This thought experiment will help you understand quantum mechanics Matteo Fadel
After a long day working
on the local particle accelerator,
you and your friends head to the arcade
to unwind.
The lights go out for a second,
and when they come back,
there before you gleams a foosball table
nobody remembers seeing before.
Always game, you insert your coins.
And with a fanfare,
Quantum Foosball begins.
Here are the rules:
as with normal foosball,
the object is to score points
by spinning levers with tiny players
to sink the ball in your opponent’s goal.
Only instead of a standard ball,
you’ll be playing with a giant electron.
It behaves like a normal electron
in all respects, it’s just much larger.
Though the rules are simple,
gameplay is anything but.
Instead of the familiar laws
of Newtonian physics,
the movement of the ball is governed
by quantum mechanics.
To minimize the influence
from photons and air molecules,
you’ll be playing in a vacuum.
In the dark.
But that’s ok, because you can watch
for the flashes of light
given off by collisions
between figures and the ball.
The goals themselves will flash
when the electron
hits their particle detectors.
Now you just have to figure out how
to get the electron to go where you want.
As soon as it enters play,
the electron will never rest.
This is a direct consequence
of the Heisenberg Uncertainty Principle,
which says that the better you know
where a quantum particle is,
the less you know about its velocity,
and vice versa.
Since you know it’s on the field,
its velocity is largely uncertain.
The electron will behave more like a wave
than a particle,
with its position described by probability
distributions that you’ll have to imagine.
These distributions are spread throughout
the entire field,
making it possible to observe a goal
at any time and in either side.
The way to win is to control
and concentrate the distribution
over the opposite goal,
giving yourself the highest likelihood
of scoring points.
Your skill as a player will be determined
by your ability to predict
where the electron is most likely to be,
then manipulate the probability
distribution by spinning the rods
with just the right amount of strength.
Quantum particles only receive energy
in precise amounts, called quanta.
So spin too hard or too soft,
and the electron will stay
on its previous course.
The game board has been carefully
constructed to contain the electron,
but even so, sometimes it’ll quantum
tunnel through the walls
without any apparent reason.
At that point it could be anywhere
in the universe,
so to save you the trouble
of tracking it down,
the game will spit out a new ball.
The fact that quantum particles behave
like waves
becomes particularly evident
in the presence of obstacles.
As the particle travels through the rows
of miniature figures,
complicated interference patterns will
develop in the probability distribution,
making it even more difficult
to accurately predict its position.
And here’s where your advanced physics
degree can finally come in handy:
you can use the laws of quantum mechanics
to your advantage.
The only moments when the electron
will behave as a particle,
rather than a wave,
are when it hits something.
With frequent enough kicks,
the particle would have no time to evolve
like a wave and, therefore,
not spread out in space.
So if you can pass it very quickly
between two of your miniatures,
you can keep it localized.
Masters of the game call this
the Quantum Zeno Maneuver.
Now, if you really want to dominate
your opponents,
there’s one more thing you can try,
but it’s pretty tricky.
One of the distinctive features
of the quantum world
is the possibility
of state superpositions,
where particles’ positions or velocities
can be simultaneously in two or more
different states.
If you can put the electron
into a superposition
of being simultaneously kicked
and not kicked,
it’ll be almost impossible
for your opponents to figure out
where and how to strike.
It’s said that Erwin Schrödinger,
the greatest Quantum Foosball champion
of all time,
is the only player to have mastered
this technique.
But maybe you can be the second:
Just figure out a way to simultaneously
turn and not turn your rods.