Emma_Acid is correct.

But...

khol, on 24 November 2013 - 06:16 PM, said:

to all you physicists out there

whats the final consensus on this experiment

Since you asked...

Every system exists in a single, specific state at all times. However this state does

*not* need to be specific for any arbitrary basis set. When you perform a measurement, the very act of measuring the system corresponds to a sudden (and, in the limit of a perfect measurement, a discontinuously sudden) change in that system's environment such that the only

*stable* state a system can be in is one of the basis states for that measurement.

Wave/particle duality is the most famous example of this. When a system is in empty space, the

*natural* state for this system to be in is a plane wave. The true, singular state of the system

*could* be expressed as a superposition of plane waves, but as long as the system is in empty space this superposition will be unstable - random fluctuations will eventually collapse the system to a singular plane wave state.

If you attempt to measure the linear momentum of a singular plane wave state you will get a specific answer 100% of the time. If you attempt to measure the linear momentum of a superposition of plane wave states, the very act of measuring will collapse the system to a singular plane wave state (i.e. only one of the plane waves involved in the superposition will be ``selected''). Subsequent measurements of momentum will reveal the exact same linear momentum 100% of the time.

Every wave state can also be expressed as a superposition of particle states. This is just a mathematical trick - it is irrelevant until we attempt to measure the position of the system.

How do we measure the position of something? We set up a confined box and then check if the system is inside it (the smaller the box, the more precise our measurement). But we can't do this without changing the environment - in other words, we no longer have empty space. It is this change, this abrupt attempt to confine the system, that causes the system to collapse into a position state (or a superposition of smaller number of position states, if our position measurement was somewhat vague).

Once we remove the box, and return to empty space, the system will start to ``spread out'' and gradually evolve back into a plane wave state.

There is a lot of fuss made over wave/particle duality because ordinary people can grasp the meaning of ``waves'' and ``particles''. But waves and particles are just two of an infinite number of possible ``basis sets'' for a system.

Two other classic quantum mechanical systems are the

quantum harmonic oscillator and the

orbitals of a hydrogen atom. Neither of these two sets of solutions are plane waves or particles, and in fact we could perfectly legitimately describe every plane wave as a superposition of quantum harmonic oscillator states, or every hydrogen atom orbitals.

The ``natural'' state of a system is an

*eigenfunction of the system's Hamiltonian*. If the quantity you want to measure is an

*eigenvalue* of these states, then your measurement will not affect the system (i.e. a momentum measurement on a system in empty space, a position measurement on a system in an infinitely deep and infinitesimally narrow potential well, an ``excitation number'' measurement on a quantum harmonic oscillator, or an angular momentum measurement on a hydrogen atom orbital).