# Quantum Superposition While Observing Phenomena?

• I
• DQuantum14
In summary: If you open the boxes at the same time, the cats will be both alive and both dead, but if you open them at different times, the cats will be in a superposition of alive and dead.In summary, the Schrodingers Cat paradox shows that it is impossible for a cat to be in a superposition of alive and dead.

#### DQuantum14

I decided to perform a little thought experiment -- without the mathematics.
Assume we have two Schrodingers' Cats. After a while, they will be in a superposition of being alive and dead at the same time. Now assume that they are entangled, and we open the boxes at the exact same time.
Cases:
Cat 1 and 2 are alive
Cat 1 and 2 are dead
Cat 1 is alive, 2 is dead
Cat 1 is dead, 2 is alive

However, as they are entangled, the opposite must happen to the other cat, so the two cats cannot be both alive and dead at the same time -- or can they? Since you are opening the two boxes, or measuring the states of the cats at the exact same time, aren't all of these cases possible? If they are both dead, let's say, they also both must be alive at the same time, due to their entanglement. Therefore, even after measuring the states of the cats, there is a superposition happening.

Now assume there are two entangled particles, with a clockwise and counterclockwise spin at the same time. If both particles' states are measured at the same time, will the particles be in a superposition even after measurement due to entanglement?

I have heard that entanglement is an instantaneous process, but assuming both boxes are opened/both particles are measured at the same time, will a second superposition occur?

I decided to perform a little thought experiment -- without the mathematics.
Assume we have two Schrodingers' Cats. After a while, they will be in a superposition of being alive and dead at the same time. Now assume that they are entangled, and we open the boxes at the exact same time.
Cases:
Cat 1 and 2 are alive
Cat 1 and 2 are dead
Cat 1 is alive, 2 is dead
Cat 1 is dead, 2 is alive
... these last options describe 4 states that are only available if the overall state is not an entangled state, so you have written a contradiction.
The entangled state you are thinking of is a superposition of the third and fourth ones.
Think of the word "entangled" is a technical term that describes a class of total state ... sometimes used loosely to say that the individual states are not independent.

It does not matter which order the cat states are measured or if the measurement is simultaneous...
(note: it is always possible to find a reference frame where the measurements are simultaneous... the probabilities must still hold.)

Nice clear lecture on the basics of entangled states
http://www.lecture-notes.co.uk/susskind/quantum-entanglements/lecture-5/example-states/
- the notation |x,y> is just a state so |u,d> is a 2-particle state where the 1st one is spin-up and the second one is spin-down. The 4 independent cat states would be |aa>, |ad>, |da>, |dd>... much of the maths can be skimmed: just assume he did it right.

The main point of the schrodinger cat experiment is to link the fates of the cats to a quantum system ... where the cat's fate is tied to a measurement of the system.
Try this for an entangled particle system.

I see.. thanks!

DQuantum14 said:
After a while, they will be in a superposition of being alive and dead at the same time.

A cat can never, ever be in a superposition of alive and dead. Its utterly impossible as cats are classical objects with definite position. The positions of the constituent parts of alive and dead cats are totally different eg the lungs and heart of an alive cat moves, but a dead cat doesn't.

Thanks
Bill

... which is, of course, the point of the Schrodingers Cat paradox: linking a QM system with a classical, macroscopic, one, and asking questions about the nature of measurement etc. The proposed mod would be to put two cats in boxes with entangled QM systems.

bhobba

## 1. What is quantum superposition?

Quantum superposition is a fundamental principle in quantum mechanics that describes the ability of a particle to exist in multiple states or positions simultaneously.

## 2. How does quantum superposition apply to observing phenomena?

When observing phenomena at the quantum level, particles can exist in a state of superposition, meaning they are in multiple states at once. This allows for the observation of multiple outcomes or possibilities simultaneously.

## 3. Why is quantum superposition important in understanding the behavior of particles?

Quantum superposition is important because it allows for the understanding of the dual nature of particles, which can behave as both particles and waves. It also plays a crucial role in quantum computing and communication.

## 4. Can we observe quantum superposition directly?

No, quantum superposition cannot be directly observed. This is because observation or measurement of a particle causes it to collapse into a specific state, resulting in the loss of the superposition.

## 5. How is quantum superposition related to the uncertainty principle?

The uncertainty principle states that the more precisely we know the position of a particle, the less we know about its momentum, and vice versa. Quantum superposition allows for the simultaneous existence of multiple states or positions, which leads to uncertainty in measurement.