Designer Qubit Breakthrough Opens New, Promising Molecular Chemistry Frontier for Quantum Systems

(By Becky Bracken) Instead of today’s qubits made from typical semi-conductor materials, an interdisciplinary team of physicists and chemists has figured out how to turn specific molecules into qubits, providing a glimpse into a new frontier of flexibility and control over quantum systems using molecular chemistry.
Where a bit can only hold two values, qubits, once put into a state called “superposition” with the use of precision lasers and microwave beams, take on the ability to represent multiple values at the same time, allowing the system to calculate vast possibilities in outcome simultaneously.
Led by chemists Danna Freedman from Northwestern University and David Awschalom from the University of Chicago, (David spoke at IQT’s most recent conference) an interdisciplinary team of researchers has proven molecular chemistry can be used to synthesize molecules and encode quantum information into their “spin” states, they explained in their findings published by the journal Science last November.
According to the report, the researchers used organometallic chromium molecules in their experiments. They used lasers to excite the molecules, then measured the amount of light emitted, giving the team the ability to “read” the molecules. The report also explained they used synthetic chemistry to change the molecule’s optical and magnetic properties, demonstrating the potential for designer-built qubits for specific uses.
“This is a proof-of-concept of a powerful and scalable quantum technology,” said Awschalom, the Liew Family Professor in Molecular Engineering about the findings in Northwestern NOW. “We can harness the techniques of molecular design to create new atomic-scale systems for quantum information science. Bringing these two communities together will broaden interest and has the potential to enhance quantum sensing and computation.”
The result of this breakthrough has created an entirely new field of study, the researchers said.
“Our results open up a new area of synthetic chemistry,” Freedman said. “We demonstrated that synthetic control of symmetry and bonding creates qubits that can be addressed in the same way as defects in semiconductors.”
She adds the team’s “bottom-up approach” and the development of what she calls “designer qubits” are a precursor to the “creation of arrays of readily controllable quantum states, offering the possibility of scalable quantum systems.”
The bottom-up approach is also likely to help systems more easily integrate with existing infrastructure, according to Daniel Laorenza, a graduate student in Freedman’s lab and co-first author of the paper.
“This chemically specific control over the environment around the qubit provides a valuable feature to integrate optically addressable molecular qubits into a wide range of environments.”