Re: quantum of magnetic flux

[John Denker <jsd@MONMOUTH.COM>]

Hi Folks --

1) The charge on electrons and protons is quantized.  In any state with a
definite number of such particles, the charge is a multiple of the
well-known number q_e.

2) Angular momentum is quantized.  In any stationary state, the angular
momentum is always a multiple of hbar/2 and the difference between any two
stationary states is always a multiple of hbar.

3) Current is not quantized.  There is no number xxx such that all currents
are a multiple of xxx.

4a) The flux in coherently-conducting rings is quantized.  This can be
deduced if you know fact (1) above _and_ use the argument that leads to
part of fact (2) above, namely single-valuedness of the wavefunction around
the loop.   Neither fact suffices by itself.

4b) In general, flux is not quantized.

At 08:56 PM 3/8/00 -0800, Bernard G. Cleyet & Nancy Ann Seese wrote:
> According to CB the SQuI Device counts quanta of flux; would this not imply
> that flux is quantized?

In general, flux is not quantized.  Flux in coherently-conducting loops is
quantized.

>  I can understand how it could be since it's
> created by quanta (electrons moving, spinning,  and  revolving).

Quantization of electron number and spin does not by itself suffice to
explain when flux is or isn't quantized.

> Current is quantized,

Current is not quantized.

> but flux also varies w/ distance.

Right.

> If it's still quantized, then may be space is?

There's no evidence that space is quantized.  There's plenty of evidence
that it's _not_ quantized on any lengthscale relevant to the issues
discussed here.