Measuring atoms in time could give physicists a better understanding of the world at the quantum scale, and lead to new possibilities in the fields of quantum computing and cryptography.

Fundamental Research

Quantum mechanics – the theory that describes the physical properties of nature at the scale of atoms and subatomic particles – is mysterious, fascinating and at times bewildering. This is in part because the laws that govern classical physics are simply insufficient to fully explain what happens at this scale. “The theory of quantum mechanics began to be developed around 100 years ago, as a means of explaining the properties of atoms,” explains TempoQ project coordinator Otfried Gühne from the University of Siegen in Germany. “This was very much a fundamental theory. Then, in the 1980s and 1990s, researchers began to realise that quantum mechanics could have implications for information processing.” In particular, physicists discovered that algorithms run on a quantum computer (a device that harnesses the collective properties of quantum states) could solve certain problems faster than a classical computer. Scientists also showed that quantum phenomena could be used in cryptography, to make information communication even more secure. “Important developments have also been made on the experimental side,” adds Gühne. “In the past few decades, researchers have been able to trap and manipulate single atoms.”

Temporal correlations

The TempoQ project, funded by the European Research Council, sought to build on these developments, in both theory and experimentation, to examine specific phenomena at the quantum scale. While many researchers have looked at the spatial correlations between atoms to better understand quantum mechanics, Gühne and his team decided to look at temporal correlations. In other words, measurements were taken of the same atom but at different time periods. Gühne and his team then examined what these measurements might tell us about the quantum world. “This project was very fundamental, and closer to mathematics than any practical application as such,” notes Gühne. “In particular, we were interested in identifying certain measurements that could only be explained using quantum theory.”

Quantum discoveries

The experiments conducted by Gühne and his team have advanced a general theory of temporal correlations at the quantum level, and helped to prove some quantum properties that would not have been possible through the application of classical physics theory. “The fundamental nature of TempoQ also enabled us to address some open questions about the nature of quantum mechanics,” says Gühne. “This wasn’t planned at the beginning of the project, but we actually managed to resolve a conjecture about quantum temporal correlations that has been around for 25 years! The postdoc researcher who worked on this even won a prize for this discovery.” The success of the project has also raised the profile of Gühne’s research group, and helped to attract researchers and teachers to the lab. And while the research has not led to any immediately identifiable innovations or products, Gühne explains why fundamental science is so critical. “First, basic research is interesting in itself,” he remarks. “If you think about the initial research into things like quantum cryptography and computing in the 1980s – this was all completely speculative and theoretical. Lasers for example, which are used across numerous sectors, was an area of fundamental research up until the 1960s. Only then did people start to look at possible applications.” To this end, Gühne believes that the TempoQ project has made an important contribution to the field of quantum theory, where future applications in computing, cryptography and other sectors could one day transform our lives.

Keywords

TempoQ, quantum, physics, computing, cryptography, mechanics, atoms, lasers