Quantum Field Theory in A Cavity

Free field theory
Left: fluctuations of a quantum field around a 51-particle state in a mirrored cavity. Right: what the state looks like without fluctuations.

So I’m still mired in final exams–this time a final project for my quantum field theory course.  The downside is that it will be yet another week before my next “real” post. The upside is that I still have a little something for you all this week. The above image shows part of what I’m working on for my project.

Imagine that you make a square box of mirrors, and with some magic quantum tweezers, you put exactly fifty-one photons into your box. Light is a special oscillation in an electromagnetic field, which we usually describe classically. But if we only have fifty-one photons…we need quantum mechanics. What do we do?

Quantum mechanics is a theory of probabilities, so we need to make the field behave probabilistically. What we do is enforce the Heisenberg uncertainty principle on our field and allow it–nay, force it to wobble randomly. That’s what my image shows; I modeled a massive scalar field, which is simpler than the electromagnetic field but an acceptable approximation for our purposes. The right plot shows the field before you throw in quantum mechanics.  The left plot shows one measurement of the field after you throw in quantum mechanics. Each time we measure the field, it will look like some random fluctuation around the plot on the right.

Cool, huh? I promise I’ll have a real post on quantum field theory at some point.