# What is the Opposite of Superposition?

## Recommended Posts

A few years ago one of my nieces, then aged twelve, asked me what "the opposite of superposition" is. Her question completely stumped me at the time. It still does. I have since considered placeholder answers like: normal position, position, classical position, etc. None of them seem satisfactory, however. This same question (with full quotation marks) also continues to stump Google.

NB. I am prepared to be told that the question is nonsensical - that it'll be like asking what the opposite of Spain is, for example. Still, I'm up for it.

Edited by GeeKay
##### Share on other sites

10 minutes ago, GeeKay said:

A few years ago one of my nieces, then aged twelve, asked me what "the opposite of superposition" is. Her question completely stumped me at the time. It still does. I have since considered placeholder answers like: normal position, position, classical position, etc. None of them seem satisfactory, however. This same question (with full quotation marks) also continues to stump Google.

NB. I am prepared to be told that the question is nonsensical - that it'll be like asking what the opposite of Spain is, for example. Still, I'm up for it.

Partition

##### Share on other sites

Why not separated.
Or excluded ?

Personally, I've always thought you either have superposition, or you don't.
There is no actual 'opposite'.

##### Share on other sites

I agree with MigL. It’s not something that has an opposite, as such. You’re either in one eigenstate, or in a superposition of them. (or in a situation where the concept doesn’t apply)

##### Share on other sites

I think it rather depends upon what you mean by superposition.

Physics uses the term is a different way from mathematics as it introduces the idea of 'interaction' or if you prefer 'combined action'.

So two sound waves from two separate sources in the same room (superposed) will interact to produce one single mathematically describable wave.

But two light waves from separate sources will not.

##### Share on other sites

7 hours ago, GeeKay said:

that it'll be like asking what the opposite of Spain is, for example. Still, I'm up for it.

That one's easy. The opposite of Spain is Switzerland!

I'm with @MigL on this one too. I would think that the opposite of having superposition is not having superposition.

##### Share on other sites

I'm with Joigus on this one.
I've been to Swtzerland; didn't like it much.
I think I would prefer Spain.

##### Share on other sites

It could be that the use of the adjectival 'super' in superposition has been confusing me. If measurement is the key that defines whether a quantum system is in superposition or not, then what about measured versus unmeasured?

Personally I suspect the opposite of Spain is located somewhere in the South Pacific. . .

##### Share on other sites

2 hours ago, GeeKay said:

It could be that the use of the adjectival 'super' in superposition has been confusing me. If measurement is the key that defines whether a quantum system is in superposition or not, then what about measured versus unmeasured?

Personally I suspect the opposite of Spain is located somewhere in the South Pacific. . .

Yes something (for 12 year olds) eg a system (for you) is in superposition or it is not.

If it is not in superposition it does not mean that that not being in superposition is the opposite of 'supersition'.

'The state of not being in superposition'  is the opposite of 'the state of being in superposition. '

However 'superposition' by itself is also a process; the process of supersition can be illustrated by the following examples.

A single frequency sine wave cannot be in superposition or not in superposition since there is only one of them.

We can construct a waveform by adding together different sine waves which are said to be 'put in superposition'

We can also deconstruct the same waveform into the component sine waves, a process that is the direct opposite of the construction.

Another example might be the mixing of two gases, say oxygen and nitrogen.

Individually each gas exerts a pressure, known as the partial pressure,
When these two gases are mixed, they are placed in a form of superposition, the mixture now possessing a new partial pressure which is the sum of the original two partial pressures.
Equally such a mixture may be separted out of superposition into two separate gases, each with its own original pressure.

However simply placing two objects into the same space or container, (this is the literal derivation of super-position = to position over) does not necessarily place them into superposition.
Something new has to result from this placement   for superposition to occur in Physics.

For example placing a red block and a blue block into a box does not place the blocks into superposition, although they both occupy the box.

2 hours ago, GeeKay said:

It could be that the use of the adjectival 'super' in superposition has been confusing me

Edited by studiot
##### Share on other sites

21 hours ago, studiot said:

Yes, I think I begin to get it now. Thanks, studiot, for your detailed and helpful explanations. Food for thought, indeed.

G

##### Share on other sites

2 hours ago, GeeKay said:

Yes, I think I begin to get it now. Thanks, studiot, for your detailed and helpful explanations. Food for thought, indeed.

G

🙄

Superposition has been extremely successful as a method in a wide range of Sciences and Mathematics.

Classically 'The Method of Superposition' is to be found in structural engineering, electrical engineering, Zoology and biology, optical engineering, mathematics (differential equations to name a few.

So it was quite natural to extend the method to quantum mechanics in the study of chemical bonding.
Pretty well all classical applications use what is known as linear superposition.
This means that the various parts of the superposition can just be added together (each perhaps modified by a single constant)

In fact they actually involve the opposite of superposition ie decomposition into the individual forces, curents, voltages, images etc and the effects of each calculated individually, before recombining them to solve the system

The first use of quantum superposition was called the linear combination of atomic orbitals (LCAO) method to describe what happens to the orbitals when two atoms bond together chemically.

This is where the subject introduces a joker because the pair of electrons become quantum entangled as they obey the Pauli exclusion principle.

Superposition should not be confused with entanglement.

Indeed the blue block and the red block I referred to earlier as not in superposition in their box are also entangled (this time classically) since if you remove one you atomatically know which one is left in the box. But remember they were never in superposition.

The most modern studies are conducted into non linear superposition, which is a much more difficult subject, that needs full mathematical rigour to progress.

There is only one nonlinear differential equation  - the Riccati Equation - for which superposition solutions are known.

Here is a paper from guys at CERN describing its application to Quantum Theory

If you want an expanded explanation of any of this, just ask.

Edited by studiot

## Create an account

Register a new account