Ride the Lightning - the British Interplanetary Society has published a new starship concept by the name of VARIES, which stands for “Vacuum to Antimatter-Rocket Interstellar Explorer System”. The exotic spaceship is designed to extract propulsive energy from the quantum fluctuations of space itself.
The principle behind VARIES is as simple as it is theoretically cutting edge. It’s based on something from quantum mechanics called a “Schwinger pair production.” According to quantum theory, particles in a vacuum don’t exactly exist. They’re only “sort of” there as an expression of probability […] if you tip the scales of probability by subjecting a vacuum to a powerful electric field, it will cause particles of matter (or antimatter) to spontaneously appear.
If this phenomenon pans out, VARIES would exploit it by way of an unmanned starship with huge solar panels that would collect the sun’s rays. These would, in turn, power banks of x-ray free electron lasers to charge the vacuum and create antimatter, which would then be collected and stored aboard as fuel for the journey.
There are some neat videos explaining the physics in more detail.