It looks like a fuzzy, neon-green doughnut. Or maybe a blurred horseshoe. To the untrained eye, the 2019 image released by researchers at the University of Glasgow doesn't look like much. But honestly? It’s one of the most significant photographs in the history of science. It’s the first-ever picture of quantum entangled photons, and it proves that the universe is way weirder than our common sense wants to admit.
For decades, entanglement was a math problem. A ghost in the machine. Albert Einstein famously hated it, calling it "spooky action at a distance." He spent years trying to prove it couldn't be real because it violated the cosmic speed limit—the speed of light. Then, suddenly, we had a digital file. A visual receipt.
Why a fuzzy green blur changed physics
The image represents a phenomenon where two particles become so deeply linked that one literally cannot be described without the other. Distance doesn't matter. You could put one photon on Earth and its partner on the Moon; if you tickle one, the other reacts instantly.
This isn't just theory anymore.
Dr. Paul-Antoine Moreau and his team didn't just snap a photo with an iPhone. They built a massively complex system involving a specialized laser that fired through "non-linear" crystals. These crystals occasionally split a single photon into two. When that happens, those two "daughter" photons are entangled.
The team used a technique called "super-resolution" imaging. They set up a system that only triggered the camera when it detected both photons at the same time. What you see in the picture of quantum entangled photons is actually a composite—a cumulative record of thousands of "coincidence" events.
The Bell Inequality and the proof in the pixels
To understand why this image matters, we have to talk about John Bell. Back in the 60s, he came up with a mathematical way to test if Einstein was right (that there was some "hidden" information we just couldn't see) or if the universe was truly as random as Bohr and Heisenberg claimed.
The Glasgow image is a visual manifestation of a Bell Inequality violation.
By passing the photons through liquid crystal materials that changed their phase, the researchers forced the particles to "choose" a state. If the particles weren't entangled, the resulting image would have been a chaotic mess or a uniform blob. Instead, we got those distinct, organized patterns. It was the universe screaming, "Yes, I really am this strange."
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How do you actually photograph a ghost?
It’s not like taking a portrait. You can't "see" a photon in the traditional sense because the act of seeing it—the photon hitting your eye or a sensor—usually destroys it.
The researchers used a high-sensitivity camera capable of detecting single photons. It’s called an ICCD (Intensified Charge-Coupled Device).
Imagine a dark room. You have a machine gun firing pairs of invisible bullets. You want to prove the bullets are "twins." You set up two targets. Every time a bullet hits Target A, you check Target B. In the quantum world, if the bullets are entangled, they will always hit the exact same relative spot on their respective targets, even if you try to deflect them.
The picture of quantum entangled photons is the "scuff mark" left behind by billions of these twin bullets hitting the sensor at the exact same moment.
Common misconceptions: What the image ISN'T
People get this wrong all the time.
You aren't looking at two particles sitting next to each other. You are looking at the probability distribution of where those particles ended up. It’s a map of their relationship, not a selfie.
- Misconception 1: The green color is "real." No. The sensors detect light, and the green color is added via software to make it visible to human eyes. Most quantum experiments happen at wavelengths we can't see anyway.
- Misconception 2: This is a live video. Not even close. It took an incredible amount of time and thousands of frames to "build" enough data to show the pattern.
- Misconception 3: It proves we can send messages faster than light. This is the big one. Even though the particles are linked, you can't use them to send a text message to Mars instantly. Why? Because the results are still random. You can't "force" the Earth photon to be a specific way to tell the Mars photon what to do. You only see the link after you compare the data from both sides.
Why should you care about a blurry horseshoe?
It's easy to dismiss this as "nerd stuff." But this image is the foundation of the next hundred years of technology.
We are currently in the middle of what scientists call the Second Quantum Revolution. The first one gave us the transistor and the laser (and thus, the internet). This second one is about using entanglement.
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Quantum Computing
Traditional computers use bits (0 or 1). Quantum computers use qubits, which take advantage of entanglement to perform calculations in parallel that would take a MacBook billions of years. When we see a picture of quantum entangled photons, we are looking at the "wiring" of the world's future supercomputers.
Unhackable Encryption
If you try to "eavesdrop" on an entangled photon, you break the entanglement. It’s like a wax seal on a letter that vaporizes if a stranger touches it. Companies are already using this for "Quantum Key Distribution" (QKD).
The human element: Why Einstein was bothered
Think about the implications for a second.
If two particles can be linked across the universe, it means that "locality"—the idea that things are only affected by their immediate surroundings—is a lie. It suggests a level of interconnectedness that feels more like philosophy or religion than hard science.
Einstein called it "spooky." Most physicists today call it "business as usual," but even the most seasoned researchers admit that, deep down, it’s still weird. Seeing it in a photo makes it real in a way that an equation on a chalkboard never can. It moves the conversation from "what if" to "look at this."
The technical hurdles of the Glasgow experiment
The team, led by Miles Padgett, had to overcome staggering noise. In any quantum experiment, "noise" is the enemy. Heat, vibration, even the smallest amount of stray light can ruin the entanglement.
They used a "Sagnac interferometer." This is a device that splits a beam and sends it in two different directions around a loop before recombining it. It’s incredibly stable. By using this, they ensured that the only thing the camera captured was the genuine correlation between the photons.
The resulting image shows four different phases of entanglement. It’s not just one picture; it’s a gallery of quantum states.
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Actionable insights: How to follow the quantum trail
If this fascinates you, don't just stop at the photo. The field is moving at breakneck speed.
Watch for "Loophole-free" Bell tests. While the 2019 photo was a milestone, researchers are constantly closing "loopholes"—potential ways that classical physics could explain away these results. Look up the work done at TU Delft or NIST for the most recent breakthroughs.
Check out OpenQASM. If you want to play with entanglement yourself, IBM offers free access to real quantum computers through the cloud. You can write a small script to entangle two qubits and see the statistical results yourself. You don't need a PhD; you just need a bit of curiosity.
Follow the "Quantum Internet" progress. Institutions like the Brookhaven National Laboratory are currently building long-distance quantum networks. They aren't just taking pictures anymore; they are "teleporting" information across miles of fiber optic cable using these entangled pairs.
The picture of quantum entangled photons was a beginning, not an end. It turned a ghost into a silhouette. As our imaging technology improves—using things like "Ghost Imaging" (where one photon creates an image of an object it never actually touched)—we are going to see deeper into the fabric of reality.
Physics is no longer just about measuring things you can touch. It’s about mapping the invisible threads that hold the whole thing together. Next time you see that blurry green doughnut, remember: you’re looking at the first time humanity caught the universe's most private secret on camera.
Next Steps for Deep Exploration:
- Visit the IBM Quantum Learning platform to run your first entanglement circuit on a 5-qubit processor.
- Search for "Ghost Imaging with Entangled Photons" on Google Scholar to see how this tech is now being used to image biological samples without damaging them with high radiation.
- Download the original paper "Imaging Bell-type nonlocal behavior" from Science Advances (it’s open access) to see the raw data plots that sit behind the famous green image.