The Schrödinger's Cat Experiment In Quantum Mechanics 2

The Schrödinger’s Cat Experiment In Quantum Mechanics

The quantum world is unpredictable. The behavior of a quantum particle is perplexing. Where Einstein’s photoelectric effect pointed out at the particle nature of a light wave, the Davisson-Germer experiment, on the other hand, demonstrated the wave nature of an electron. It’s just like the quantum particles are suffering from a split personality disorder!

Wave-particle duality
Image Courtesy:
Wave-particle duality
Image Courtesy:

Quantum mechanics cannot easily be reconciled with everyday language and observations, and hence, it has often seemed absurd to physicists as well. So, ever since the notion of “Quantum  Physics” came into existence, people all over the world have come up with a number of interpretations to explain that how things actually work in the eerie quantum world. However, for the better part of the last century, the most accepted explanation for why the same quantum particle may behave in different ways was given by the Copenhagen interpretation. So first of all, let’s try to understand what Copenhagen Interpretation actually says!

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Copenhagen Interpretation :

Werner Heisenberg (left) with Niels Bohr at a Conference in Copenhagen in 1934. Photo: Fermilab, U.S. Department of Energy
Werner Heisenberg (left) with Niels Bohr at a Conference in Copenhagen in 1934.
Photo: Fermilab, U.S. Department of Energy

The Copenhagen Interpretation of quantum mechanics was largely devised from 1925 to 1927 by Niels Bohr and Werner Heisenberg. It is one of the oldest proposed interpretations of quantum mechanics, and still remains one of the most commonly followed. According to this interpretation, physical systems do not possess definite properties prior to being measured. And, quantum mechanics can only predict the probability distribution of a given measurement’s possible results.

In other words, measurement affects the system, causing it to reduce to only one of the possible values immediately after the measurement. Confused? It’s normal to baffle at this point, because, this is not what we observe in our daily life scenario. Well, this is where Schrödinger came up with his famous cat experiment to point out a flaw in the Copenhagen interpretation of superposition!

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Erwin Schrodinger
Image Courtesy :Wikipedia
Erwin Schrodinger
Image Courtesy :Wikipedia

Aim of Schrödinger’s Cat Experiment:

Before we begin with this, let me make one thing very clear to you. The Schrödinger’s cat experiment was not a real activity carried out in any lab, rather it was a thought experiment, that was devised by Austrian physicist Erwin Schrödinger in 1935, though the idea originated from Albert Einstein. Schrödinger designed it to show what the Copenhagen interpretation would look like if the mathematical terminology used to explain superposition in the microscopic world was replaced by macroscopic terms that an average person could visualize and understand. 

The Cat Is Both Dead And Alive:

In this famous thought experiment, a cat is placed in a steel box along with a Geiger counter, a vial of poison, a hammer, and a radioactive substance as shown below. When the radioactive substance decays, the Geiger counter detects it and then triggers the hammer to release the poison, which subsequently kills the cat. But, radioactive decay is a random process, and there is no way to predict when will it happen. So, the atom kind of exists in a state of superposition—both decayed and not decayed at the same time.

Pictorial description of Schrodinger's cat experiment
Image courtesy: wikipedia
A pictorial description of Schrodinger’s cat experiment


Until the box is opened and an observation is made, an observer doesn’t know whether the cat is alive or dead. This is because the cat’s fate is tied to whether or not the atom has decayed. So, as Schrödinger put it,  the cat is “living and dead … in equal parts” until it is observed. This is the Schrödinger’s cat experiment! But, what does it signify?

Inferences From Schrödinger’s Cat Experiment :

As we have read earlier, the cat ends up being both dead and alive at the same time. But, the existence of a cat that is both dead and alive at the same time is quite absurd and does not happen in the real world. Right? So, this thought experiment showed that collapse of all possible outcomes to merely one outcome is not just driven by conscious observers or measurements, there is something more to the collapses. Every interaction that quantum particle makes can collapse its state.

This means that as soon as the radioactive atom will interact with the Geiger counter, it will collapse from its non-decayed/decayed state into one definite state. The Geiger counter will either get definitely triggered and the Cat would die, or the Geiger counter wouldn’t get triggered at all and the cat won’t die. But both won’t happen simultaneously. So, quantum state collapse is not driven just by conscious observers/ measurements, and “Schrodinger’s Cat” was just a teaching tool invented by Schrödinger to make this fact more obvious and simpler to grasp.

More in quantum world:

Undoubtedly, the role of the observer and measurements remains an important question in the study of quantum physics and is an endless source of speculations, especially in the field of quantum computation. Still, throughout the years, the  Schrödinger’s cat analogy has been one of the best analogies used to illustrate the emerging theories of how quantum mechanics works.

Also watch: What is Quantum Mechanics, Exactly?

24 thoughts on “The Schrödinger’s Cat Experiment In Quantum Mechanics”

  1. “Split personality disorder”
    I think it’s the best way to represent wave particles duality ???

  2. Nature only appears that way because our biological senses interpret those spectrums of energy as the way objects should appear. Otherwise, without our pre-programmed interpretation, we would end up perceiving a wave of energies swirling around us. Nothing actually collapses. I am just joking.

  3. Observation by scientists and others is a process whereby light enters the eye and is encoded into perception by the brain which then makes the information available to us as thought. Kind of a crude way Of putting that but you understand what I mean. We could be anywhere at any time making our observation but we are not necessarily the only one making the observation. If 10 people make the observation in succession then the question is has the system collapsed 10 times in that sequence of observation? The thought is that we would shine a light into that system do understand what we’re looking at, and precipitate some change in the quantum state. But all of that sciency technique aside, Everything is in contact with everything else at all times, that is, We are Johnny-come-lately’s to any observation considering the length of time what we are observing has existed and the number of opportunities for random protons to bounce off of what we’re studying in the long history of light interacting with matter – just no one was there to Perceive the interaction and write it down.

    Maybe the big bang was not an expansion but a collapse, Like super cooled water freezes when a bottle of water kept in the freezer is disturbed and crystals can start to form. The freezing starts at one end and ice Crystals grow until the temperature of the water remaining in the bottle reaches 0 centigrade. so in a process unimaginable to our puny human minds the fabric of the universe coalesces from a super cooled plasma-miasma until nuclear nucleation starts and works its way along.

    But the point is, like the water molecules in the bottle, each one that can joins its neighbor in a growing ice crystal because it does not exist in a vacuum. Everything in the universe is also in contact with something else either physically, whatever that means, or is affected by electromagnetic-gravimetric radiation of some sort. So everything is ‘observed’ whether we were privy to it or not.

    Some animal activist actually believe the cat experiment was real and are still upset about it. So I guess existing in an isolating vacuum is possible.

  4. The schodinger experiment is clearer to me now. till now I could not figure how quantum mechanics to this simple experiment .

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