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When Wigner’s Friend Knocks, Don’t Answer

Secular media are touting a new experiment that seems to prove that objective reality doesn't exist

Recent reports in physics have declared that there is no objective reality. An article in Interesting Engineering summarizes the issue, covering work over the last several years in Science Advances (“Experimental test of local observer-independence”) and the MIT Technology Review (“A quantum experiment suggests there’s no such thing as objective reality”).

This is not a mere thought experiment, but an actual experiment. Researchers demonstrated that different observers can experience different facts when measuring entangled particles, thereby calling into question objective reality. If science depends on facts, they ask, and researchers can experience different facts, then how can we make sense of science? In the spirit of truth not contradicting truth, let’s examine the claims as Catholics in the light of faith. The question of objective reality reaches beyond physics and influences our culture.

Quantum paradoxes are theorems of physics that contradict common sense. Quantum theory began with a paradox by explaining that electrons exist in one energy level or another but not in between, which is inconsistent with macroscopic continuous experience of motion. Electrons seem to have discontinuous (quantized) motions, their movement associated with massless packets (quanta) of energy called photons. At the quantum level, the universe seems pixelated.

Another paradox is entanglement, the idea that subatomic particles exist in pairs or groups with complementary properties (spin, polarization). These pairs go together no matter how far apart the particles are, and an action on one particle can have instantaneous effects on the other particle elsewhere in the universe. Albert Einstein called this “spooky action at a distance.”

So what is the new paradox? It’s an expansion of an older paradox called the Wigner’s Friend paradox, devised by Nobel Prize-winner Eugene Wigner in 1961. Wigner’s work builds on yet another paradox, Erwin Schrödinger’s famous cat-in-the-box thought experiment from 1935. Let’s unpack that.

The Schrödinger’s cat demonstration goes like this: a cat is locked in a steel chamber for an hour, along with a radioactive substance and a Geiger counter, a hammer, and a vial of poison. If one atom of the substance decays—and there’s a fifty-fifty chance that it will—then the hammer will shatter a vial of cyanide, which will kill the cat. So for one hour, all we can express about the cat is that he’s in a “superposition” using a “wave function”—a state where life and death are smeared out in equal parts—and thus the cat is thought of as both alive and dead. Opening the box and observing the cat “collapses the wave function.” No cats were ever harmed; the point for Schrödinger, hypothetically, was to show that indeterminacy at the atomic level can be transferred to the macroscopic.

The Wigner’s Friend thought experiment replaces the cat in the box with a set of friends. One friend is in the laboratory measuring the state of a quantum particle; he’s in the box, so to speak. The other friend is an observer of the friend in the laboratory. The current theorem includes two pairs of friends and two laboratories, with one friend in each lab and the other outside, observing. Entangled particles are sent from a single source to each laboratory. The outside friends can only ask the inside friends about the outcomes of their measurements. So now we have conscious scientists in four places, two in labs and two outside, and a pair of entangled particles going to each. This leads to a situation where the scientists in the lab can measure a quantum state, whereas the observers outside will only know a smeared out, mixed state. Further, all four friends can experience different realities, since the observed state of the entangled particles is probabilistic.

The research team demonstrated this paradox using laser-generated entangled photons, particles that ought to have corresponding states even upon separation to the two labs. They measured them simultaneously with two sets of optics (as the labs). The optics detected different “facts,” just as the thought experiment predicted. That is the basis of the renewed discussion about whether quantum mechanics proves there is no objective reality.

Catholics should care about this because a cultural rejection of objective reality means that relativism takes hold. Imagine someone reading the pop science commentary and invoking this new quantum paradox to argue that nothing really matters in life anyway. With a relativistic mindset, anyone can define his own reality and therefore morality, a perception at the heart of so many social confusions. Kids think they can decide they are either sex, or any “gender” or even species they want. Marriage can mean anything. Natural law becomes “do whatever you want.” The U.S. culture is already heavily under the influence of relativism, and atheism is on the rise.

The article in Interesting Engineering, for example, concludes, “So the next time your friends think something is or isn’t the case, consider interjecting with an argument from quantum physics: they’re both wrong, and so are you, because even the simple fact of the disagreement itself is just another illusion.”

The MIT Technology Review uses more sophisticated language but says the same thing, essentially (although the author notes that scientists will look for loopholes with further testing). The author submits that these results call into question locality and freedom of choice. By locality is meant that different views still describe one real event, like when an insurance adjuster interviews different eyewitnesses to an auto crash. By freedom of choice is meant that we assume that someone making a test has the freedom to decide how to design it, but the new expanded Wigner’s Friend theorem suggests that he doesn’t. If the outside observer’s view depends on the insider’s test result, then the outside observer isn’t free.

The researchers themselves, however, used more tentative wording in their abstract: “If one holds fast to the assumptions of locality and free-choice, this result implies that quantum theory should be interpreted in an observer-dependent way.” Here they describe an adjustment only in how quantum theory is interpreted, not in the existence of objective reality overall.

I think we actually do have macroscopic examples of these paradoxes. Consider a pregnant couple who don’t want to know the sex of their child. For the duration of the pregnancy, everyone must assume a smeared, mixed state of probability. The baby could be either a boy or a girl. At birth, the so-called wave function collapses, but no one assumes before then that the child really exists in both states until birth.

It was the same for Schrödinger. With the cat-in-the-box paradox, he ultimately wanted to show that the mixed state is absurd as a reality. He considered the thought experiment a necessity to express such a state in the equations if no observation could be made. Potential is the better word: until a measurement can be made, the unknown state could potentially be two possibilities. Once we know what it is, we adjust our response. We alter the equations, or clean the cat box, or buy pink instead of blue.

Fr. Stanley L. Jaki, the physicist priest whose work I promote, said that interpretations of quantum physics suffer from confusion between the ontological and the operational. Indeterminacy in quantum theory should be taken to mean that we humans have limits on our ability to measure beyond a certain realm (operational), not that the fundamental particles of nature are absolutely random (ontological). We are human. The best scientists among us are limited in what they can know. Think about it: our inability to know something cannot be the explanation for it. (See my book Particles of Faith, Ch. 6.)

We do not need to reject objective reality because of this experiment. If someone stole your phone, would you pretend it didn’t really happen? If your pet died, would you say it didn’t? If we don’t understand everything about quantum physics, should we deny our own ability to design experiments and conceptualize theories? Of course not.

As Catholics, we acknowledge a spiritual realm as well as a physical realm, and that God created everything and holds everything in existence. We accept mystery as a reality, and we acknowledge that we fall short of omniscience. This healthy view of science allows us to always question and seek, because we are certain that truth will not contradict truth. After all, if the converse is true, then all the atheistic scientists are out of a job—because what’s the point?—and the only scientists left will be theists!


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