)

However, Chris Fuchs does not see any problem in someone assigning a
probability-1 belief to a measurement outcome and being proven wrong. See
section 2.2 of
[https://arxiv.org/pdf/1705.03483.pdf](https://arxiv.org/pdf/1705.03483.pdf)

This last point in particular should bring home the point that Fuchs does
think there is an ontological theory underlying physics, but that we are
fooling ourselves about how much of it is objective/observer-independent.

------
WhitneyLand
Sorry pet peeve, but title is not a grammar error, a lot of the world says
maths not math.

Some dictators abuse power for material gain. If woke up dictator of Earth I
think my tyranny would lean more towards standards bodies. Forcing holdouts to
the metric system would actually cost the economy more? Too bad, this is the
cruelty of oppression. I at least would promise not to kill or torture anyone.

~~~
model_s
Maths is short for Mathematics. Quantum Mechanics Without Mathematics or
Philosophy is fine.

------
SomeStupidPoint
Website appears to be refusing connections.

~~~
sliken
Sadly, same here. We need a show HN for replicating a static website via
whatever the currently best value proxy/cache/CDN is.

~~~
mysterypie
How about if HN itself takes a snapshot of the submitted article as soon as it
hits the HN front page? For example, HN could cache the article or generate a
PDF, then if the site doesn't load, the cached version or PDF would be served.

This might be good as a historical resource because even good stuff disappears
off the Internet, and if it made it to the HN front page, it's probably good.
(I know, can't do this because copyright. But the Wayback Machine has survived
by deleting content on request.)

------
dhimes
Maybe. Maybe not.

