The double-slit experiment is a famous physics experiment that demonstrates the wave-particle duality of matter, which suggests that particles like electrons can exhibit both wave-like and particle-like behavior depending on how they are observed.
The double-slit experiment shows that the behavior of particles like electrons are dependent on the way they are being observed, and that they can exhibit properties of both waves and particles.
The delayed-choice quantum eraser experiment is a variation of the double-slit experiment that demonstrates the idea that a particle’s past can be affected by a measurement made in the present.
In this experiment, a beam of particles is split into two paths using a beam splitter. One path is directed towards a detector and the other path towards a second beam splitter that can be adjusted to direct the particles towards a second detector or a device that erases which path the particle took. The experimenter can choose to measure which path the particle took or to erase that information after the particle has already passed through the beam splitter.
The results of the experiment show that when the information about which path the particle took is erased, the particles exhibit wave-like behavior and produce an interference pattern on the detector, while when the information is retained, the particles act as particles and produce no interference pattern.
This experiment demonstrates that the act of measurement can affect the past behavior of a particle, and it has been interpreted as showing that the past is not fixed and that the present can influence the past. The delayed-choice quantum eraser experiment is considered as a further demonstration of the quantum weirdness and the idea that the classical reality is not the only one.