Freezing molecular hydrogen within the crystalline structure of dry ice offers a precise method of controlling its quantum properties, according to a new study from University of Maryland chemical physicists. Researchers discovered that this act of freezing blocks the natural conversion of two of three substates of ortho-H2 to the lower-energy para-H2 state, demonstrating a granular level of quantum manipulation achieved through materials design. “Our paper demonstrates a new way to control quantum behavior using materials design alone,” said Leah Dodson, an assistant professor in UMD’s Department of Chemistry and Biochemistry and the paper’s senior author. This technique has potential implications for more stable hydrogen fuel storage, improved quantum memory, and refining measurements of comet temperatures in deep space.
Dry Ice Crystals Control Hydrogen Nuclear Spin States
Freezing molecular hydrogen within dry ice crystals presents a surprising degree of control over its quantum properties. Researchers at UMD have demonstrated the ability to selectively block the natural conversion between hydrogen’s nuclear spin states. This manipulation isn’t achieved through complex apparatus, but by leveraging the physical environment itself, specifically the crystalline structure of dry ice, and represents a departure from traditional methods reliant on magnetic fields or catalysts. The study, published in Physical Review Letters, details how two of the three substates of ortho-H2 are uniquely shielded from conversion to the lower-energy para-H2 when embedded within the dry ice matrix. The geometry of crystalline dry ice imposes a specific set of constraints on the hydrogen molecules, dictating which quantum transitions are permitted; Nathan McLane, a chemical physics graduate student and lead author, explained that these constraints are “a set of ‘rules’ that H2 has to follow.”
Introducing nitrogen dioxide into the crystal lattice relaxes these rules, allowing all three ortho-H2 substates to convert, highlighting the granular level of control achievable through materials design. This precision is significant because it demonstrates that the surrounding solid directly influences quantum dynamics, a finding that could have implications for diverse fields and also holds promise for improved hydrogen fuel storage and more accurate astronomical measurements of comet temperatures.
Nitrogen Dioxide Modifies Ortho-H2 Conversion Pathways
Researchers at the University of Maryland have demonstrated an unexpected level of control over the quantum behavior of molecular hydrogen, achieved through manipulation of its surrounding crystalline environment. “The big finding is that, depending on what ice we put an H2 molecule into, its quantum dynamics are entirely dependent on the surrounding environment,” McLane said. This ability to manipulate conversion pathways has implications for diverse fields, from energy storage to astronomical measurements, and potentially even quantum computing, establishing foundational rules for protecting quantum states.
We show experimentally that when molecular hydrogen-the simplest molecule-is confined within different molecular crystals, the symmetry of the surrounding solid determines which quantum spin states can interconvert and which remain protected.
Impact on Quantum Memory, Fuel Storage, and Astrochemistry
This granular control, affecting specific substates while leaving others untouched, suggests a level of precision previously unseen in manipulating quantum spin. The implications extend beyond fundamental physics, reaching into practical applications like hydrogen fuel storage, where the U.S. Department of Energy funded this research. By enriching specific nuclear spin states and protecting others, fuel could be stored more stably and efficiently, mitigating heat release during conversion from ortho to para hydrogen; Dodson explained that fuel managers “have to handle that heat safely and efficiently, so they’re incentivized to understand how it gets produced.” This technique offers a new avenue for refining astronomical measurements, particularly in determining the formation temperatures of comets, as NASA currently relies on assumptions about nuclear spin changes that Dodson hopes to validate. Dodson believes this work “is setting out the foundational rules for how quantum states might become protected,” establishing a basis for future applied research in the field.
This work is setting out the foundational rules for how quantum states might become protected.
