Google started working on a form of quantum computing that harnesses superconductivity in 2014. In 2017 or 2018 Google hopes to perform a computation that is beyond even the most powerful 'classical' supercomputers — an elusive milestone known as quantum supremacy. Its rival, Microsoft, is betting on an intriguing but unproven concept, topological quantum computing, and hopes to perform a first demonstration of the technology.

The quantum-computing start-up scene is also heating up. Christopher Monroe, co-founded the start-up IonQ in 2015, plans to begin hiring in earnest this year. 

Physicist Robert Schoelkopf at Yale University in New Haven, Connecticut, who co-founded the start-up Quantum Circuits, and former IBM applied physicist Chad Rigetti, who set up Rigetti in Berkeley, California, say they expect to reach crucial technical milestones soon.

The largest trapped ion quantum computer with 20 qubits is being tested in an academic lab led by Rainer Blatt at the University of Innsbruck in Austria.