How do we know that subatomic particles exist in superposition?
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It’s not so much that we *know* particles exist in superposition, but it’s the least complicated explanation for what we observe experimentally.
The classic example is the “double-slit” experiment in which light is sent towards a screen through a partition with two narrow openings to make a distinctive pattern of bright and dark lines. This interference pattern is the result of waves adding together in some places and canceling each other out in others. The curious thing is that the same pattern appears on the screen even when you send one photon (or one electron or even one atom) through the partition at a time. On the everyday familiar scales of classical physics, this shouldn’t happen because there wouldn’t be anything to add or cancel out the effect of each individual particle moving through one or the other slit.
The fact that we still see interference patterns built up from particles this way suggests that there’s something causing each individual particle to act as if it was interfering with a particle that went through the other slit at the same time, even though we can observe only one hitting the screen at a time. The prevailing interpretation of this experimental result is that, at least until the particle hits the screen, the particle’s location isn’t entirely on either path alone through the partition, but exists in a real sense on both paths. We see the same results when we measure other phenomena on quantum scales like energy levels.
The most straightforward answer would refer to a landmark experiment performed in 1801 by Thomas Young referred to as the double slit experiment.
This experiment used subatomic particles of light, or “photons”. In the experiment, individual photons were aimed single file at a partition which had only two openings. Each opening was so small that only one photon could fit through it at a time.
However, the results showed that each single photon passed through BOTH openings simultaneously.
There is more nuance to it but that’s the ELI5 version.
It’s not so much that we *know* particles exist in superposition, but it’s the least complicated explanation for what we observe experimentally.
The classic example is the “double-slit” experiment in which light is sent towards a screen through a partition with two narrow openings to make a distinctive pattern of bright and dark lines. This interference pattern is the result of waves adding together in some places and canceling each other out in others. The curious thing is that the same pattern appears on the screen even when you send one photon (or one electron or even one atom) through the partition at a time. On the everyday familiar scales of classical physics, this shouldn’t happen because there wouldn’t be anything to add or cancel out the effect of each individual particle moving through one or the other slit.
The fact that we still see interference patterns built up from particles this way suggests that there’s something causing each individual particle to act as if it was interfering with a particle that went through the other slit at the same time, even though we can observe only one hitting the screen at a time. The prevailing interpretation of this experimental result is that, at least until the particle hits the screen, the particle’s location isn’t entirely on either path alone through the partition, but exists in a real sense on both paths. We see the same results when we measure other phenomena on quantum scales like energy levels.
The most straightforward answer would refer to a landmark experiment performed in 1801 by Thomas Young referred to as the double slit experiment.
This experiment used subatomic particles of light, or “photons”. In the experiment, individual photons were aimed single file at a partition which had only two openings. Each opening was so small that only one photon could fit through it at a time.
However, the results showed that each single photon passed through BOTH openings simultaneously.
There is more nuance to it but that’s the ELI5 version.
It’s not so much that we *know* particles exist in superposition, but it’s the least complicated explanation for what we observe experimentally.
The classic example is the “double-slit” experiment in which light is sent towards a screen through a partition with two narrow openings to make a distinctive pattern of bright and dark lines. This interference pattern is the result of waves adding together in some places and canceling each other out in others. The curious thing is that the same pattern appears on the screen even when you send one photon (or one electron or even one atom) through the partition at a time. On the everyday familiar scales of classical physics, this shouldn’t happen because there wouldn’t be anything to add or cancel out the effect of each individual particle moving through one or the other slit.
The fact that we still see interference patterns built up from particles this way suggests that there’s something causing each individual particle to act as if it was interfering with a particle that went through the other slit at the same time, even though we can observe only one hitting the screen at a time. The prevailing interpretation of this experimental result is that, at least until the particle hits the screen, the particle’s location isn’t entirely on either path alone through the partition, but exists in a real sense on both paths. We see the same results when we measure other phenomena on quantum scales like energy levels.
The most straightforward answer would refer to a landmark experiment performed in 1801 by Thomas Young referred to as the double slit experiment.
This experiment used subatomic particles of light, or “photons”. In the experiment, individual photons were aimed single file at a partition which had only two openings. Each opening was so small that only one photon could fit through it at a time.
However, the results showed that each single photon passed through BOTH openings simultaneously.
There is more nuance to it but that’s the ELI5 version.
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