Albert Einstein was, there’s no other word for it, a genius.
The man conceived of special and general relativity,
theories that have been breaking brains since the early 1900s.
But when it came to the idea that two particles can be entangled,
and an effect on one could be instantaneously felt by the other even over vast distances,
for Einstein that was simply unbelievable.
He dubbed it “spooky action at a distance,” and went to his grave a skeptic.
But since then, quantum entanglement has been demonstrated time and again,
and now, for the first time ever, we’ve taken a picture of it.
To achieve this, researchers from the University of Glasgow shot an ultraviolet laser at a crystal,
which broke apart some of the photons from the beam, creating two entangled photons.
When particles are entangled their properties or states, like spin or phase polarization, will be linked.
But until they are measured, those properties will remain in superposition,
meaning it can be in multiple states at once.
Observing one particle will make it take on one state, while at the same exact moment,
it’s entangled twin will take on the opposite state.
The entangled property of the photons the researchers chose to observe was their phase.
Remember that photons can behave as both particles and waves,
and a photon’s phase is where it is in its wave oscillation.
Photons that are in step, or in phase, can amplify each other to give a brighter intensity,
and out of phase, they can cancel each other out to give darkness.
Once these entangled photons were created, they were split and sent on different paths.
Down one path, the scientists set up a filter that would limit the photon to one of four different phases.
Passing through the filter is effectively the same as observing the photon’s phase,
so as soon as its phase was determined,
its entangled partner traveling down the other path would take on the opposite.
Finally, when the two entangled photons in opposite phases were simultaneously detected,
a super-sensitive camera capable of detecting individual photons would take a picture.
Scientists repeated this until they could build an image of the entangled photons,
allowing the waves to amplify and cancel each other out.
And without further ado, here it is.
The photons look like eyes, so “spooky” definitely seems like the right word for what we’re looking at.
If you look closely, you’ll notice two gaps in the circle where the intensity smoothly drops off to zero—
that’s the phase the scientists were measuring.
And this picture further counters how Einstein thought quantum entanglement could work.
To make entanglement jibe with classical descriptions of physics,
he proposed so-called “hidden” variables that would act as a messenger between entangled pairs.
When he proposed this, no one knew how to test if a hidden variable was at play,
or if the quantum world was just really weird.
In 1964, almost a decade after Einstein’s death,
physicist John Bell came up with a theorem
that can distinguish between Einstein’s proposed hidden variable explanation of spooky action,
and quantum mechanics’ entanglement explanation.
These statements are known as Bell’s Inequalities, and years after he devised them,
they were tested and contradicted Einstein’s idea of a hidden variable.
This photo adds to the pile of evidence against Einstein,
violating Bell’s inequality that assumes the hidden variable interpretation.
So, now you have a picture to put in your locker next to that photo you have of Einstein with his tongue out.
It may serve as a nice reminder that your name can literally be synonymous with the word “genius,”
and you can still get stumped sometimes.
It’s a good thing quantum entanglement is real because it’s key to a quantum computer.
If you want to see how close we are to finally building one, check out this Focal Point episode all about it.
What’s the coolest picture you think science has ever produced?
This entangled photons picture,
a black hole, or something else?
Let us know in the comments, be sure to subscribe while you're down there,
and I’ll see you next time on Seeker.