Open quantum system

Okay kiddo, imagine you have a toy train that's running on its own. You can see it moving around the track, but you can't control it or interact with it directly. Maybe it's going through a tunnel or over a bridge that you can't see inside of. This train is like something called an open quantum system, which is something scientists study to understand how it behaves even though they can't observe or control every little detail.

In real life, open quantum systems are things like atoms, molecules, and other tiny particles that interact with their environment in ways that we can't always predict or measure. They might be affected by things like temperature, pressure, or electromagnetic fields that we can't directly observe or control. But scientists can still study how these systems behave by making measurements and using mathematical models to make predictions about how they might change over time.

One way scientists study open quantum systems is by looking at their "density matrix," which is like a sort of map that shows all the different ways the system can be in different states at the same time. This might sound a little weird, but it's actually really helpful for understanding how these systems behave and how they might interact with other particles or objects in their environment.

So basically, an open quantum system is something that we can't control or observe directly, but we can still learn a lot about how it behaves by studying its density matrix and making predictions about how it might change over time. It's like watching a toy train from a distance and trying to figure out where it might go next based on what we know about how it moves and interacts with its surroundings.