Jim Lesurf in uk.rec.audio:

Interesting, what was considered the lowest possible unit of
information?

My memory is unreliable on this as I only came across references to it
many years ago. Note they weren't regarded as the 'lowest unit' any
more than a metre is the 'lowest unit' in the sense of being
indivisible. IIRC one unit was based upon 'e'. I think these units
appear in, for example, some of the books on the work at Bletchly Park
during WW2. Afraid I'd need to find the books and search through them
to see what I could find about this, although I suppose it may also be
"out there" on the web as most things are, these days!

I sometimes think of 'half bits' as a theoretical thing but know that
half a bit cannot really be transmitted.

Depends upon what you mean. Symbols (and hence symbol patterns) can
quite easily communicate non-integer amounts of information as
measured in 'bits'. Indeed, if you do an entropic analysis of English,
most letters in a meassage contribute a non-integer amount of info.

This makes sense if I understand correctly. 'qu' contains less than two
letters' worth of information in English since q is almost always
followed by u.

Its interesting that people do tend to think that the 'bit' is somehow
a different kind of unit to a 'metre' or a 'kilo' or a 'degree'.
However it is just a defined amount used as a reference for
measurement purposes. Just happens to have become so much the standard
that no-one even thinks of using an alternative.

I'm venturing a guess here, but I can see how less than a bit's worth of
information can be transmitted, but not less than a bit of actual data. I
may have the definitions wrong, what I mean is that one bit may have less
informational significence than another, but no smaller unit may be
transfered in a digital system.

When I first mentioned half-bits I was thinking back to ZX days again, in
which I'd sometimes set up, for example, one 5.5 and one 2.5 bit value in
a byte. Memory really was tight in those days!

I suspect I'll be retired before 'quantum computing' really makes
an impact. This will be useful as I may need the spare time to
really understand it.

Ambitious!


Well, I'm hoping to live long enough... although this may take a
while. ;-)

I think I understand most the fundementals now, its difficult because we
don't normally have to think of things like a quantum guess as being
compatable with the 'real world'.

[1] Can of worms. :-)
[in reference to a pure random source]
I take it you mean the 'random yet deterministic' thing; a program for
the digits of pi gives random numbers, but deterministic random numbers.
It goes beyond what we comonly think of as random for it to be
deterministic. Most computer PRNGs just stretch and fold with very large
period.
There is a 'hotbits' web server somewhere that provides completely random
numbers free to academics, using quantum uncertainty as the source. I
wrote a java implementation of the Random interface that connects to the
server if you ever need it.

--
Jim H