Imagine you found a pair of dice such that no matter how you toss them, they always
added up to seven. Besides becoming the richest man in Vegas, what you would have
there is something called an entangled pair of dice. When you tossed one of the dice,
you would have no idea what number would come up until you saw it, but as soon as
you saw a number, you would know instantly that the other one would come
up such that the two numbers always added up to seven. You could now separate
these entangled dice. You could have your friend Alice take one of these to Macau
while the other one stays with you in Las Vegas.
And as soon as you roll your dice, the other one will always instantly show a number
that added up to seven. Since this happens instantly, did your dice
communicate at faster than the speed of light to Macau? Entanglement is real, and
it has mind-blowing implications for the Universe. What is it? That's coming up right now.
Although entangled pairs of dice is not real, in quantum mechanics
entangled pairs of particles are very real. And they work in a very similar way.
To understand entanglement better, you first have to accept the fact that at the
quantum scale, reality is fuzzy. Reality doesn't know what it is until it's
measured. This is like a single dice tossed in the air that doesn't have a
distinct face until it lands. When tossed up, it is a one, two, three, four, five, and
six all at once. Quantum particles are similar in that
they do not have a distinct property until they are measured. Particles such
as a photon exist in all possible states simultaneously. But when it is
measured, it is in only one state. And if the photon is entangled, this measurement
of one particle causes its entangled pair to simultaneously exhibit the
opposite state no matter what the distances between them. Einstein disliked
this idea of one particle influencing the other over long distances so much,
that he called it "spooky action at a distance."
Einstein believed that the particles carried information about each other at
the moment they were entangled, and were close to each other. In other
words, the properties of both particles were determined locally and carried along
from the very beginning. So in Einstein's view, the two dice knew what
they would show before they were tossed. But in the quantum world, this is
supposed to be impossible because particles don't know what they are until
they're measured, like the dice being simultaneously all numbers when tossed.
But Einstein's view was something that many scientists held on to because his
view of predetermined entangled particles could not be disproven. But in
1964 an Irish physicist by the name of John Bell devised a test that actually
could prove whether information was encoded within the entangled particle or
whether the "spooky action at a distance" was real. He did this by taking advantage
of the fact that in quantum mechanics, measurement affects the thing you are
measuring. If information was encoded at the time of particle creation as Einstein
believed, then nothing we do randomly to one particle should affect the other. And
what this test found conclusively proved that quantum mechanics is correct, that
Einstein was wrong, and that "spooky action at a distance" does in fact does take place.
And since 1964, numerous experiments have proven this over and over again.
Einstein's worst fear is true. There are no hidden bits of reality that act locally
to predetermine quantum measurement results. So are entangled particles
communicating instantaneously. If any communication does exist, it is at least
ten thousand times faster than the speed of light. That's what we know. But this
fact doesn't matter. Even if the speed was five miles per hour faster than the
speed of light, it would violate Einstein's theory of relativity. More
importantly, our picture reality would completely collapse. So let's just say
that most scientists have come to the conclusion that no faster than light
communication is taking place. So if no signal is telling these particles how to
coordinate the results, what's going on? The answer has to do with the
unintuitive way that quantum physics works.
We humans are just not comfortable with dealing with reality
that, at its fundamental level, is fuzzy, uncertain, undetermined. Or is it?
There is another real possibility that is not popular among scientists, but that
Bell himself proposed. And that is called super determinism. And here is how
it could solve the mystery of entanglement. Bell proposed the idea of absolute
determinism in the universe, the complete absence of free will. Suppose everything
in reality is predetermined. It cannot be changed. The reality that you live in has
already happened. No matter what you say or do, nature runs like a clock
unchanging. Our behavior and decisions, including our belief that we are free to
choose, to do one experiment rather than another is absolutely predetermined.
There are no real choices like the experimenter choosing to carry out one
set of measurements, rather than another. There is no real randomness. If this is
the case, the mystery disappears. There is no need for faster than light signals to
tell particle "A" what measurement has been carried out on particle "B"
because the universe including particle A already knows what the measurement
will be. It is predetermined. Could this be the real reality? Could Einstein have been
right all along...that God does not play dice with the universe, that all time and
all fate is predetermined?
Could it be as a religious person might say, "everything is written?"