New experiments to help drive student interest in quantum technology

A team at the University of Barcelona in Spain has designed experimental equipment to help undergraduate students familiarise themselves with complex quantum physics.

The researchers say the project, described in a paper published in the journal EPJ Quantum Technology, will help students who want to pursue research into quantum technologies as the field enters a period of rapid boom.

UNESCO has declared 2025 the International Year of Quantum Science and Technology.

Entanglement is one feature of quantum mechanics which defies everyday experience. Entangled particles, such as 2 photons, can affect each other across space instantaneously.

This phenomenon troubled Einstein and other physicists who suggested in 1935 that there must be hidden variables to explain it.

In 1964, physicist John Bell responded to this question. He wondered what would happen if measurements were taken on each entangled particle separately. If there are hidden variables, as Einstein and co suggested, then this correlation between the measurements would be constrained – a constraint later called the “Bell inequality.”

Experiments in the 1970s and ‘80s showed that, as Bell predicted, the hidden variable theorem of Einstein wasn’t correct. Quantum mechanics just is that weird.

You can find out more about Bell inequalities in this article Cosmos produced on the 2022 Nobel Prize in Physics.

Quantum entanglement research is critical in upcoming quantum technology such as quantum computers and data encryption.

“The study of Bell inequalities – in particular, observing violations of the inequalities – is fundamental to characterising quantum entangled systems,” says co-senior author Bruno Juliá-Díaz. “It is important to be able to perform these experiments in a teaching laboratory to understand Bell’s inequalities, quantum entanglement and the probabilistic nature of quantum mechanics.”

Co-lead of the project, Martí Duocastella, says the team has created “new experimental equipment capable of providing students with direct measurements of quantum entanglement. From our perspective, we believe that allowing students to make these measurements will greatly facilitate their understanding of this unintuitive phenomenon”.

The system allows students to prepare different entangled states of photons.

“The new equipment has improved the photon-capture process: it uses detectors assembled to optical fibres, one of the key innovations to simplify the experiment, which facilitates the alignment of the system and increases the efficiency of the detection,” Duocastella and Juliá-Díaz say. “Thus, a complete measurement of the Bell inequalities can be performed during a practical laboratory session (between 1 and 2 hours).”

The relatively cheap and versatile equipment is already operational at University of Barcelona classrooms. They say it is also accessible in less specialised teaching scenarios.