Scientists at the University of California, Santa Barbara, and at Google reported on Wednesday in the journal Nature that they had made a significant advance that brings them a step closer to developing a quantum computer.

Researchers have been pursuing the development of computers that exploit quantum mechanical effects since the 1990s, because of their potential to vastly expand the performance of conventional computers. The goal has long remained out of reach, however, because the computers are composed of basic elements known as qubits that have remained, despite decades of engineering research, highly unstable.

In contrast to a bit, which is the basic element of a conventional computer and can represent either a zero or a one, a qubit can exist in a state known as superposition, in which it can represent both a zero and a one simultaneously.

If the qubits are then placed in an entangled state — physically separate but acting with many other qubits as if connected — they can represent a vast number of values simultaneously.