The point now in these early days is to
investigate physical systems of the sort that just haven't existed before
It's to make something that when you see or measure its properties, it's like wow.
Atoms have never behaved that way before.
Light has never behaved that way before.
So, the beginning of this is having few quantum things, whether they're electrons or photons
or atoms, talking to each other in this quantum language
Which if the system's open to the world, there's just too much noise coming in.
Imagine you're walking along and trying to have a conversation in your special language,
You know, so you start talking and boom, in comes a ping pong ball and hits him in the
head.
And so that constant bombardment disturbs any train of thought about having this conversation
in a quantum language.
A simple way to think about it is in the quantum world, everything, electrons are not little
bee-bees, little tiny particles of little tiny bowling balls, but they're really waves.
It actually goes up and down, up and down just like a water wave
So if you have a nice, perfectly calm day and you're going to put your finger in and
then have the waves spread out perfectly calmly, that's like an electron moving through a solid.
But if the wind's blowing, then you get all these other little wavelets that interfere
with this beautiful single wave
So by the time you're through you don't see the nice wave ... it doesn't have any coherence
left
That's famously formulated by Einstein 100 years ago; they call the fluctuation dissipation
theorem.
If these fluctuations of things coming in to mess up the quantum system, then the atom
dissipates its beautiful quantum stuff into the environment.
So all you have is this envelope of energy without the actual waves.
And the quantum physics is in the waves.
So typically, to have really interesting Quantum phenomena, you have to just get rid of all
the interactions, all the people out there throwing ping pong balls.
You gotta get rid of that!
That is a lot of equipment.
Yes it is.
So what you see here is a source for atoms.
We try to create a pipe that guides the photon and the atoms into the pipe, so there's no
way they can avoid each other.
They have to interact.
So, how do we do that?
The way we do it, is
It generates a cloud of cesium atoms.
We shoot it to the center of the chamber here, and
We create six laser beams.
So inside this laser field, they form some kind of molasses.
No matter which direction they go, we always trick the atom so they keep losing energy.
The motion gets damped, and it moves very, very slowly.
This chip sits at the center of the chamber.
In this window, there's a 200-nanometer thick, 300-nanometer wide, we call it Alligator Waveguide.
The reason is because it's two parallel beams, and it's the inverse of the alligator shape.
So, this shape might look very weird, but we use these teeth to create a situation that
when photons propagate along the waveguide
all these teeth, they create interference, then, the speed of light is slowed down.
Then the intensity of photons is strong here, weak here, strong here, weak here, strong
here...
When atoms see strong intensity, they get kicked out by the photon.
It has a repulsive force.
So we can guide this atom into this kind of dark spot, here.
At the same time, we can send another frequency of light, which brights up at the dark spots.
It's the magic of this kind of Alligator Waveguide.
So, we achieve both, guiding the atoms and then have them interact strongly with the
photons.
Otherwise, it would be like atoms are flying around, and I shine a big white flashlight,
just hope that my flashlight can hit the atom.
But using this kind of lithographically patterned waveguide, we can create array of tiny little
traps.
So if one atom gets excited, it emits a photon, this photon can travel down to the waveguide,
talk to another atom.
And then, this atom changes the properties of this photon, and then, again, propagates
down the waveguide and then talk to another atom.
By doing this, we can create a Quantum Simulator of many, many Quantum objects interacting
with each other.
And if I just let the system evolve, what would the answer be?
We've done experiments, other people have done experiments, where you can make a state
where you have 2 beams of light.
And this 1 has a photon and this 1 has nothing, or this 1 has a photon and this one has nothing.
And those 2 possibilities can exist at the same time.
There's only 1 photon, and it's in both places at the same time.
and we've done experiments to demonstrate that that's true, that we've really made a
state like that.
In our experiments we took those pieces of a photon, if you will.
It's called entangled.
and we put them into a bunch of atoms.
How would those 2 parts of a photon propagate?
How would they see each other?
The easy thing to say is this piece of the photon could be absorbed by the 5th atom,
and that piece of the photon could be absorbed by the 35th atom.
And then they would both come out.
And then they would rattle around some more,
And then this quantum pinball, if you want to call it that way, the photon bouncing around
or a photon in 2 pieces or 5 photons in 25 pieces,
that can get real complicated in the way the waves interfere, as the photons run up and
down,
Cause they're not BeeBees as I've been describing them.
What really happens is a photon can be absorbed simulataneously by all the atoms.
And then each of the atom has, if there were 20n atoms, each of the atoms has only a 20th
of a photon.
And now you say, which atom is it in?
It's 1/20th in all the atoms at the same time.
If I gave you this thing and you were going to play with it, it's got an input and output
on 2 ends.
You send light in, get light out, change the frequency of light, send impulses
You look at how many come in and out, and you would say being a trained physicist, you
would say, "What the heck is inside of there?"
I would say, isn't it neat?
You know?
The point now in these early days is not let's make quantum computer
It's to build quantum systems that are surprising.
With characteristics that just haven't existed.
Now the boundary has pushed into very different parts of physics that I've ever been comfortable
with or knew anything about.
That technology of how you do that, how you build those, my group knew nothing.
But that's what you're supposed to be doing.
If you want to be at the cusp of the future, you have to be willing to fail.
We've come up some climb, and didn't work, you better go down, try another way.
You better believe it's scary.
But it's an exhilarating intellectual adventure.
In my position, wow, it's a priviledged position to be able to explore.
So if you know what you're doing...
Don't do it!