The Cat In The Box

In the age of the selfie and the selfie-stick, it’s worth quizzing ourselves on how a camera takes a picture? By capturing the light that bounces off an object.

But in an experiment, led by Gabriela Barreto Lemos, at the Austrian Academy of Sciences in Vienna, reported in the journal, Nature, the team was able to take a picture of an object, without having a beam of light, or a stream of photons, ever striking—and bouncing off—the object.

Credit: Gabriela Barreto Lemos and co-authors, Austrian Academy of Sciences.
Credit: Gabriela Barreto Lemos and co-authors, Austrian Academy of Sciences.

This quantum camera, if you will, was able to capture a picture, with light that never even set eyes on the object. There were photons illuminating the object, but the photons that struck the object were never detected by it.

The experiment involved tiny cut-out of cats, 0.12 inches tall and laser beams, of different colors, hence, different wavelengths.

A ribbon of light, A, was fired at the feline cut-outs, using a wavelength of light, which couldn’t be detected by the camera.

Next, A was joined by the other beam in the light pair, B. It ran along a separate, parallel track to A—but bypassing the object and along a second stretch. So, while A passed through the object, B didn’t.

A was then, discarded.

The two halves of the photon stream, B, from the two portions of the journey, were then, reunited and directed towards the camera. There, the recombined B created this “photograph” of the cut-out, even though it never went through the cut-out itself.

How then, did this grainy portrait emerge?

The two seemingly independent beams—one that illuminated the cut-out and the one that hit the camera— were behaving like twins, sharing a quantum bond. They were “entangled” in such a way that the behavior of one altered the behavior of the other. Whatever change one underwent, the other did, too.

The cat shape is a nod to Austrian physicist Erwin Schrödinger, who in 1935, came up with a mind-bending thought experiment to demonstrate the bizarre behavior of very, very, very, tiny particles inside and around atoms.

Schrodinger's cat, in the box.
Schrodinger’s cat, in the box.

A cat, a glass flask of poison, a soupçon of a radioactive substance, and a Geiger counter (a device for measuring radioactivity) are placed in a sealed box. If the instrument detects the hint of radioactivity, through a relay, it’d release a hammer, which would shatter the bottle, releasing the poison, thus, killing the cat.

The principle of “superposition,” a derivative of a model of quantum mechanics, proposed by Neils Bohr, asserts that an object can exist in all states, all at the same time, till we don’t attempt to know it.

The cat is simultaneously both alive and dead. It’s only when we open the box and take a peek inside that we learn whether it’s alive or dead. That is, it’s the very act of observation that affects its state.


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