Researchers at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory have developed a faster simulation approach for diamond-based quantum materials. By treating atomic defect clusters as isolated molecules, the method identifies promising boron and oxygen-based qubits that function at room temperature.
Diamond-based materials are drawing attention because they can maintain stable quantum states at room temperature, unlike many quantum technologies that require extreme cooling. Nestled on Princeton University’s Forrestal Campus in Plainsboro, New Jersey, the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) conducts research that ignites innovation across sustainability science, quantum materials and devices, nanoscale fabrication, and fusion energy. Although pure carbon diamond is unsuited for data storage and processing on its own, introducing nitrogen through a precise process grants the material characteristics potentially well-suited for quantum sensors and computers, often giving it a pink hue.
Quantum computers and sensors rely on defects—such as a carbon atom missing from its usual spot, a different kind of atom taking its place, or both—to form the clusters of atoms closest to a defect that make up the fundamental information processing unit known as a qubit.
Carving Out Atomic Clusters to Speed Up Qubits
Simulating these atomic defects has long posed a computational nightmare.
By treating the isolated cluster as an isolated molecule, researchers can apply highly accurate tools that chemists have been using for decades to study simple compounds. Because we're treating the qubits as molecules, the cost of calculating these defects is equivalent to the cost of just modeling a simple molecule,
Martirez said, adding that This method really opened the floodgates
in terms of how qubits can be assessed. Using the new approach, researchers can simulate how qubits respond to light and microwave pulses far faster than ever before.
Scientists Use Lasers and Microwaves to Read Qubits
Scientists shine laser light on qubits and pulse microwaves at them to read back information stored within. Traditional investigations into quantum diamond frequently focus on the nitrogen-vacancy defect, characterized by a nitrogen atom substituting for a carbon atom adjacent to an unoccupied lattice site where a carbon atom would normally reside. Exposing this specific type of qubit to laser light causes it to radiate red light when occupying a distinct quantum state.
“One could imagine, then, combining different qubits of different responses, so you can basically probe one qubit but not the other,”
Mark Martirez, staff research scientist at PPPL
This chemical perspective challenges the traditional view of diamond-based qubits as purely a physics problem. But it's not just physicists who should be participating in this research,
Martirez noted. Chemists have decades of developed intuition about chemical systems that could be easily translated into understanding defects in solids as well.
Implications for Quantum Chemistry and Future Industries
Fully understanding the chemistry of qubits could transform the concept of what a qubit structure should be, enabling scientists to design and build qubits the way a chemist designs custom medications or other custom molecules for specific purposes. The broader application of this research extends well beyond hardware development. A practical multi-qubit system would vastly improve the level of accuracy of quantum chemistry calculations.
“When Martirez thinks about the future of his field, he said it’s interesting to note that quantum chemistry may help develop tools to ‘enrich itself’ in the decades to come.”
Mark Martirez, staff research scientist at PPPL
The Department of Energy’s Office of Science serves as the nation’s single largest supporter of basic research in the physical sciences.