M1L5a_CQ0.txt

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What is the nature of shot noise?
The whole kind of set of questions
will build up to teach you something
about what is shot noise.
In other words, when you measure in photons
and you start with coherent beams,
you always have sort of square root n.
And the question I want you to ask
is, when we measure square root n fluctuations,
where will you the n photons?
Is this caused by the nature of the measurement process, sort
of how will would you take photons that--
or is it an intrinsic quantity of the quantum fields?

So I just want to sort of to get your intuition,
your gut feeling, whether shot noise is rather-- it's maybe
not black and white, but if you think
it's more related to the measurement-- let me write it
down.
Shot noise-- oops.

OK, so the question is-- so the question is shot noise,
is it caused by the quantum measurement process, projection
of whatever you know about it?
Second question, second part, is it property
of the quantum fields?
For instance, if you don't make a measurement,
if you're on the quantum fields or beam splitter,
we can split it.
We can split the shaft noise even before we measure it.
That would mean quantum fields.
And maybe then third is both.
And the fourth is none of the above.
So let's just take an opinion.
And maybe [INAUDIBLE]-- I'm not discussing the answer at this
point.
I will come back to that at the end of those 10 or 15 minutes
and ask you the question again.
So I just want to see how-- sort what
your intuitive understanding is when you measure
the number of photons in a laser beam in an optical field
and you see fluctuations, quantum
measurement versus properties of a quantum field.
Quantum measurement means mainly cause the moment you detect it.
And quantum fields means it's there already before