A quantum bus is a device that sends particles of energy (called "quanta") from one place to another. It works like a regular bus, in that it picks up passengers from different stops and then drops them off somewhere else. The difference is that the passengers on a quantum bus are actually quanta - tiny particles of energy, like light or electricity. Quanta can be moved around much faster than regular particles, so the quantum bus is a faster way to travel between two places.