Quantum riddle solved? How solid neon qubits could change computing forever

The new research probes the electron-in-solid-neon qubit, revealing that tiny bumps on solid neon surfaces create stable quantum states, enabling precise manipulation. This research, supported by multiple foundations, highlights the importance of optimizing the fabrication of the cube, bringing us closer to practical quantum computing solutions.

Recent research has advanced the development of solid electron-in-neon qubits, revealing key insights that improve quantum computing extending the coherence times in the qubit and optimizing their design.

Quantum computers have the potential to be revolutionary tools for their ability to perform calculations that would take classical computers many years to solve.

But to make an effective quantum computer, you need a reliable quantum bit, or qubit, that can exist in a simultaneous state of 0 or 1 for a long enough period, known as its coherence time.

A promising approach is to trap a single electron on a solid neon surface, called an electron-on-solid-neon qubit. A study led by Professor Wei Guo of the FAMU-FSU College of Engineering that was published in Physical review papers shows new insight into the quantum state that describes the state of electrons in such a qubit, information that could help engineers build this innovative technology.

A diagram of a solid electron-in-neon quantum bit. Credit: Courtesy of Wei Guo

Quantum state dynamics and qubit design

Guo’s team found that small bumps on the surface of solid neon in the cube can naturally bind electrons, which creates ring-like quantum states of these electrons. The quantum state refers to the various properties of an electron, such as position, momentum, and other characteristics, before they are measured. When the bumps are of a certain size, the electron’s transition energy—the amount of energy required for an electron to move from one quantum ring state to another—matches the energy of microwave photons, another elementary particle.

Wei Guo, professor in the Department of Mechanical Engineering in the FAMU-FSU College of Engineering. Credit: Mark Wallheiser/FAMU-FSU College of Engineering

This extension allows the controlled manipulation of the electron, which is needed for quantum computing.

“This work significantly advances our understanding of the electron trapping mechanism in a promising quantum computing platform,” Guo said. “It not only elucidates strange experimental observations, but also provides essential insights into the design, optimization and control of solid-state electron-on-neon qubits.”

Previous work by Guo and co-workers demonstrated the viability of a solid-state single-electron qubit platform using electrons trapped in solid neon. Recent research demonstrated coherence times of up to 0.1 millisecond, or 100 times longer than the typical coherence time of 1 microsecond for conventional semiconductor- and superconductor-based loading qubits.

Coherence time determines how long a quantum system can maintain a superposition state—the system’s ability to be in multiple states at the same time while being measured, which is a characteristic that gives quantum computers their unique capabilities.

Optimizing Qubit performance

The extended coherence time of the electron-in-solid neon qubit can be attributed to the inertness and purity of solid neon. This qubit system also addresses the issue of liquid surface vibrations, a problem inherent in the more widely studied electron-in-liquid-helium qubit. The present research provides essential insights for further optimization of the solid electron-in-neon qubit.

A crucial part of this optimization is creating qubits that are smooth over most of the solid neon surface, but have just the right size bumps where they are needed. Designers want minimal, naturally occurring bumps on surfaces that attract destructive electrical charge to the background. At the same time, the deliberate fabrication of appropriately sized bumps inside the microwave resonator in the qubit improves the ability to trap electrons.

“This research highlights the critical need for further study of how different conditions affect neon qubit production,” Guo said. “The temperatures and pressure of the neon injection affect the final product of the qubit. The more control we have over this process, the more precise we can build and the closer we get to a quantum computer that can solve currently unmanageable calculations.”

Reference: “Single-electron qubits based on quantum ring states on solid neon surfaces” by Toshiaki Kanai, Dafei Jin and Wei Guo, 18 Jun 2024, Physical review papers.
DOI: 10.1103/PhysRevLett.132.250603

Co-authors on the paper were Toshiaki Kanai, a former graduate student in FSU’s Department of Physics, and Dafei Jin, an associate professor at the University of Notre Dame.

The research was supported by the National Science Foundation, the Gordon and Betty Moore Foundation, and the Air Force Office of Scientific Research.