M1L4k.txt

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# Captions for 8.422x module
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So what I've just told you has traumatic consequences for any
form of non-classical or [? squeezed ?] [? slide. ?] And
that's the following.
Most of you are experimentalists,
and you know that when you run a laser at one or two watt,
you send it through optics, and shudders, and optical fibers.
How much do you get at the end of your experiment?
Not even 50%.
So whenever you create light and then you want to do something,
you lose some of the light.
And let's now assume that you have done what was really
been a breakthrough in scientific headlines
within your lifetime.
You have generated squeezed light.
And now you want to use the squeezed light,
shine it on atoms, and do a precision measurement, which
is better than [? understand that ?]
quantum limit because you have squeezed the ellipse,
and you want to now exploit the sharpness of the ellipse.
What happens to your aspect ratio of the ellipse
when your beam is attenuated?
So let me just discuss it with you graphically.
So let's assume we have a squeezed state
and we send it through an optical fiber.
The result is you will never send the squeezed state
through an optical fiber, but I want you to realize it.
So let's assume we have our squeeze state, symbolized
by that.
And now in the time evolution, we
have some Rayleigh scattering.
Some fiber absorption.
But you know already the absorption
is, in reality, a beam splitter, which [? couples ?]
in the vacuum.
So we have now some finite transmission coefficient.
And that would mean-- which is the bad news--
that your ellipse gets shrunk.
It shrinks by the transmission factor, T. That's already bad.
You lose some of your power.
But the really big thing is that with [INAUDIBLE]
and multiply it with the reflection coefficient,
you couple in the vacuum.
Oops, I want to change to red.
And as a result, since the noise in the vacuum
is equal in both quadrature components,
you've worked so hard to squeeze it, to make asymmetric.
But what you get now is-- well, from your ellipse,
you get something which is much more egg shape now.
So in other words, you can write it down with operators.
But once you understand what is going on,
you immediately realize that losses reduce the squeezing.
And this is a challenge to all experiments using squeezed
or non-classical light.
And you see how the scaling works.
If you have squeezed your ellipse by a factor of 100,
even 1% of the vacuum will spoil your squeezing.
So the more you have squeezed, the more
non-classical the light is, the more valuable it is,