In science, there are times when someone poses a question that is so straightforward that it seems almost absurd, but the response turns out to be anything but. When a group of theoretical physicists at the University of Oslo got together to consider what would happen if they attempted to split a photon in half, that is essentially what happened. Not in a symbolic sense. literally cut one while it was in the middle of its journey, right through its wave.
The fundamental building blocks of light are called photons. They have been studied for more than a century, have no mass, and cannot be divided into smaller parts. When asked what would happen if you sliced one with a fast-closing shutter, the majority of physicists would likely provide a reasonable response: either you get a photon on one side or you don’t. A basic probability. a tidy result. Johannes Skaar, a theoretical physics professor and co-author of the study that was recently accepted in Physical Review Letters, also anticipated this. He was the first to acknowledge that he was mistaken.
Skaar and his associates simulated a situation in which a photon moves in the direction of a mirror using quantum equations. The light wave’s front half hits the mirror and bounces back. The mirror is then abruptly removed, allowing the wave’s trailing half to pass through. There are more than just one or zero photons that emerge from the other side. A superposition of possibilities is produced by the math, ranging from zero photons to, in theory, an infinite number of them. The result is more chaotic the quicker the mirror is removed. You can create an infinite number of light particles from a single particle by pulling it away infinitely quickly, which is mathematically feasible but physically impossible. It’s the kind of outcome that prompts you to pause and read the sentence several times.
The infinity aspect of this discovery isn’t what makes it so peculiar; quantum physicists have mastered the ability to handle infinities with a certain professional composure. The local versus global view of the severed photon is what Skaar refers to. A single photon or nothing at all would be what you would see if you could only see one side of the shutter. a hoover. Completely typical. However, the system appears completely different—a chaotic, churning mixture of photon states—if you could somehow observe both sides at the same time. From one perspective, the same physical event appears calm, but from another, it appears chaotic. Skaar has stated, “That is really crazy,” and it is difficult to disagree.
This goes beyond simple curiosity. The outcome touches on a more profound aspect of particle interactions. Causality, the fundamental idea that causes come before effects, has long been a source of trouble in quantum field theory. Particles have, in a sense, been interacting with everything around them for an infinite amount of time because they are described as waves that extend infinitely through space. This makes it difficult to construct a clear causal picture of any particle interaction. However, a photon with a sharply cut tail avoids this problem. There is a defined endpoint to its wave. For once, the causal chain is evident.
This, according to Skaar’s team, is a first step toward a more ambitious goal: a more straightforward theoretical framework for explaining the interactions of particles, not only photons but also possibly electrons and other quantum particles that are similar to waves.
Daniele Faccio, a physicist at the University of Glasgow, acknowledged that he was initially skeptical of the paper. He read it after that. “The technique is legit,” he declared. By his own admission, he is now openly speculating that studying individual photon behavior at this level may be useful in fields that depend on quantum sensing. I think of gravitational wave detectors. Although it’s still unclear if that potential will come to pass, it’s not easy to rule it out.
The fact that a fundamental question like “what happens when you interrupt a photon mid-wave” exists is quietly remarkable. — is only now being thoroughly examined. The field of quantum mechanics has been around for more than a century. However, it continues to generate corners that have not yet been investigated. It turns out that this specific corner is more bizarre than most people anticipated.
