Tagged Questions
13
votes
2answers
134 views
Is every quantum measurement reducible to measurements of position and time?
I am currently studying Path Integrals and was unable to resolve the following problem. In the famous book Quantum Mechanics and Path Integrals, written by Feynman and Hibbs, it says (at the beginning ...
2
votes
2answers
154 views
How do we know that there isn't a classical solution to the measurement problem/Quantum Mechanical uncertainty?
It was mentioned to me that it can be shown that there is no classical explanation for the uncertainty in Quantum Mechanics -- i.e. that there are no hidden workings that we have just not yet seen, ...
0
votes
1answer
63 views
Is the time of collapse of the wave function empirical?
Is the time of the collapse of the wave function empirical?
Suppose there is a very long von Neumann chain of observations of a quantum system. Suppose also practically irreversible decoherence ...
3
votes
1answer
173 views
If nothing is “objectively real” prior to “measurement”, what exactly is a “measurement”?
If nothing is "objectively real" prior to "measurement", what exactly is a "measurement"?
Is there any "objective" criteria to demarcate a process as being a "measurement" or not? If "measurements" ...
0
votes
1answer
129 views
Who are “we”, and what counts as a “question” in consistent histories?
If the preferred basis in quantum mechanics and/or choice of consistent histories in consistent histories is arbitrary, and can only be determined by the "questions we ask", just who exactly is this ...
2
votes
0answers
59 views
How to explain Tsirelson's inequality using extended probabilities?
How to explain Tsirelson's inequality using extended probabilities?
Some people have tried explaining the Bell inequalities using extended probabilities.
For instance, a pair of entangled photons ...
5
votes
6answers
625 views
What constitutes an observation/measurement in QM?
Fundamental notions of QM have to do with observation, a major example being The Uncertainty Principle.
What is the technical definition of an observation/measurement?
If I look at a QM system, it ...
1
vote
3answers
156 views
In Copenhagen, can this idea preserve locality for Bell inequalities?
Generate an entangled pair of qubits. Send to Alice and Bob far away from each other. Both measure along basis in one of two possible orientations. The result is sent to Charlie at some later time, ...
6
votes
3answers
241 views
What is the physical meaning of weak expectation values?
In the two-state formalism of Yakir Aharanov, the weak expectation value of an operator $A$ is $\frac{\langle \chi | A | \psi \rangle}{\langle \chi | \psi \rangle}$. This can have bizarre properties. ...
0
votes
1answer
119 views
The System and the Measuring Gadget
In Quantum Mechanics the value of an observable results from the interaction between the "system" with the "Measuring gadget".
But when the experimenter[or the technologist concerned] is ...
4
votes
2answers
144 views
What counts as a measurement?
In quantum mechanics, an elementary particle does not have a well defined position until a measurement is performed on it (right?). Such a "measurement" is any sort of interaction with other ...
7
votes
2answers
323 views
Is the collapse of the wave function inherently time asymmetric?
Schroedinger's equation, as we all know, is time symmetric. In quantum field theory, we have to come up with a more sophisticated CPT reversal, but the essential point remains unchanged. However, the ...
1
vote
0answers
29 views
Information conservation during quantum measurement in $\psi$-epistemic interpretations [duplicate]
Possible Duplicate:
Information conservation during quantum measurement
I asked a version of the following quesiton previously on Physics.stackexchange, where it didn't get a lot of ...
5
votes
3answers
309 views
Information conservation during quantum measurement
Consider the following experiment. I take a spin-$\frac{1}{2}$ particle and make a $\sigma_x$ measurement (measure the spin in the $x$ direction), then make a $\sigma_y$ measurement, then another ...
4
votes
5answers
382 views
How isolated must a system be for it's wave function to be considered not collapsed?
As an undergrad I was often confused over people's bafflement with Schodinger's cat thought experiment. It seemed obvious to me that the term "observation" referred to the Geiger counter, not the ...
-2
votes
1answer
248 views
Can God collapse the wavefunction? [closed]
This is a semi-theological question which I hope isn't out of place in this forum.
The Copenhagen interpretation requires observers to collapse the wavefunction. Certainly, the question of whether or ...
1
vote
0answers
69 views
Identifying fragments when there is a superposition of fragments in quantum Darwinism
In Zurek's theory of quantum Darwinism, information about the pointer states of a system imprint themselves upon fragments of the environment carrying records about the state of the system. ...
2
votes
6answers
350 views
Do we really know which slit the photon passed through in Afshar's experiment?
The plain old double slit experiment displays interference when we don't measure which slit the photon passed through, and no interference when it is measured. Let's turn our attention to the case ...
1
vote
1answer
78 views
Do interaction-free measurements require a physical collapse or splitting in order to be truly interaction free?
Interaction-free quantum experiments like Renninger's experiment or the Elitzur-Vaidman bomb tester are often taken to be examples of interaction-free measurements of a system. Unfortunately, such ...
4
votes
5answers
257 views
Can decoherence work when the environment itself is in a superposition without invoking collapse or splitting?
Decoherence is often presented as a program to solve the measurement problem using only the bare bones quantum mechanics framework of a Hilbert space and unitary Schrödinger time evolution. As ...
4
votes
1answer
48 views
Spekkens Toy Model, Internal Comonoids
I have been thinking about Spekkens Toy model in terms of interfaces. The Spekkens paper concerns a physics based on only being able to receive answers to half the number of questions necessary to ...
9
votes
1answer
61 views
Quasiparticles in Bohmian mechanics
My questions are about de Broglie-Bohm "pilot wave" interpretation of quantum mechanics (a.k.a. Bohmian mechanics).
Do quasiparticles have any meaning in Bohmian mechanics, or not? Specifically, is ...
2
votes
3answers
441 views
Defining Measurement in Quantum Mechanics
I should begin by saying that I am a total newbie when it comes to Quantum Mechanics. Therefore my question might sound metaphysical to people who know their stuff. So please forgive.
What I am ...
8
votes
1answer
442 views
The measure problem in the anthropic principle
The anthropic principle is based upon Bayesian reasoning applied to the ensemble of universes, or parts thereof, conditioned upon the existence of conscious observers. That still leaves us with the ...
