Researchers believe these devices could one day speed the creation of new medicines, power advances in artificial intelligence and summarily crack the encryption that protects computers vital to national security. In 2019, Google announced that its machine had reached what scientists call "quantum supremacy," which meant it could perform an experimental task that was impossible with traditional computers. Part of the challenge is that a qubit breaks, or "decoheres," if you read information from it -- it becomes an ordinary bit capable of holding only a 0 or a 1 but not both. But by stringing many qubits together and developing ways of guarding against decoherence, scientists hope to build machines that are both powerful and practical. Ultimately, ideally, these would be joined into networks that can send information between nodes, allowing them to be used from anywhere, much as cloud computing services from the likes of Google and Amazon make processing power widely accessible today.

From Santa Barbara, California, to Hefei, China, scientists are developing a new kind of computer that will make today's machines look like toys. Harnessing the mysterious powers of quantum mechanics, the technology will perform tasks in minutes that even supercomputers could not complete in thousands of years. In the fall of 2019, Google unveiled an experimental quantum computer showing this was possible. Two years later, a lab in China did much the same. But quantum computing will not reach its potential without help from another technological breakthrough.