Gold clusters mimic atomic spin properties for scalable quantum computing applications

The effectiveness of quantum computers, sensors and other applications is often based on the properties of electrons, including the way they turn. One of the most precise systems for high -performance quantum applications is based on tapping in spin properties of atom electrons trapped in a gas, but these systems are difficult to evolve for use in larger quantum devices such as quantum computers.

Now, a team of researchers from Penn State and the State of Colorado has demonstrated how a gold cluster can imitate these gaseous and trapped atoms, allowing scientists to take advantage of these spin properties in a system that can be easily put on the scale.

“For the first time, we show that the golden nanoclusters have the same key properties as current current methods for quantum information systems,” said Ken Knappenberger, head of the department and professor of chemistry at the Penn State Eberly College of Science and chief of the research team.

“In an exciting way, we can also handle a large property called spin polarization in these clusters, which is generally fixed in a material. These clusters can be easily synthesized in relatively large quantities, which makes this work proof of promising concept that gold clusters could be used to take care of a variety of quantum applications.”

Two articles describing the gold clusters and confirming their spin properties appear in ACS Central Science And The Journal of Physical Chemistry Letters.

“An electron spin not only influences important chemical reactions, but also quantum applications such as calculation and detection,” said Nate Smith, a student graduated in chemistry at the Penn State Eberly College of Science and first author of one of the articles. “The direction that an electron runs and its alignment compared to the other electrons of the system can have a direct impact on the precision and longevity of quantum information systems.”

Just as the earth revolves around its axis, which is tilted with respect to the sun, an electron can revolve around its axis, which can be tilted from its nucleus. But unlike the earth, an electron can turn in the direction of the needles of a watch or in the antihorarous direction. When many electrons in a material run in the same direction and their inclinations are aligned, the electrons are considered correlated and the material would have a high degree of spin polarization.

“Materials with very correlated electrons, with a high degree of spin polarization, can maintain this correlation for a much longer period, and therefore remain accurate longer,” said Smith.

The current advanced system for high precision and a low error in quantum information systems involves trapped atomic ions – atoms with an electrical load – to a gas state. This system allows electrons to be excited at different energy levels, called Rydberg states, which have very specific spin polarizations which can last a long period. It also allows the superposition of electrons, with electrons existing simultaneously in several states until it is measured, which is a key property for quantum systems.

“These trapped gas ions are by nature diluted, which makes them very difficult to evolve,” said Knapnberger. “The condensed phase required for a solid material, by definition, brings together atoms, losing this diluted nature. Thus, the scaling provides all the right electronic ingredients, but these systems become very sensitive to environmental interference.

“The environment is essentially blurring all the information you have coded in the system, so that the error rate becomes very high. In this study, we have found that gold clusters can imitate all the best properties of gas ions trapped with the benefit of scalability.”

Scientists have greatly studied gold nanostructures for their potential use in optical technology, detection, therapeutics and to accelerate chemical reactions, but we know less about their magnetic and dependent properties of the spin. In current studies, researchers have specifically explored the clusters protected by monocouche, which have a gold nucleus and are surrounded by other molecules called ligands. Researchers can accurately control the construction of these clusters and can synthesize relatively large quantities at the same time.

“These clusters are called super atoms, because their electronic character is like that of an atom, and now we know that their spin properties are also similar,” said Smith. “We have identified 19 distinctive and unique Rydberg polarized states that imitate the super positions that we could do in the diluted ions in the sparkled spat.

The researchers determined the spin polarization of gold clusters using a similar method used with traditional atoms. While a type of gold cluster had a spin polarization of 7%, a cluster with a different ligand approached a 40%spin polarization, which, according to Knapnberger, is competitive with some of the main two -dimensional quantum materials.

“This tells us that the electron’s spin properties are intimately linked to the vibrations of ligands,” said Knapnberger. “Traditionally, quantum materials have a fixed spin polarization value which cannot be considerably modified, but our results suggest that we can modify the ligand of these gold clusters to largely adjust this property.”

The research team plans to explore how different structures in ligands have an impact on spin polarization and how they could be manipulated to refine spin properties.

“The quantum domain is generally dominated by researchers in physics and materials science, and here we see the opportunity for chemists to use our summary skills to design materials with tinnable results,” said Knapnberger. “This is a new border in quantum information science.”

In addition to Smith and Knapnberger, the research team includes Juniper Foxley, a graduate in chemistry at Penn State; Patrick Herbert, who obtained a doctorate in chemistry in Penn State in 2019; Jane Knappenberger, researcher from the Penn State Eberly College of Science; And Marcus Tofanelli and Christopher Ackerson in the state of Colorado.