New research combining experimental and computational approaches provides deeper insights into proton spin contributions from gluons.

Nuclear physicists have been tirelessly exploring the origins of proton spin. A novel approach, merging experimental data with cutting-edge calculations, has now illuminated the spin contributions from gluons—the particles that bind protons. This advancement also sets the stage for three-dimensional imaging of the proton structure.

Joseph Karpie, a postdoctoral associate at the Center for Theoretical and Computational Physics (Theory Center) at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility, led this groundbreaking research.

Researchers at the University of Hong Kong discovered Dirac spinons in the material YCu3-Br, providing evidence of a quantum spin liquid state and potentially advancing applications in quantum computing and high-temperature superconductivity.

Quasiparticles are fascinating entities that arise from collective behavior within materials and can be treated as a group of particles. Specifically, Dirac spinons are anticipated to exhibit unique characteristics similar to Dirac particles in high-energy physics and Dirac electrons in graphene and quantum moiré materials, such as a linear dispersion relation between energy and momentum. However, spin-½ charge-neutral quasiparticles had not been observed in quantum magnets until this work.

‘“To find Dirac spinons in quantum magnets has been the dream of generations of condensed matter physicists; now that we have seen the evidence of them, one can start to think about the countless potential applications of such highly entangled quantum material. Who knows, maybe one-day people will build quantum computers with it, just as people have been doing in the past half-century with silicon,’” said Professor Meng, HKU physicist and one of the corresponding authors of the paper.

Many of today’s quantum devices rely on collections of qubits, also called spins. These quantum bits have only two energy levels, the ‘0’ and the ‘1’. However, unlike classical bits, qubits can exist in superpositions, meaning they can simultaneously be in a combination of the ‘0’ and ‘1’ states. Spins in real devices also interact with light and vibrations known as bosons, greatly complicating calculations.

In a new publication in Physical Review Letters (“Fast quantum state preparation and bath dynamics using non-Gaussian variational Ansatz and quantum optimal control”), researchers in Amsterdam demonstrate a way to describe spin-boson systems and use this to efficiently configure quantum devices in a desired state.

Quantum devices use the quirky behaviour of quantum particles to perform tasks that go beyond what ‘classical’ machines can do, including quantum computing, simulation, quantum sensing, quantum communication and quantum metrology. These devices can take many forms, such as a collection of superconducting circuits, or a lattice of atoms or ions held in place by lasers or electric fields.