Researchers led by PhD graduate Erik Lucero of the University of California-Santa Barbara built a quantum processor to map the number 15. The team built a quantum circuit made of four superconducting qubits, which are the logic gates of a quantum system, on top of a substrate made of sapphire. It also contained five microwave resonators. The fabrication itself was a breakthrough, because organizing nine separate quantum pieces required very precise, automated construction methods. The qubits were entangled and verified using quantum experiments. Then the team used this circuit to factor 15 using Peter Shor's factoring algorithm. That code says for any given integer N, the computer must find its prime factors. But it does this quantum-fast, finding the solution exponentially faster than the quickest known classical factoring algorithm.