But what if we introduce quantum theory into the problem? The scientists imagine measuring a quantum atomic clock experiencing two different times while it is placed in superposition—a quirk of quantum mechanics in which something appears to exist in two places at once. “It’s kind of like ‘Schrödinger’s clock,’” Smith says. “You can actually combine the superposition principle in quantum mechanics with this notion of time dilation in relativity,” he says. “It’s exactly Einstein’s twins but now applied to the same system.