- #1
David Byrden
- 90
- 8
I can never understand why students of QM speak about "simultaneous measurement" or "collapse of the wave function".
We all know that you can pick any relativistic reference frame from which to observe an experiment, so what's "simultaneous" to one observer may not be "simultaneous" to another.
It's easy to imagine an experiment where entangled particles A and B are measured "simultaneously" for me, "A before B" for you in a passing spaceship, and "B before A" for someone going the other way. The results must be the same; that's a constraint that could be useful in our analyses; so why do we pretend it doesn't exist?
As for "collapse of the wave function", this troublesome notion simply fades away if you stop thinking that the future hasn't happened yet.
We all know that we're embedded in spacetime, so why not lay out a quantum interaction on a space-time surface? There is no "collapse" then. The events that happen to the particle - its emission at one point in spacetime, its detection at another - are constraints on its wave equation.
Our everyday notion that the future "hasn't happened yet" leads us to imagine that the end of the particle's journey hasn't happened yet, and that's why we imagine the wave function spreading out; and that's why its "collapse" confuses us.
If you take yourself "out of time" and imagine that the detection of the particle in the future is as real as its emission in the past, then there's no collapse to explain.
Sorry if I rant a bit.
Anyway, that leads to a question. Based on what I just said, I expect that quantum teleportation is not only superluminal, but it travels backwards in time.
I expect that you can measure the teleported state well in advance of the moment when you make the Bell measurement on the particle whose state you want to teleport. In fact, I expect that you can measure the teleported state immediately after the creation of the entangled pair.
That may sound like seeing into the future, or sending information back into the past; but I believe you can't set up a "time paradox" because you don't have the two classical bits that will result later from the Bell measurement.
Question: has anybody tested this arrangement experimentally?
I'm new to QM and I apologise if I'm asking something obvious. Please enlighten me.
David
We all know that you can pick any relativistic reference frame from which to observe an experiment, so what's "simultaneous" to one observer may not be "simultaneous" to another.
It's easy to imagine an experiment where entangled particles A and B are measured "simultaneously" for me, "A before B" for you in a passing spaceship, and "B before A" for someone going the other way. The results must be the same; that's a constraint that could be useful in our analyses; so why do we pretend it doesn't exist?
As for "collapse of the wave function", this troublesome notion simply fades away if you stop thinking that the future hasn't happened yet.
We all know that we're embedded in spacetime, so why not lay out a quantum interaction on a space-time surface? There is no "collapse" then. The events that happen to the particle - its emission at one point in spacetime, its detection at another - are constraints on its wave equation.
Our everyday notion that the future "hasn't happened yet" leads us to imagine that the end of the particle's journey hasn't happened yet, and that's why we imagine the wave function spreading out; and that's why its "collapse" confuses us.
If you take yourself "out of time" and imagine that the detection of the particle in the future is as real as its emission in the past, then there's no collapse to explain.
Sorry if I rant a bit.
Anyway, that leads to a question. Based on what I just said, I expect that quantum teleportation is not only superluminal, but it travels backwards in time.
I expect that you can measure the teleported state well in advance of the moment when you make the Bell measurement on the particle whose state you want to teleport. In fact, I expect that you can measure the teleported state immediately after the creation of the entangled pair.
That may sound like seeing into the future, or sending information back into the past; but I believe you can't set up a "time paradox" because you don't have the two classical bits that will result later from the Bell measurement.
Question: has anybody tested this arrangement experimentally?
I'm new to QM and I apologise if I'm asking something obvious. Please enlighten me.
David