Experiment shows that two observers experience different realities

In 1961, Eugene Wigner outlined an experiment that illustrated how two observers might experience different realities. In the paradox called superposition, a system contains all possible states at the same time; however, once the system is observed or measured, it commits to a definite state.

Last week, MIT Technology Review reported a test of Wigner’s thought experiment (registration wall) where researchers created different realities and compared them. Researchers concluded that realities “can be made irreconcilable” which makes it “impossible to agree on objective facts about an experiment.”

The researchers used entangled photons to create two alternate realities with two observers—one represented Wigner and one represented Wigner’s friend.

Wigner’s friend measures the polarization of a photon and stores the result. Wigner then performs an interference measurement to determine if the measurement and the photon are in a superposition.

The experiment produces an unambiguous result. It turns out that both realities can coexist even though they produce irreconcilable outcomes, just as Wigner predicted.

This experiment suggests that objective reality does not exist, calling into question the western concept of the scientific method.

The superposition backstory

You may be familiar with an example of superposition which was validated in 2016 that involves firing photons at two parallel slits in a barrier:

One fundamental aspect of quantum mechanics is that tiny particles can behave like waves, so that those passing through one slit “interfere” with those going through the other, their wavy ripples either boosting or canceling one another to create a characteristic pattern on a detector screen. The odd thing, though, is this interference occurs even if only one particle is fired at a time. The particle seems somehow to pass through both slits at once, interfering with itself. That’s a superposition.

In 2017, researchers in Israel and Japan proposed an experiment to further test this phenomenon by allowing researchers to “say with certainty something about the location of a particle in a superposition at a series of different points in time—before any actual measurement has been made.”

Schrödinger’s cat

A related concept that has entered popular culture through science fiction stories, TV and film is the paradox known as “Schrödinger’s cat”. In 1935, the Austrian physicist Erwin Schrödinger created his famous thought experiment: place a cat in a sealed box where its life or death depends on the state of a sub-atomic particle. In this thought experiment, the cat is both dead and alive at the same time until someone opens the box (observation).

Schrödinger sought to illustrate the challenge of microscopic level superposition on what we humans observe at the macroscopic level. Although Schrödinger accepted that superposition exists he rejected its application to the living world: a cat cannot simultaneously be both dead and alive. He questioned when the resolution of all possibilities occurs.

Schrödinger’s kittens

Last year, researchers demonstrated that “quantum mechanics is not just the physics of the extremely small.”

“Schrödinger’s kittens,” loosely speaking, are objects pitched midway in size between the atomic scale, which quantum mechanics was originally developed to describe, and the cat that Erwin Schrödinger famously invoked to highlight the apparent absurdity of what that theory appeared to imply. These systems are “mesoscopic” — perhaps around the size of viruses or bacteria, composed of many thousands or even billions of atoms, and thus much larger than the typical scales at which counterintuitive quantum-mechanical properties usually appear. They are designed to probe the question: How big can you get while still preserving those quantum properties?

To judge by the latest results, the answer is: pretty darn big.

Schrödinger was exploring the world of quantum mechanics; however, we know that in the “real world” two people may not interpret a shared experience the same way. Psychological research shows that our perception of reality is subjective; it is not a direct representation of a shared objective reality.

Often we assume that everyone sees the world the same way we do, that there is an objective reality (called naive realism). In other words, we want to believe in rationality, that anyone observing or experiencing the same situation would describe or characterize the event in the same way we do.

Even when we are aware that there is a subjective component to our assessment of a situation, rarely are we “aware of the degree to which … corrective efforts fall short; people consequently infer that their judgments are more accurate, objective, and realistic than they really are.”

Lesson from hard and soft science: the world is more gray than black-and-white.

Size and complexity do not matter?

In this latest experiment, the researchers challenge Schrödinger’s objection:

Since quantum theory does not distinguish between information recorded in a microscopic system (such as our photonic memory) and in a macroscopic system the conclusions are the same for both: the measurement records are in conflict regardless of the size or complexity of the observer that records them.

You can read the latest research paper, Experimental rejection of observer-independence in the quantum world, at the open access eprint database arXiv hosted at Cornell University.

Featured image: PixaBay