In two papers published today in the journal Nature, a team at MIT and Harvard in Cambridge, Massachusetts, and another from the University of Maryland and the National Institute of Standards in Washington D.C., reveal that they have built specialized types of quantum calculator, each of which uses more than 50 qubits—well beyond what had been demonstrated previously. In both cases, the researchers created quantum simulators, machines capable of using analog calculations to model how quantum particles interact.

The two systems both use atoms but work in different ways. The MIT-Harvard system handles 51 qubits by using lasers to trap neutral atoms in an excited state. The Maryland-NIST machine, which handles 53 qubits, traps ytterbium ions in place using gold-coated electrodes. Together, they suggest that an alternative approach to building quantum machines might yet have the potential to challenge the one being pursued by industry.

“While our system does not yet constitute a universal quantum computer, we can effectively program it by controlling the interactions between the qubits,” says Mikhail Lukin, a physicist at Harvard who developed on of the systems in collaboration with Vladan Vuletic at MIT.

Will Zeng, a researcher at Rigetti Computing, a company that has received tens of millions in venture funding to pursue quantum computing, says quantum simulation at this scale is a significant step. In fact, simulating quantum effects was the original purpose for a quantum computer proposed by physicist Richard Feynman more than 40 years ago. Now scientists “are able to show some of the potential inherent in quantum computers, so the results are exciting,” he says.

Quantum computers work in a fundamentally different way from conventional computers. While a normal computer takes binary bits of information, encoded as either 1 or 0, and performs calculations on them one after another, a quantum computer exploits two counterintuitive features of quantum mechanism—entanglement and superposition—to perform calculations in parallel. As a result, it can calculate with large amounts of information in far less time. Several dozen quantum bits can perform computations on billions of pieces of information in one step.

The technology remained a pipe dream among physicists for years, but it undoubtedly has enormous potential. Excitement is now growing about finally building machines capable of doing useful work.

The 50-qubit benchmark is significant because around that point, quantum machines become capable of performing calculations that would be difficult, if not impossible, to run on even the most enormous supercomputer available. Some scientists refer to this as “quantum supremacy” (see “Google Reveals a Blueprint for Quantum Supremacy” and “IBM Raises the Bar with a 50-Qubit Quantum Computer”). Both IBM and Google are developing general-purpose superconducting quantum computers capable of using around the same number of qubits.