Quantum Leap for Chemistry: IBM & Lockheed Martin Combine Quantum & Classical Computing for Accurate Molecular Simulations

Lockheed Martin and IBM researchers have successfully combined quantum computing with high-performance classical computing to accurately model the electronic structure of open-shell molecules, specifically methylene (CH2), a radical species crucial to combustion, atmospheric chemistry, and sensor design. Utilizing the sample-based quantum diagonalization (SQD) technique on an IBM quantum processor with 52 qubits, the team calculated both singlet and triplet states, achieving strong agreement with high-accuracy classical methods for dissociation energies and accurately predicting the singlet-triplet energy gap—marking the first application of SQD to an open-shell system and demonstrating the potential of quantum-centric supercomputing for real-world chemical simulations.

Researchers successfully calculated both singlet and triplet states, including dissociation energies and energy gaps, utilising 52 qubits of an IBM quantum processor and executing up to 3,000 two-qubit gates per experiment. This work establishes a new level of credibility for quantum methods when tackling molecules with complex electronic structures, such as radicals and carbenes. Traditional computational chemistry struggles with open-shell molecules, therefore quantum computers offer a valuable tool for simulating reactivity and capturing complex wavefunctions. The ability to accurately model the dissociation of the CH bond in CH₂ and the electronic transitions between singlet and triplet states improves understanding of how these species behave in real-world conditions.

The study applied the SQD (Spin-Qubit Dynamics) method to compute the electronic properties of methylene’s singlet and triplet states within IBM’s quantum-centric supercomputing framework. This hybrid architecture couples quantum processors with classical compute resources, enabling scalable molecular simulations. Results benchmarked against high-accuracy classical methods – Selected Configuration Interaction (SCI) – demonstrate strong agreement for singlet dissociation energy, achieving accuracy within a few milli Hartrees of the SCI reference, and consistent triplet energies near equilibrium geometries.

Radical molecules are key components in aerospace, combustion chemistry, and sensor design, and accurate modelling can lead to better predictive models, more efficient chemical engines, and new sensing technologies capable of detecting minute traces of reactive species. Predicting the behaviour of these molecules is vital for developing better models of combustion emissions, propulsion systems, and chemical sensing technologies, as they emerge during bond-breaking reactions.