New possibilities for quantum breakthroughs at the Ångström Laboratory

The slim, oblong unit occupies about half of the lab space, including its adjacent measuring station. Nothing reveals that the equipment has a unique capability: to reveal quantum phenomena at a previously unattainable level. This instrument, called dilution refrigerator, has the ability to cool samples to temperatures colder than the coldest regions of the universe, close to absolute zero. These extreme conditions enable researchers to observe and track quantum phenomena with a precision that was previously impossible.

This, according to Venkata Kamalakar Mutta, Senior Lecturer in Quantum Technology and Director of the Quantum Materials Device (QMD) lab.

“The dilution refrigerator provides us with the conditions we need to make groundbreaking discoveries in quantum materials and quantum matter, individual quantum systems, and quantum components for future technologies. We’ve been waiting for this new ‘toy’ for a long time, which we’ve given the name ELSA,” says Venkata Kamalakar Mutta with a smile.

ELSA, or the Emergent Low-Temperature Spin Phenomena Lab, is a milestone in the expansion of the QMD lab because of its unique capabilities in Sweden. The work at QMD is also connected to Myfab Uppsala, which is part of a national research infrastructure for microtechnology, nanoscience and materials research.

“Together with ELSA and our existing experimental capabilities at QMD and the Ångström Laboratory, Uppsala University is now one of the finest experimental environments for quantum research in the Nordic countries,” he adds.

Uncertainty as a fundamental quantum principle

But when does something become ‘quantum’? According to Venkata Kamalakar Mutta, the behaviour of a particle enters the realm of quantum mechanics when its size becomes comparable to its wavelength. Everyday objects are far too large.

“In measuring the motion of the quantum particle, its location becomes uncertain. And conversely, in measuring where the quantum particle is, its motion becomes uncertain.”

The elusive nature of quantum particles has been illustrated with countless examples; the most famous of which is perhaps Schrödinger’s cat. In a box containing a hypothetical cat, there is also a radioactive source with a 50/50 chance of decay, which would eventually kill the cat. Before the box is opened and the cat’s condition is revealed, the animal may be considered both alive and dead simultaneously. This uncertainty is a fundamental principle of quantum mechanics.

“The quantum mechanical nature of the particle means that it exists in multiple states at the same time. This quantum aspect is known as superposition. That is, until we measure the particle, at which point it collapses into a definite state. Superposition is a key principle that lies at the very heart of quantum technologies,” says Venkata Kamalakar Mutta.

Quantum-mechanical tunnelling observed

An example of a quantum-mechanical phenomenon is tunnelling, in which a particle can tunnel through an insulating barrier even if it lacks sufficient energy to overcome it. This year’s Nobel Prize winners in physics conducted tunnelling experiments in the 1980s using superconductors, materials that conduct electricity with no electrical resistance when cooled below a critical temperature.

“We always have to take the tunnel effect into account in our devices. When we measure the electric current that passes through atomically thin insulating barriers, we routinely observe quantum-mechanical tunnelling at room temperature,” says Venkata Kamalakar Mutta.

Another fundamental quantum property is the electron’s spin. It’s the smallest possible magnet and is responsible for magnetism in materials. This property underpins today's compact computer memories, high-density memory storage, and cloud storage technologies. The spin can point ‘up’ or ‘down’ like a tiny magnetic pole, yet it can also exist in a quantum combination of both, explains Venkata Kamalakar Mutta.

“In our work, we observe how these spin states flow and transform in devices made from atomically thin materials, and we have pioneered several key advances. For example, we pioneered long-distance transport of spin information and controlled ultrafast spin phenomena, with the potential to enable faster memory and logic devices in energy-efficient intelligent electronics. Because individual spins obey the superposition principle, they can even serve as quantum bits or qubits in quantum computers.”

Record-low temperatures reveal quantum particles

With the new dilution refrigerator ELSA, Venkata Kamalakar Mutta sees great prospects for advanced discoveries at the QMD lab. To reach the lowest temperature and study quantum phenomena, a mixture of Helium-3 and Helium-4, two Helium isotopes, is fed into the refrigerator from a container. At the point of spontaneous phase separation, the temperature drops to below 1 Kelvin, even down to 0.01 Kelvin.

“Previously, we were able to cool our systems to about 1.5 Kelvin. With the dilution refrigerator, we can now reach 0.01 K, which is approximately -273 °C and close to absolute zero. At these temperatures, atoms become almost still, and electrons begin to interact in ways that reveal new quantum behaviour.”

The research group’s expertise in atomically thin quantum materials and spin phenomena provides optimal conditions for discovering new states of matter that involve electron and spin interactions. ELSA has a unique triaxial magnetic field, meaning that researchers can apply a high magnetic field in any direction, he adds.

“The explorations can lead to significant advances in new energy-efficient technologies such as superconductors and spin-logic devices that can fundamentally alter computer, sensor, and artificial intelligence hardware. Quantum computers are the most visible applications of quantum technologies. Quantum simulators and quantum sensors are equally promising areas,” says Venkata Kamalakar Mutta.

“But the truth is that we are still at an early stage. To build the second generation of quantum technologies that can genuinely benefit society, we need a complete and reliable understanding of how these quantum systems behave.”

Anneli Björkman