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Results tagged with faster-than-light
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user 28512
"Faster-than-light", also known as superluminal velocities, refers to any sort of travel at a speed greater than the speed of light. Prohibited in mainstream physics due to the Special theory of relativity.
5
votes
"FTL" Communication with Quantum Entanglement?
Quantum entanglement can't be used to send any information faster than light. Suppose you have two electrons with entangled spins, and that you can measure the spin along the x,y or z directions. Rega …
- 10.2k
4
votes
About the nonlocality of QM and faster-than-light/backward-in-time machines
Quantum mechanics has not been shown to be non-local. Rather, hidden variable theories that make the same predictions as quantum mechanics are non-local. Quantum systems can be described in terms of o …
- 10.2k
1
vote
Can entanglement witnesses on GHZ states with $n > 2$ violate the non-communication theorem?
For each individual photon in the GHZ state, the expectation values of each measurement are unaffected by measurements on any of the others. The only way to tell if the remaining two photons in the GH …
- 10.2k
0
votes
Communication via teleportation/entanglement (FTL communication)
Teleportation and entanglement do not involve FTL communication of any kind. There is a local description of the evolution of any given quantum system in terms of its Heisenberg picture observables. T …
- 10.2k
1
vote
Why can't we break the speed of light in vacuum?
There is no faster than light communication or motion in quantum mechanics. This is a misunderstanding that is common even among physicists.
In classical physics, a system can be described by a set o …
- 10.2k
0
votes
Accepted
A quantum entanglement experiment
Suppose we have an entangled electron-positron pair, such that total spin is zero. Separate them, and let Alice measure the spin (along zz) of the electron, obtaining, say, +1/2,+1/2. All the subse …
- 10.2k
4
votes
Is quantum entanglement functionally equivalent to a measurement?
A measurement is an interaction that allows some information about a quantum system to be copied. (The information that can be copied is something like the value of one particular observable or POVM, …
- 10.2k
1
vote
What are the implications of the EPR bridge information metric being invariant under all con...
Invariance of the laws of physics under displacements doesn't imply entanglement, since classical theories that don't have entanglement are also invariant under displacement:
https://arxiv.org/abs/hep …
- 10.2k
0
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Could reducing entanglement by unitary operations allow for FTL-communication? (and why not?)
You write:
So even though we shift the polarization for the upper EPR particle to have the same polarization in both paths of the upper apparatus, the state of the entangled other EPR particle will s …
- 10.2k
0
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Quantum entanglement: does it necessarily imply superluminal information transfer?
Entanglement does not imply any faster than light information transfer. Rather, each system exists in multiple versions and those versions are matched up in the appropriate way when the measurement re …
- 10.2k
1
vote
Thought experiment using quantum entanglement in position and its effects
Your thought experiment does have a major flaw. According to quantum mechanics in any measurement of two spatially separated atoms a and b what happens to b has absolutely no effect at all on the prob …
- 10.2k
1
vote
Can a non-local theory be consistent with special relativity?
Bell's theorem states that a theory that is local and describes observable quantities in terms of stochastic variables that have a single value at the time of measurement picked with the relevant prob …
- 10.2k
1
vote
Faster-Than-Light Communication using Entangled Photons
The diagram of the experiment has a large box bearing the legend "coincidence counter". The experiment is measuring fringes in the probability of a match in the photons' location. The probability for …
- 10.2k
1
vote
Accepted
Potential FTL Implications of quantum "weak measurement"?
In quantum mechanics, systems can only affect one another through local interactions. In an entangled pair of systems $S_1,S_2$, $S_1$ contains information about $S_2$ but that information can't be re …
- 10.2k
0
votes
Quantum entanglement, how do we know there was no spin?
Suppose you have two electrons in a state of entangled spin. Suppose also that you can measure the spin for each electron along one of two axes the x axis or the z axis. Regardless of what axis you ch …
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