We all send sensitive data such as credit card information over the internet daily. Internet security currently relies on several computational assumptions. For example, the security of a well-known public-key encryption scheme—the so-called RSA cryptosystem—hinges on the belief that no efficient algorithm for performing prime factorization of large integers will appear in the next decade on conventional computers. But a quantum computer could efficiently factor large integers and thus break the most widely used public-key encryption schemes, including the RSA and elliptic curve cryptosystems.1 Put simply, when a fully functioning quantum computer is built, much of conventional cryptography will fall apart.
Motivated by that eventuality—and by the many potential future applications of quantum computers in biomedicine, chemistry, artificial intelligence, and other fields—researchers have recently made tremendous progress toward constructing a large-scale, universal quantum computer. (To learn about how quantum hardware is becoming increasingly accessible, see the article by Harrison...
