The Shocking Truth About Schrodinger’s Cat

The Shocking Truth About Schrodinger’s Cat

Another idea which changed my perspective, and this one still haunts me. It’s split across two different sources which I read in succession. Furthermore, because it pertains to quantum mechanics, it’s going to take me a little while, and two excerpts, to explain.

The first is from Neal Stephenson and Nicole Galland’s The Rise and Fall of D.O.D.O.. Stephenson is possibly my favourite author, but this is not his strongest book. That said: even a weak Stephenson book[1] is worth more of your time than a strong book from most other authors, in my opinion. This one is about quantum mechanics[2], and here is its explanation of Schrodinger’s Cat:

“You put a cat in a sealed box. There’s a device inside of the box that is capable of killing the cat, by breaking open a vial of poison gas or something. That device is triggered by some random event generator, like a sample of some radioactive material that either decays—producing a bit of radiation—or doesn’t. You close the lid. The cat and the poison gas and the radioactive sample become a sealed system—you cannot predict or know what has happened.”

“You don’t know if the cat is alive or dead,” I said.

“It’s not just that you don’t. You can’t. There is literally no way of knowing,” Tristan said. “Now, in a classical physics way of thinking, it’s either one or the other. The cat is either alive or dead for real. You just don’t happen to know which. But in a quantum physics way of thinking, the cat really is both alive and dead. It exists in two mutually incompatible states at the same time. Not until you open the lid and look inside does the wave function collapse.”

“Whoa, whoa, you had me until the very end!” I protested. “When did we start talking about—what did you call it? A wave function? And how does that—whatever it is—collapse?”

My bad,” he said. “It’s just physicist lingo for what I was saying. If you were to express the Schrödinger’s cat experiment mathematically, you’d write down an equation that is called a wave function. That function has multiple terms that are superimposed—it’s not just one thing.”

“Multiple terms,” I repeated bleakly.

“Yeah. A term here means a fragment of math—it is to an equation what a phrase is to a sentence.”

“So you’re saying there is one term for ‘cat is alive’ and another for ‘cat is dead’? Is that what you mean in this usage?”

“Yes, O linguist.”

“And when you say they are superimposed—”

“Mathematically it just means that they are sort of added to each other to make a combined picture of the system.”

“Until it ‘collapses’ or whatever.”

He nodded. “Multiple terms superimposed is a quantum thing. It is the essence of quantum mechanics. But there is this interesting fact, which is that that kind of math only works—it only provides an accurate description of the system—until you open the lid and look inside. At that point, you see a live cat or a dead cat. Period. It has become a classical system.”

As I said, it’s not the strongest Stephenson book, but it did set me to thinking more about quantum mechanics. From there I started thinking about quantum computers, and I happened across David Kemp’s An Interactive Introduction to Quantum Computing.

Now, with that in mind, here is a further explanation of quantum states from Part 2:

Describing quantum computing in terms of superpositions of states that “collapse” to the observed state upon “measurement” is a very conventional approach to explaining the physics behind quantum computing. However, there are some serious deficiencies with this approach.

Probably the most fundamental problem is: What is so special about measurement that it causes quantum superpositions to collapse?

The measuring equipment itself is made of the same stuff as the qubits being measured (protons, neutrons, electrons, and photons).

When measuring a qubit that is in a superposition of two different states, there is nothing in quantum physics that says why the measuring equipment might cause the superposition to collapse to a single state instead of the measuring equipment becoming entangled with the qubit. Instead of the quantum state collapsing, the result could be a superposition of the following two states:

  1. the qubit being 0 and the measuring equipment detecting 0;

  2. the qubit being 1 and the measuring equipment detecting 1.

If you consider your conscious awareness to be nothing more than patterns of activity in your brain, and that your brain is governed by the laws of physics, then there is nothing in quantum physics that says why, when you look at the measurement outcome, you yourself do not become entangled with the quantum qubit and the measuring equipment. The result would be a superposition of the following two states:

  1. the qubit being 0, the measuring equipment detecting 0, and you being conscious of the measurement being 0;

  2. the qubit being 1, the measuring equipment detecting 1, and you being conscious of the measurement being 1.

Think of it as two alternative realities existing. In one reality you see a 0, and in the other you see a 1. Quantum interference is the only ways that these realities interact.

Putting it all together: when you open the box and look inside, the waveform doesn’t collapse, as the popular explanation would have it. Instead, you become part of the waveform. The cat is still both alive and dead. You are an observer of a live cat and, simultaneously, an observer of a dead one. You’ve become Schrodinger’s observer of cats. But you’re only aware of one of those realities. So who or what is the other you?


  1. I don’t want to diminish Galland’s role here, but this is the only of her books I’ve read so I’m unable to make a comparison. ↩︎

  2. Also: time travel and parallel universes. More specifically: the idea that witches were women who could manipulate quantum mechanics. ↩︎