Berkeley Lab’s quantum light source aids neuromorphic computing

For more than three decades, the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory has assisted scientists in understanding quantum materials. Through the years, powerful tools at the ALS have helped researchers develop a one-atom-thin magnet and a method for building qubits for quantum computers from 2D metal organic frameworks.

“ALS-U is a very important undertaking for the U.S. synchrotron research community,” says Riccardo Comin, associate professor of physics at the Massachusetts Institute of Technology, as the facility undergoes an upgrade to produce brighter beams of light that will allow researchers to directly measure defects and observe exotic quantum states in situ as they evolve within a billionth of a second at the nanoscale.

Advanced Light Source Drives Quantum Material Discovery

The Advanced Light Source (ALS) will soon enable the study of electron behavior at the nanometer scale, a capability crucial for advancing research into superconductivity and spintronics. The ALS is undergoing an upgrade that will produce more coherent beams of light that are orders of magnitude brighter than today.

The ALS Upgrade will enable X-ray beams focused to less than 25 nanometers, small enough to resolve nanoscale variations in quantum materials that are invisible to current instruments. This capability will allow for exploration of electron coherence at smaller length scales and observation of emergent electronic phases.

The ALS is exploring further upgrades down to less than 10 nm, including a new technique called “Ultimate NanoARPES” that will be sensitive to individual defects in quantum materials like superconducting qubits and exotic metals. The upgraded facility will house FLEXON, a new instrument that will use X-ray photon correlation spectroscopy (XPCS). XPCS will measure nanosecond fluctuations in charge and spin within quantum materials, providing insight into the dynamics of electron behavior.

ARPES instruments, like MAESTRO, have been pivotal in untangling the mechanisms of high-temperature superconductivity and identifying quantum materials with potential for future devices. The facility’s ongoing evolution promises continued advancements in understanding and harnessing the potential of quantum materials.

ARPES Reveals Electronic Structure of Superconducting Materials

Angle-resolved photoemission spectroscopy (ARPES) at the Advanced Light Source (ALS) has long been central to understanding the behavior of electrons in quantum materials, and upcoming upgrades to the facility promise to dramatically expand its capabilities. For over three decades, scientists have utilized ARPES instruments like MAESTRO, the Microscopic and Electronic STRucture Observatory, to map the energy and momentum of electrons, revealing the electronic band structures governing a material’s properties.

This technique has proven pivotal in untangling the complexities of high-temperature superconductivity and topological insulators, providing crucial insights into these quantum phenomena. In 2022, Comin and his team used MAESTRO to identify and measure the velocities of electrons emerging from superconductivity in a Kagome metal, demonstrating the instrument’s current ability to focus beams to 10 micrometers and measure tiny samples or specific regions of a material.

Comin asserts that “MAESTRO at the Advanced Light Source is one of the leading ARPES tools in the world,” adding that “it is an important tool for studying quantum materials, because it gives you a snapshot of where the electrons are on an energy spectrum.” The ALS Upgrade will also improve the energy resolution, flux, and stability of spin-resolved ARPES techniques, which characterize the direction of electron spin, offering a more complete picture of electron behavior. Beyond superconductivity, ARPES at the ALS is also contributing to the development of future spintronic devices.

Recent work by Ming Yi of Rice University utilized spin-resolved ARPES to demonstrate a method for regulating electrons of opposite spins within the 3D structure of crystal compounds, potentially advancing electronics and spintronics. Ultimately, these advancements in ARPES, coupled with the ALS Upgrade, are expected to accelerate the discovery and understanding of new quantum materials with the potential to revolutionize fields ranging from computing to energy.

Spin-Resolved ARPES Advances Next-Gen Spintronic Devices

Frañó’s work centers on replicating the energy efficiency of the human brain in electronic systems, and the upgraded capabilities of the ALS will be critical in understanding electron behavior at the nanoscale, a key challenge in this field. The ALS Upgrade will significantly enhance spin-resolved ARPES techniques, allowing for more precise measurements of electron spin and momentum within materials.

This is particularly important for spintronics, a technology promising faster and more robust devices than current electronics. Controlling these electron movements could yield desirable properties for future electronic and spintronic applications, and the work also supports a quantum theory predicting superconducting properties that could accelerate quantum computation.

Eli Rotenberg, a senior scientist leading the ARPES program at the ALS, notes that the upgraded facility’s brighter, more coherent light will be essential for identifying how specific defects disrupt qubit coherence and for shaping materials at the nanoscale. He said, “The ALS Upgrade’s brighter, more coherent light is critical to seeing how a particular defect spoils coherence in a qubit. It will also allow us to get to smaller length scales and shape how a quantum material works.”

ALS Upgrade Will Resolve Nanoscale Quantum Coherence

This leap in capability stems from the facility’s planned ability to focus X-ray beams to less than 25 nanometers, with further upgrades being explored down to less than 10, revealing nanoscale variations in materials that currently remain hidden. This increased resolution is critical for understanding decoherence, a phenomenon where quantum states collapse, introducing errors in devices like qubits used in quantum computing. Directly measuring the influence of defects causing decoherence has proven difficult, but the upgraded facility promises to overcome this hurdle.

Beyond simply shrinking the beam size, the ALS Upgrade will dramatically enhance the coherence of the emitted light. The impact extends beyond fundamental materials science, directly influencing research into superconductivity and spintronics. This research aims to mimic the brain’s neural networks, potentially creating computers that process information with far greater efficiency and lower energy consumption. The ALS Upgrade will support the development of new techniques for synthesizing quantum materials with enhanced control at the nanoscale.