How can particles appear from nothing?

This is known as the vacuum state. But as we will see, we cannot actually have zero-energy. Instead, the quantum field gently vibrates randomly. Sometimes this produces enough energy to form particles out of seemingly nothing!

Where do quantum particles disappear?

When they are reabsorbed, nothing of them remains except whatever momentum and kinetic energy (and sometimes other quantum numbers) they withdrew from the first particle and deposited with the second.

Do quantum particles change their behaviour when they are observed?

According to various studies conducted by physicists, quantum particle changes its behaviour in a double-slit experiment when it is being observed. Although, we can’t say for sure that whether the particles can be described by its particle behaviour or wave behaviour. That is why measurements are important.

Are there any experiments that demonstrate quantum phenomena?

Happily, a large number of experiments demonstrating weird quantum phenomena exist, covering a wide range of different types of systems. These use a bunch of different approaches to make the “quantum-ness” of the system manifest, but there are a couple of very general patterns in there.

How do we know that there is only one particle around?

With these, when you detect a single photon of a particular frequency at a particular spot, you know that there’s exactly one photon correlated with it arriving at a particular spot some distance away. So you can set up an experiment to manipulate and then detect that photon, and have confidence that it’s the only particle around.

Why is it called wave-particle duality of quantum mechanics?

This is why is it called the wave-particle duality of quantum mechanics. The experiments also suggest that when you observe the movements of the particles, it has an effect on the system. Physics is complicated, yet an interesting subject to major in.