Quantum Simulators Leap Ahead
In the daunting quest to build full-blown, universal #quantumcomputers, capable of tackling problems beyond the reach of today’s classical machines, the creation of so-called quantum simulators has offered a tempting interim target. These simulators are designed not to be arbitrarily programmable, but instead to model specific quantum systems that conventional computing algorithms can’t easily replicate. A sufficiently large simulation would demonstrate quantum computing’s potential power—and, perhaps, offer a platform for moving toward general-purpose quantum machines. At the end of November 2017, two U.S. research groups announced a big step forward in such quantum simulation. Leveraging different systems of trapped atoms or ions, the two groups were able to confine and manipulate more than 50 individual interacting quantum bits, or qubits, and to use them to simulate physics all but intractable with a classical computer (Nature, doi: 10.1038/nature24622, 10.1038/nature24654). A third research team based in the United States, Singapore and Greece performed a separate quantum simulation, using nine qubits, on a very different, superconducting-circuit platform involving a quantum chip from Google (Science, doi: 10.1126/science.aao1401). None of the systems is a fully formed quantum computer—yet. But some of them could be configured to solve a specific class of difficult optimization problems that crop up in a variety of areas, as well as other problems in quantum physics. And, with additional engineering to scale up the number of qubits and the lasers, control systems and circuits that manage them, the simulators could evolve closer and closer to full-scale quantum computers.