Can the quantum eraser work without coincidence?

In summary: However, this filtering may affect momentum entanglement, but not polarization entanglement which is used in quantum eraser experiments. While this idea has been considered before, there is no known way to achieve interference detection without coincidence.
  • #1
Erik Ayer
75
4
I understand that downconverted light is not coherent, so that there are essentially many overlapping interference patterns and that coincidence detection filters out one of those patterns. However, could the downconverted light be filtered such that interference can be detected without coincidence? I imaging this being done with something like a long tube that absorbs light going off at angles rather than straight through the tube - it would only allow light in the polarization-entangled parts of the intersecting degenerate cones through.

This would, of course, screw up the momentum entanglement. However, the entanglement used in the quantum eraser is polarization, which should not be affected by the spatial filtering. I'm sure gobs of people have thought of this before me but I haven't run across any sort of discussion on it.
 
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  • #2
Does anyone have any insight?The short answer is that it is not possible to filter downconverted light in such a way that interference can be detected without coincidence. The reason for this is that downconverted light does not exist in an interference state until it is interfered with another light beam. In other words, the interference pattern in downconverted light is generated by the overlap of two beams. This means that in order to detect interference from downconverted light, you need to interfere it with another light beam and then use coincidence detection to filter out the desired pattern. Filtering out the light going off at angles will not help in this regard, as it will not generate an interference pattern.
 

1. What is the quantum eraser experiment?

The quantum eraser experiment is a thought experiment in quantum mechanics that demonstrates the wave-particle duality of light. It involves using a double-slit apparatus to observe the interference pattern of a single photon, and then using a "quantum eraser" to determine which slit the photon passed through.

2. How does the quantum eraser work?

The quantum eraser works by using a delayed choice setup, where the decision to observe the interference pattern or determine the path of the photon is made after the photon has already passed through the double-slit. This allows for the interference pattern to be observed even when information about the path of the photon is obtained.

3. Can the quantum eraser work without coincidence?

No, the quantum eraser experiment relies on the concept of coincidence, where two particles are correlated in a way that their properties cannot be determined individually. Without this correlation, the interference pattern cannot be observed and the quantum eraser cannot work.

4. What is the significance of the quantum eraser experiment?

The quantum eraser experiment is significant because it demonstrates the strange and counterintuitive nature of quantum mechanics, where particles can exist in multiple states at once and their behavior is influenced by the act of observation. It also has practical applications in quantum cryptography and quantum computing.

5. Are there any limitations to the quantum eraser experiment?

Yes, the quantum eraser experiment is limited by the uncertainty principle, which states that it is impossible to simultaneously know the exact position and momentum of a particle. This means that the interference pattern can only be observed for particles with certain energy levels and not for all particles.

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