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Quantum computers simulate largest protein yet with 12,000 atoms | Chemistry World
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New record set by quantum computing as it models its largest protein yet
By Kira Welter2026-05-18T13:30:00+01:00
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A new hybrid workflow involving two IBM quantum computers and two powerful supercomputers has allowed researchers to model two protein–ligand complexes containing up to 12,635 atoms – the largest simulations of biologically meaningful structures ever done with quantum hardware. The team from Cleveland Clinic in the US, Riken in Japan and IBM revealed their results in a preprint that has not been peer reviewed yet.
Source: © IBM and Cleveland Clinic<br>IBM Quantum System One – one of the quantum computers the new work was performed on – at the Cleveland Clinic’s main campus in Cleveland, US
The researchers tested their method on two classic protein–ligand pairs: the digestive enzyme trypsin bound to the inhibitor benzamidine and T4 lysozyme bound to n-butyl-benzene, a model system used to study how small molecules bind inside proteins. ‘Quantum computers are now capable of tackling chemically and biologically relevant molecular systems,’ says Kenneth Merz from Cleveland Clinic and Michigan State University, US, who led the study. But this advancement didn’t come from quantum hardware alone. Instead, Merz and his colleagues split the task between different kinds of machines. First, classical supercomputers broke the large protein–ligand systems into smaller fragments. Then, IBM’s 156-qubit quantum processors calculated the quantum-mechanical behaviours of those pieces in tandem with two classical supercomputers. Finally, the results were put back together on classical systems to construct the full molecular picture.
What is a qubit?
Conventional computers run on binary logic – encoding information as 1s and 0s in various ways such as the orientation of magnetic poles in a computer’s memory chip. These 1s and 0s, or bits, can then be harnessed to perform computational calculations through the use of logic gates. These gates allow a current to flow when the gate’s logic rule is met.
A quantum bit, or qubit, is the quantum computing equivalent of a classical computing bit. Qubits still encode information as 1s or 0s, but encode them in states of a quantum object such as the up or down spin of an atom. However, while a classical bit can only be in one of two states (1 or 0), a qubit can be in a superposition of states, which effectively allows the two states to be mixed in any proportion. This means quantum computers should, in theory, be able to handle information more efficiently.
This potential has theoretical chemists excited because using a quantum object to model other quantum objects (such as atoms and electrons) should be much more efficient. Quantum computing therefore enables us to simulate molecules without having to make a compromise between accuracy and computational cost that is typically required when trying to simulate molecules with a classical computer. (For a more complete discussion of quantum computing examining the limitations and necessary simplications required to explain the concept we have a feature on the topic.)
‘This is a so-called quantum centric supercomputing model of computation (QCSC),’ explains Merz. ‘Rather than solving the entire problem at once, which is currently impossible both on quantum and classical hardware, we break down the problem into smaller, readily solvable sub-problems which can...