Announcing the birth of unique analog quantum processor QUIONE

Quantum physics requires high-precision sensing technology to delve into the microscopic properties of materials. Judging from the recent emergence of analog quantum processors, quantum gas microscopy has proven to be a powerful tool for understanding quantum systems at the atomic level. These devices produce images of quantum gases with very high resolution: they allow the detection of individual atoms.

Now, ICFO researchers (Barcelona, ​​Spain) Sandra Buob, Jonatan Höschele, Dr. Vasiliy Makhalov and Dr. Antonio Rubio-Abadal, led by ICREA Professor Leticia Tarruell at ICFO, explain how they built their own quantum gas microscope called QUIONE is named after the Greek snow goddess of microscopes. The team’s quantum gas microscope is the only one in the world that images single atoms of strontium quantum gas, and the first of its kind in Spain.

The team’s research is published in the journal PRX Quantum.

In addition to impactful images that can distinguish individual atoms, QUIONE targets quantum simulations. As Professor Tharoor explains, “Quantum simulations can be used to reduce very complex systems into simpler models to understand open questions that currently cannot be answered by computers, such as why certain materials perform better even at relatively high temperatures. It can also conduct electricity without any loss.

The singularity of the experiment is that the team successfully brought the strontium gas into a quantum state, placed it in an optical lattice where atoms can interact through collisions, and then applied single-atom imaging technology. Together, these three components make ICFO’s strontium quantum gas microscope unique.

Why strontium?

Until now, these microscopy devices have relied on basic atoms such as lithium and potassium, which have simpler spectral properties than alkaline earth atoms such as strontium. This means that strontium provided more of the component in these experiments.

In fact, in recent years, strontium’s unique properties have made it a very popular element for applications in quantum computing and quantum simulations. For example, clouds of strontium atoms could be used as atomic quantum processors, which can solve problems beyond the capabilities of current classical computers.

All in all, ICFO researchers saw so much potential in strontium quantum simulations that they began building their own quantum gas microscope. This is how QUIONE was born.

QUIONE, a quantum simulator of real crystals

To do this, the team first lowered the temperature of the strontium gas. They used the power of several laser beams to slow down the atoms to the point where they were almost motionless, and their temperature dropped to almost absolute zero in just a few milliseconds. Thereafter, the laws of quantum mechanics governed their behavior, and atoms exhibited new characteristics such as quantum superposition and entanglement.

Then, with the help of special lasers, the researchers activated the optical lattice, which arranged the atoms into a grid along the space.

“You can think of it like an egg carton, where the various positions are actually where you put the eggs. But we replace the eggs with atoms and the cartons with optical lattices,” explains first author Buob, of the article.

The atoms in the egg cup interact with each other, sometimes traveling through quantum tunnels to move from one place to another. Quantum dynamics between atoms simulates the quantum dynamics of electrons in certain materials. Studying these systems can therefore reveal the complex behavior of certain materials, a key idea in quantum simulations.

Once the gas and optical lattice were prepared, the researchers took images with a microscope, ultimately allowing them to view the strontium quantum gas atom by atom. By this point, QUIONE’s build had been a success, but its creators wanted more from it.

So, in addition to photos, they also took videos of the atoms and were able to observe that, while the atoms were supposed to remain stationary during the imaging process, they sometimes jumped to nearby lattice positions. Quantum tunneling could explain this.

“Atoms ‘jump’ from one location to another. This is a very beautiful thing because we are literally witnessing a direct manifestation of their inherent quantum behavior,” Buob said.

Finally, the research team used quantum gas microscopy to confirm that strontium gas is a superfluid, a quantum phase of matter that flows inviscidly.

“We suddenly turned off the lattice laser, causing the atoms to expand in space and interfere with each other. Due to the wave-particle duality of the atoms in the superfluid, this created an interference pattern. When our device captured it, we verified that in the sample The wave-particle duality of the atoms, which creates the interference pattern, when our device captures it, we verify the presence of superfluidity in the sample,” explains Dr. Rubio-Abaidal.

“This is a very exciting time for quantum simulations,” Professor Tharoor said. “Now that we have added strontium to the list of available quantum gas microscopes, we may soon be able to simulate more complex and exotic materials. Then, new phases of matter are expected to emerge. And we also expect to gain more computing power The ability to use these machines as simulated quantum computers.