🚀 go-pugleaf

In article <Bx7Cot.4D7@well.sf.ca.us> sarfatti@well.sf.ca.us 
(Jack Sarfatti) writes:
|I woke up this morning realizing that, of course, if the two beams into the
|splitter ar coherent and 90 degrees out of phase then one output port will
|have no signal due to constructive interference because of extra 90 degree
|shift of splitter. In this special circumstance splitter is not
|"irreversible". But his trick can be used to get a single |h> in my
|experiment.  Put a 90 degree shift phase plate in path of one output of
|first recombiner then use second beamsplitter so that all of the signal
|goes to only one counter.  

Will it, in your experiment, really always be 90 degrees? Won't it
rather have to be by an angle which will complement the phase shift
introduced by your earlier phase plate, and hence prevent you from
modulating the phase difference at the "transmitter"?

|Now Ramsay don't say we have to worry about
|phase variations because lots of interferometers work this way.  For
|example, a Mach-Zehnder.

I'm willing to address the various comments you have recently made,
but I think you should have to get the optics of your beam splitters
and recombiners correct first. How are you going to recombine two
beams so as to get a fixed final result, *and* simultaneously modulate
the phase of one of the beams?

It is of course possible to split a beam. One can have photons enter
in an initial state |a>, and exit in a state which is a superposition
(|b1>+|b2>)/sqrt2 of states |b1> and |b2> corresponding to photons on
two distinct output paths. This can be reversed as well: one can have
an analogous beam splitter which evolves a state of the form
(|b1>+|b2>)/sqrt2 back to one of the form |a>.

What you *can't* do, unitarily, is arrange for both |b1> and |b2> to
evolve back to (multiples of) the same |a> separately. I sincerely
hope that you are not attempting to do this.

I will wait until you describe your latest version of the experiment
specifically enough to make what it is you *are* trying to do
unambiguous, or admit that this latest idea doesn't work.

Keith Ramsay         "But I really think that frequent posters such as 
ramsay@unixg.ubc.ca  myself, Dale, Scott, McIrvin and others are not 
                     crackpots; we are simply loudmouths."
                                        -John Baez