Shrodinger's Cat Paradox: A Possible Solution

[Careful]

I'm not sure what you mean exactly here. The only thing that the junction (if that is what you meant by "bridge") affects on the josephson current is the current amplitide, not the phase, via the Ambegaokar-Baratoff relationship.

In any case, there has to be something that correlate the two currents. What would this be?

Zz.

I quickly glanced upon the Leggett paper, in particular formulae 5.22, 5.23 which give the eigenstates for an effective Hamiltonian in which cooper pairs can tunnel through the (bridge) junction (a so called classically forbidden phenomenon). The latter states, expressed in the eigenstates of the Hamiltonian in which tunneling is forbidden depend upon a tunneling amplitude and the energy of the latter. Personally, I do not know what is ``strange'' about this (there is nothing weird about tunneling).

Careful

 

[ZapperZ]

I quickly glanced upon the Leggett paper, in particular formulae 5.22, 5.23 which give the eigenstates for an effective Hamiltonian in which cooper pairs can tunnel through the (bridge) junction (a so called classically forbidden phenomenon). The latter states, expressed in the eigenstates of the Hamiltonian in which tunneling is forbidden depend upon a tunneling amplitude and the energy of the latter. Personally, I do not know what is ``strange'' about this (there is nothing weird about tunneling).

Careful

My reference to tunneling was for the generic field. In tunneling spectroscopy in particular, for a superconductor-insulator-superconductor junction, you get what is known as the Josephson current whereby at zero bias, a spontaneous current flows in BOTH directions. We (I) see this in the I-V curve of the tunnel junction. If you look at the state describing this, it is really a superposition of currents in both directions, not separate currents in both directions. A clear effect of this is on how the probability of each direction can shift depending on from which direction you approach zero bias.

So the very same principle is also at work in a totally different experiment than the SQUID experiment.

Zz.

 

[vanesch]

My point, on the other hand, is that if you perform a position measurement on |N,0> + |0,N> then you will see no difference between this and the mixture: |N,0> with prob. 1/2 and |0,N> with prob. 1/2, provided N is large enough.

Of course, for a given measurement basis, you cannot distinguish between a pure state and the corresponding mixture.
So, it is necessary to change measurement basis in order to even hope to find a difference between the pure state and the mixture.

 

[Careful]

My reference to tunneling was for the generic field. In tunneling spectroscopy in particular, for a superconductor-insulator-superconductor junction, you get what is known as the Josephson current whereby at zero bias, a spontaneous current flows in BOTH directions. We (I) see this in the I-V curve of the tunnel junction. If you look at the state describing this, it is really a superposition of currents in both directions, not separate currents in both directions. A clear effect of this is on how the probability of each direction can shift depending on from which direction you approach zero bias.

So the very same principle is also at work in a totally different experiment than the SQUID experiment.

Zz.

I do not follow now : I acknowledged there is a superposition of currents in both directions, we simply do not agree whether this is a mysterious superposition of two states of one current or two separate (correlated) interfering currents, that's all.

 

[demo001]

This experiment is fataly floored.
you will never find an alive cat this is why.
quantum superposition
In the experiment Shrodinger explains that the qubit is in quantum superposition however it then goes on to ignore the simple fact that in superposition the qubit is in all states at once.
He goes on to explain correctly we will not know what state it will come to rest in until we open the box.
Nothing radical there is there?
However the simple fact ignored is in the superposition state of the qubit and the fact that the switch is looking for just one state a state that the superpositioned qubit will always exibit when inside the box before opened. Therefore the gas is always released long before the box is ever opened the cat can never be alive.
The only way a cat could ever be alive would be if the qubit was never in superposition in the first place in which case the experiment failed before it starts.
At best this experiment can only prove superposition eg the case of the cat being dead but the qubit when observed not being in the correct state to have triggerd the switch.

 

[Demystifier]

I am reading "Beyond Einstein" by Kaku and one quote in the book specially caught my attention.

"... the superstring theory provides ... comprehensive way of looking at Schrodinder's cat. Usually, in quantum mechanics, physicists write the Schrödinger wave function of a certain particle. However, the complete quantum mechanical description of the superstring theory requires that we write the Schrödinger wave function of the entire universe... This does not resolve all the philosophical problems associated with Schrödinger's cat; it merely means that the original formulation of the problem ... may be incomplete."

I have published several papers in peer-reviewed journals on the relation between string theory and the measurement problem in QM, so I guess someone could call me an expert for such stuff. Still, the quote above does not make any sense to me.