q**i
发帖数: 174 | 1 one can design a quantum computer where a change in one partical's quantum
status can impact quantum status of another partical. a signal (a
change in a partical's quantum status) can be transmitted to a remote party
through such a quantum device.
Question: is the transmission instantaneous? or at a speed less than that
of light (or if the process is superluminal?) | l**********n
发帖数: 72 | 2 Some of my understandings to the problem.
First, consider the EPR experiments and many similar experiments, the
macroscopically separated particles are in a coherent state, and when you
measure the state of one particle at A locally, the state of another particle
far apart at B is determined by the measurement at A. This is the basic
assumption of Quantum Mechanics at the present stage. And the collapse of the
quantum state is NOT transmitted via electromagnetic interaction.
Second, when the mac | l**********n
发帖数: 72 | 3 Not so. You can first encode the information in the quantum state and then
control the measurement to get the information at another point. Such as the
EPR experiment, you could set the spin up state is that "The enemy is coming!"
and the spin down state to be "The rabbit is coming!" OK? :) When the
particles departed, they carries the entangled information. Then when the
particle reached the soldiers at point A and they saw the rabbit, they set
their communication tool to make the particle poin | l**********n
发帖数: 72 | 4 That's easy. That means particle is in an entangled state a|up>+b|down>, where
a, b are complex variables to include the phase. Then the particle impinges on
a highly polarized thin film with atoms all pointing to spin up, so |up>. The
interaction between the particle and thin film of atoms are v(r), therefore,
the possibility of flipping up is
/(+), so, I could make the
interaction perferable to |up> state.
Don't confuse too much with the quantum state | m******o
发帖数: 33 | 5 long time no QM, but your setup is not convincing. put spacial states in
and calculate again, no way it's gonna work. if information can be transmitted
faster than light, in last 2 years, I should know:)
(I can raise one question: if you put strong external force, the total spin
of two particles no longer conserve)
【在 l**********n 的大作中提到】
: That's easy. That means particle is in an entangled state a|up>+b|down>, where
: a, b are complex variables to include the phase. Then the particle impinges on
: a highly polarized thin film with atoms all pointing to spin up, so |up>. The
: interaction between the particle and thin film of atoms are v(r), therefore,
: the possibility of flipping up is
: /(+), so, I could make the
: interaction perferable to |up> state.
: Don't confuse too much with the quantum state
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