Mark Megahan
Usually, it’s art imitating nature but in this case, the nature of entangled photons imitates the Zen symbol for unified yin-yang duality. It’s incredibly fitting. You can’t just whip out the Instamatic and grab a snapshot of the quantum object but researchers found a way to image it anyway. They call it “biphoton digital holography.”
A holograph of entangled photons
Tangled photons are funky enough but this, scientists brag, is something entirely new. They used “a first-of-its-kind technique to visualize two entangled light particles in real time.”
The most surprising thing about their result is that it produces a perfect “yin-yang” symbol pattern.
Through the novel method of biphoton digital holography, Alessio D’Errico and his team at the University of Ottawa in Canada use “an ultra high-precision camera.” Their shortcut method “could be used to massively speed up future quantum measurements,” they note in a recently published study.
They’re studying a phenomenon Albert Einstein called “spooky action at a distance” because two paired photons can communicate instantly even if they’re on opposite sides of the universe. That means faster than light information exchange.
Folks who actually understand the math behind these quantum wonders can use a “wavefunction” as a map to “make accurate predictions about a quantum object.”
It’s basically a “description of its state existing in a superposition of all the possible physical values a photon can take.” Entangled photons are even trickier to track because “any measurement of one also causes an instantaneous change in the other.” They figured out a way around that.
Quantum tomography
Physicists invented a sort of quantum level CAT (Computed Tomography) scan they call “quantum tomography.” By “taking a complex quantum state and applying a projection to it, they measure some property belonging to that state, such as its polarization or momentum, in isolation from others.”
The tedious part is “repeating these measurements on multiple copies of the quantum state.” They keep measuring the tangled photons until they “can build up a sense of the original from lower-dimensional slices.”
They say it’s a lot like “reconstructing the shape of a 3D object from the 2D shadows it casts on surrounding walls.” The process “gives all the right information, but it also requires a lot of measurements and spits out plentiful ‘disallowed‘ states that don’t follow the laws of physics to boot.”
That’s a lot of work. Photons are complicated particles. “This leaves scientists with the onerous task of painstakingly weeding out nonsensical, unphysical states, an effort that can take hours or even days depending on a system’s complexity.”
That’s where the breakthrough comes in. “To get around this, the researchers used holography to encode information from higher dimensions into manageable, lower-dimensional chunks.” You may be familiar with three dimensional optical holograms. There are some really wild genuine laser produced ones to be found. In the one of a microscope below, you can actually see through the eyepiece to find the insect being examined on the slide. There are also a lot of cheesy optical illusions billed as holographs and fantasy images from the Hollywood special effects department.
Proper optical holograms “use two light beams to create a 3D image: one beam hits the object and bounces off of it, while the other shines on a recording medium. The hologram forms from the pattern of light interference, or the pattern in which the peaks and troughs of the two light waves add up or cancel each other out.” It works the same for entangled photons. They captured an “image of the entangled photon state through the interference pattern they made with another known state.” It took a “nanosecond precise camera” to do it. What they ended up with is a distinctive “yin-yang” pattern and they got the results “exponentially faster” than with previous techniques.
