Petta said his team's finding could eventually allow engineers to build quantum computers consisting of millions of quantum bits, or qubits. So far, quantum researchers have only been able to manipulate small numbers of qubits, not enough for a practical machine.
"The whole game at this point in quantum computing is trying to build a larger system," said Andrew Houck, an assistant professor of electrical engineering who is part of the research team.
For years, teams of scientists have pursued the idea of using quantum mechanics to build a new machine that would revolutionize computing. The goal is not build a faster or more powerful computer, but to build one that approaches problems in a completely different fashion.
"The point of a quantum computer is not that they can do what a normal computer can do but faster; that's not what they are," said Houck. "The quantum computer would allow us to approach problems differently. It would allow us to solve problems that cannot be solved with a normal computer."
One challenge facing scientists is that the spins of electrons, or any other quantum particles, are incredibly delicate. Any outside influences, whether a wisp of magnetism or glimpse of light, destabilizes the electrons' spins and introduces errors.
Over the years,
scientists have developed techniques to observe spin states without
disturbing them. But analyzing small numbers of spins is not enough;
millions will be required to make a real quantum processor.
To approach the problem, Petta's team combined techniques from two branches of science. From materials science, they used a structure called a quantum dot to hold and analyze electrons' spins. From optics, they adopted a microwave channel to transfer the spin information from the dot.
"The methods we are using here are scalable, and we would like to use them in a larger system," Petta said. "But to make use of the scaling, it needs to work a little better. The first step is to make better mirrors for the microwave cavity."