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The Quandary Of Schrodinger's Cat

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Schrodinger's Cat -- The Beginning

As the study of quantum physics developed in the early 20th century, some of the bazaar discoveries triggered much head scratching. One of the most difficult to grasp features of the quantum world is that things appear to operate in probabilistic ways rather than in deterministic ways. In fact, speaking of the state of some quantum particle when not being observed proves to be meaningless.

Unlike a macro object, like a ball, quantum objects behave quite differently. You can put a ball on a table, go into another room, and assume correctly that the ball is sitting there all the while that you are away. Return, and you'll see the ball as you left it.

If you roll another ball at the first, you can predict quite precisely what will happen when the rolling ball hits the stationary ball, if you know their respective masses, the velocity of the rolling ball, and the angle of collision.

The Nature Of Quantum Weirdness


Schrodingers Cat Limerick

But the quantum world seems to be a kind of shadow world, with things not specifically in one state or another until they are observed. If a ball behaved in the quantum way, you'd have no idea what state the ball would be in once you left the room, and would not know what state it would be in when you returned.

Well, that's overstating it a bit. It's not that you could have no idea, but you could only compute a distribution of possibilities, and the ball may be in anyone of them when next observed. If you had such a quantum ball and performed the experiment thousands of times, you'd be able to see that the observed states matched up in frequency with the predicted probabilities.

So in the weird quantum world, one doesn't compute the next state of a particle, for instance. Instead one computes the next distribution of probabilities, and will witness one of those possible outcomes when making an observation. It's like things exist in a dream world in all possible states at the same time, and only settle on one when an observation is made.

Erwin Schrodinger was an early pioneer in the development of quantum physics, and he developed what's known as the Schrodinger Wave Equation as a way of managing these quantum probabilities. With the equation, an object's wave function could be calculated, which has since been interpreted as a distribution of possible states. Everything has a wave function, but the weirdness only seems to crop up in the atomic world.

Enter Schrodinger's Cat

In an effort to help conceptualize the strange quantum world, Schrodinger introduced a thought experiment called Schrodinger's Cat. In this experiment, Schrodinger designed a thought experiment that placed a familiar macro-world cat in a position that put its existence into a quantum situation.

As the experiment goes, the cat is placed in a box with a vial of poison. The vial is setup so that it will be broken, releasing the poison, if and when some quantum event occurs. Of course, the release of the poison would kill the cat.

But the quantum process that will trigger the release of the poison has no specific state of existence, being in a sense in all possible states at once. One cannot compute when the quantum event might take place, only compute the distribution of possibilities.

Since the cat is in the box, and its fate is now part of the quasi-state of the quantum process, its existence is also in a quasi-state. The math that must be used to compute the cat's fate is that which computes the quantum process. So it suggests that while in the box and unseen, the cat's state of existence is that of being both alive and dead, with some probability function being the only quantitative statement that can be made. Schrodinger referred to this coupling of the cat's state of existence and the quasi-state of the quantum process as entanglement, meaning that the cat's wave function and the quantum process wave function are entangled.

It turns out that all objects have a wave equation description, but it degenerates to a classical physics description for macro objects. However, when the cat is in the box with a quantum process, the wave functions for the cat and the quantum process become entangled, and must be solved together.


My Schrodinger's Cat Limerick

The Schrodinger's cat thought experiment is introduced to all students of physics at some point, and is also oft lampooned because of its confusing implications. Just for fun, I've put the enigmatic story of Schrodinger's cat into a witty limerick, as follows:


Said Schrodinger's Cat With A Smile
I'll Be In The Box With A Vial.
With The Poison I'll Be
Quantum Tangled You See,
Thus Alive And Dead Both All The While.

I put a Schrodinger's Cat theme on a couple of different t-shirt designs with some illustrations. You can get either design on a wide variety of t-shirts or sweatshirts, or on coffee mug by clicking you the respective image.


Schrodingers Cat Limerick


Schrodingers Cat Box T-shirt

But The Tale Doesn't End There

One of the uncomfortable interpretations of quantum strangeness is that somehow existence depends upon we humans observing it; that without some intelligence making an observation, it would seem that a specific quantum state doesn't exist, or as a physicist would say, the wave function doesn't collapse.

Immediately some began to ask the obvious question, "What if a camera or some recording device was there to watch the state of a quantum process? Would that make the wave function collapse?"

To treat this idea, another physicist by the name of Eugene Wigner proposed another thought experiment, known as Wigner's Friend. In this thought experiment, Wigner's friend is placed in a room to watch over the Schrodinger's cat experiment, while Wigner goes elsewhere. Wigner goes on to explain that once out of the room, all that happens is that his friend also has his wave function entangled with the quantum process that controls the fate of the cat.

The math would thus suggest that when Wigner is outside the room, the solution for inside the room is his friend simultaneously existing in all possible states, such as both witnessing a live cat and a dead cat. When Wigner opens the door, the composite wave function would collapse, yielding his friend reporting on the now determined state of the cat.

Sound confusing? Albert Einstein and Niels Bohr went round and round on these weird predictions, with Bohr seemingly winning them all.

Maybe this will help or maybe this will only add to the confusing, but the limerick I wrote about the Wigner's friend experiment will at least add some humor to the quandary.

My Wigner's Friend Limerick

With pen in hand and tongue in cheek, I put together this clever limerick to describe the Wigner's friend thought experiment:

Said Wigner About His Friend Lyle,
He Sat With The Cat All The While.
But Entanglement Came
For Him Just The Same
As The Cat In The Box With The Vial


Wigners Friend Limerick

Again, by clicking on the image you can purchase the design on a wide variety of light and dark colored t-shirts and sweatshirts, as well as on a coffee mug. Notice that the image of the cat appears like a multiple exposure, suggesting the quasi-state of the cat. I took poetic license in my limerick to give the hypothetical friend the name Lyle.