Researchers Achieve Chemical Accuracy Using Quantum Error Mitigation

Chemical accuracy, defined as an error threshold of approximately one point five milliHartree, has now been achieved in calculating molecular potential energy surfaces through a new error mitigation technique. Researchers from several Danish and Israeli institutions employed QESEM, a characterisation-based method, on’s Aachen quantum processor to determine the ground-state energies of water molecules with improved precision. An improved error reduction method has successfully been applied to calculations performed on current quantum computers.

Using QESEM, a characterisation-based approach that avoids reliance on assumptions about noise, the team achieved chemical accuracy when modelling water molecules; this level of precision is essential for reliable simulations. These results demonstrate it is possible to obtain meaningful potential energy surfaces from today’s quantum processors despite inherent limitations and sampling demands associated with mitigating errors. Researchers from several Danish and Israeli institutions have demonstrated an error reduction technique capable of achieving chemical accuracy, approximately one point five milliHartree, when calculating molecular potential energy surfaces.

They employed QESEM, a characterisation-based method akin to a set of tools that correct mistakes made during calculations by meticulously mapping flaws within the quantum computer itself; this avoids reliance on potentially biased assumptions about noise. A potential energy surface is essentially a map illustrating a molecule’s energy at different shapes and configurations, much like contour lines on a topographical map reveal altitude variations.

This work focused on modelling water molecules using’s Aachen quantum processor, highlighting the possibility of obtaining meaningful results from today’s hardware despite its limitations. However, reaching these high levels of precision demands significant computational time; does this sampling overhead represent an insurmountable barrier for tackling more complex chemical problems with current technology.

Quantum Error Suppression Enables Chemical Accuracy On Near Term Hardware

Ground state energy estimations utilising Aachen processor have improved significantly through application of an error reduction technique called QESEM. Previously around 500 milliHartree off target, these calculations now fall within chemical accuracy, approximately 1.5 milliHartree. Such precision represents a key error threshold for accurately modelling molecular behaviour and was previously unattainable on near-term quantum hardware; existing methods often relied on assumptions about noise which introduced bias into the results. The team demonstrated that this characterisation-based method systematically improves outcomes as computational demands increase, currently matching or exceeding performance reported in other published studies.

Researchers from several European institutions and Israel have shown improvements in calculating molecular energies with QESEM on Aachen processor. An eight-qubit system representing water molecules was employed alongside a classically optimised calculation method known as a perfect-pairing tiled unitary product state ansatz to map the molecule’s energy levels; this approach systematically enhances accuracy with increased computational effort. Benchmarking at both loose (0.1 Hartree) and tight (0.01 Hartree) targets revealed that tighter precision demands sharply more processing time on the quantum hardware, specifically requiring greater numbers of ‘shots’, which are individual runs of the computation.

Quantum computation nears chemical accuracy in modelling simple molecular energetics

Establishing accurate molecular potential energy surfaces is fundamental for modelling chemical behaviour, and this work demonstrates progress towards that goal using near-term quantum computers despite their inherent limitations. The successful application of QESEM shows obtaining quantitatively meaningful potential energy surfaces from existing quantum hardware is now possible; a potential energy surface maps a molecule’s energy across different configurations and is vital to understanding how molecules behave chemically.

Aachen facility has successfully applied an unbiased error mitigation technique, QESEM, to calculate energies for water with accuracy approaching “chemical accuracy”, roughly one and half milli-Hartree units of difference from precise calculations. However, substantial computational demands arise as precision targets increase, raising questions about scalability beyond these initial demonstrations involving relatively small molecules and simplified electronic configurations.

The research team calculated the ground-state potential energy surface of the symmetrically-stretched water molecule using quantum hardware and achieved results within approximately 100 milliHartree of a reference calculation. This demonstrates that meaningful molecular energetics can be obtained even on noisy near-term quantum computers through application of an unbiased error mitigation technique called QESEM. The study used an eight-qubit system with the STO-3G basis set to represent the water molecule’s active space. Researchers found accuracy improved as precision targets were tightened, though this required more computational resources in terms of ‘shots’.

More like this

Quantum Research NewsResearchers Certify High-Speed Randomness from Semiconductor Noise

Quantum Research NewsOkayama University’s quantum superconductor boasts 6.2K transition

Quantum Research NewsNon-Hermitian spin model boosts quantum reservoir computing

Quantum Research NewsResearchers Bound Certification Costs for Bell Tests with Tilted Data