system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Quantum Zeno Effect and how it relates to Zeno's paradoxes.
gpt
I'll try with a toy example and cover the important points in quantum mechanics. Take out pen and paper. :)
 Draw a coordinate system and a unit circle of radius one with center in (0,0). This is the *quantum system*. Now consider a vector pointing from (0,0) to some point on the unit circle. This is the *state* of the quantum system. Also known as the *state vector*. Such a vector is *always* of length one.

At any point you can tell the state vector to "collapse " to either the x axis or the y axis. You can't choose which one, it will do this randomly. The bigger the projection is on the corresponding axis, the more likely it is the state vector will collapse to that axis. This is called a *measurement*.

Sometimes the state of a system can be *time dependent*. It changes over time. In our case that means the vector will rotate around the unit circle according to some rule. 

Now, the Zeno effect! lets say you start out with a state vector in  (1,0), that is at one on the x axis and zero on the y. After a tiny fraction of a second you tell it to collapse to the x or y axis. But the vector is so close to the x axis it's almost certain to collapse to it. Then after another fraction of a second you ask it again. And again and again. The vector never gets a chance to get close enough to y axis to ever have any real chance of collapsing to it. That's the Zeno effect. *You keep measuring a quantum system over and over again and thereby forcing it to remain in the same state forever.*

Edit: Clarified a few things.