Welcome Physics World  May 2021

Big milestones, big dreams

What is the best way to talk about a field that brims with promise but hasn’t (yet) delivered on its world-changing ambitions? Judging from the scientists whose work appears in this Physics World Quantum Science & Technologies Briefing, the answers are as varied as the scientists themselves. Some at the more industrial end of the field focus on areas where the goals are less grandiose, but progress is very much in evidence. Take Bruno Desruelle. As the chief executive of Muquans, a quantum gravimetry start-up, Desruelle can point with pride to the gravity-sensing units his company built and tested on the slopes of Italy’s Mount Etna (“Converting quantum promises into commercial realities”). “I sometimes hear the question about what will be the first real-life application of quantum technologies,” he told an audience at the 2021 Quantum West conference. “Well, there are already some quantum instruments that are in service now.”

Others keep their eyes firmly on the horizon. Ilyas Khan, the founder and chief executive of Cambridge Quantum Computing, no doubt speaks for many when he says that he and his colleagues “believe very strongly that quantum computing will end up being one of the largest segments of the global economy” (“From infancy to adolescence”). Though Khan does hedge his bets on the timing of this happy event (“whether it’s in five years, or 10 years or 20 years”), big dreams are a major part of quantum’s appeal – for physicists as well as for government agencies and private investors funding quantum research and development.

Perhaps the most common way of talking about quantum, though, is with a mixture of optimism and caution. A good example of this approach comes from Anders Sørensen, a physicist at Denmark’s Niels Bohr Institute who praised researchers at the Delft University of Technology in the Netherlands for developing the first three-node quantum network, while also advising of “formidable challenges” involved in scaling it up (‘Three-node quantum network makes its debut’). Raymond Laflamme, the founding director of the Institute for Quantum Computing at the University of Waterloo, Canada, likewise produced a classic of cautious optimism when he described another team’s work on quantum error correction as “the first milestone in a family of experiments that will end up producing a reliable quantum computer” (‘“Lattice surgery” entangles fault-tolerant topological qubits’).

In selecting articles for this briefing, I’ve tried to balance dreams with milestones. The section on quantum computing includes articles on most major qubit types, some of which are currently much further along the developmental road than others. Articles on quantum materials and quantum simulation explore devices and techniques that could have important near-term implications for scientific research, if not yet for commercial products. Finally, a section on quantum fundamentals reminds us that the future of quantum science may lie in areas we’ve barely even dreamed about.