The word "quantum" is proliferating into nearly every facet of modern technology. There's quantum computers, of course, but also quantum hard drives, quantum internet, and yes, even quantum engines. However—as is true with all of these other "quantum" technologies—this isn't your typical piston/combustion situation. Instead, these engines leverage the wonky properties of quantum mechanics to induce mechanical motion.

Although an incredibly nascent technology, quantum engines come in a couple different flavors. Last year, scientists at the Okinawa Institute of Science and Technology developed a quantum engine that leveraged the complicated interplay between fermions and Bose-Einstein condensates. This created energy by replacing heat (the typical energy source of an ICE engine) with the "quantum nature of the particles in the gas," a press statement read at the time. This engine had an efficiency of 25 percent—not bad for a first go at it, but nowhere close to becoming a practical engine.