Mika A. Sillanpää: ‘Having a couple of little black holes in the lab would be tremendously helpful’

From sidestepping the Heisenberg uncertainty principle to demonstrating quantum gravity, Aalto Professor has a habit of advancing boundaries in quantum physics
Mika Sillanpää uses a screwdriver on a piece of equipment.
Professor Mika A. Sillanpää was promoted to full professor at the Department of Applied Physics in July 2023.

The career of Aalto University Professor Mika A. Sillanpää can be characterized as a series of breakthrough accomplishments in the esoteric arena of quantum physics.

His research challenges conventional thought. Sillanpää was the first in the world to connect two superconducting qubits via a quantum bus into a quantum superposition state. He has proven that quantum entanglement can be achieved in the macroscale, simultaneously showing how the Heisenberg uncertainty principle can be circumvented.

More recently, Sillanpää has set out to demonstrate quantum gravity, which would effectively unify quantum mechanics and Einstein’s theory of general relativity—a task with significant implications, but formidable experimental challenges.

But Sillanpää has not been one to shy away from challenges in the past. Cautioning against overhyping the flashy concepts behind new quantum technology, Sillanpää said it is necessary to prioritize this type of pioneering, fundamental research.

‘Similar to nanotechnology in the early 2000s, the portrayal of quantum technology in popular media, specifically quantum computers, contains aspects of sensationalism,’ Sillanpää says. ‘There will be useful quantum computers. The next big task for us physicists in fundamental research is merging quantum mechanics with general relativity.’

And now, he will be able to continue his research with a new title: Sillanpää was promoted to full professor at Aalto University in July.

GUANTUM project

Two tiny gold spheres lay on opposing sides of a thin membrane. Measuring a mere 0.5 millimeters in diameter and weighing one milligram each, these spheres could be the catalyst for demonstrating gravitation at the quantum level.

‘Experimentally, it is exceedingly difficult. Having a couple of little black holes in the lab would be tremendously helpful,’ Sillanpää says. ‘Seeing that black holes are not yet commercially available, we have to work with what we have.’

Comparatively, the smallest scale that gravitational influences have been measured is roughly 100 times the mass of the spheres in Sillanpää’s experiments. Even then, the motion was not governed by quantum mechanics, which is the primary focus of the GUANTUM project.

‘On paper, it should be doable, and I believe it can be accomplished in five years,’ Sillanpää says. ‘But we are now taking the first steps towards demonstrating true quantum gravity—a concept that may not be fully realized in my lifetime.’

This is the work that has earned Sillanpää the European Research Council’s advanced grant of €2.5 million. As part of the research, the gold spheres will act as sensitive oscillators in a quantum-mechanical state. It is an extremely closed system where phenomena unseen in classical physics may occur. At the same time, they will observe the very small gravitational forces, which cause the gold spheres to be attracted toward each other.

Continuing work at Aalto

While not busy with the GUANTUM project, Sillanpää leads the Quantum Nanomechanics research group, which, besides the main focus on fundamental research, has been hard at work developing quantum mechanical devices—a product of their research that has wide-ranging applications in the greater field of quantum technology.

Having begun his physics professorship at Aalto in 2012, Sillanpää has hands-on experience with much of the growing body of research infrastructure housed under OtaNano, which is paramount for he and his team to be able to conduct necessary experiments.

‘The Otanano equipment is absolutely critical for our research; we use almost nothing else,’ Sillanpää says. ‘Between the clean rooms and the cryostats, this essential technology enables us to conduct this very important fundamental research.’

Operated by Aalto University and VTT, OtaNano is comprised of the Low Temperature Laboratory, Micronova and the Nanomicroscopy Center. The OtaNano research infrastructure houses comprehensive micro- and nanofabrication facilities in clean-room environments, high-resolution imaging and characterization equipment, and state-of-the-art experimental facilities, including ultra-low temperature possibilities.

More on Sillanpää's research

The highly competed ERC Advanced Grant, awarded to leading top researchers, is the third ERC grant won by Professor Mika A. Sillanpää. In 2009, he received the ERC Starting Grant targeted at talented young researchers and, in 2013, he was awarded the ERC Consolidator Grant intended for top researchers establishing their careers. Picture: Aalto University.

Physicist Mika A. Sillanpää wins a multi-million euro research grant to support work reconciling quantum mechanics and general relativity

The team is trying to solve a hundred-year-old mystery of physics with the help of small gold spheres and extremely low temperatures. The observation of tiny gravitational forces between vibrating spheres may solve the mystery.

The drumheads exhibit a collective quantum motion. Picture: Juha Juvonen.

Aalto researchers awarded Physics World Breakthrough of the Year for macroscopic quantum entanglement

Aalto University Professor Mika A. Sillanpää, his team and collaborators at the University of New South Wales in Canberra, Australia, have won the Physics World 2021 Breakthrough of the Year. The prize was awarded for establishing quantum entanglement between a pair of macroscopic drumheads – two mechanical resonators that were tiny but still much larger than the subatomic particles that are usually entangled. The award has previously been given for the first direct observation of a black hole and for the detection of gravitational waves, which also received a Nobel Prize.

An illustration of the 15-micrometre-wide drumheads prepared on silicon chips used in the experiment. The drumheads vibrate at a high ultrasound frequency, and the peculiar quantum state predicted by Einstein was created from the vibrations. Image: Aalto University / Petja Hyttinen & Olli Hanhirova, ARKH Architects.

Quantum Nanomechanics

The NEMS group focuses on studies of micro- and nanomechanical resonators near the quantum ground state of moving objects.

Department of Applied Physics
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