One of the most promising uses for quantum computers is to simulate proteins that could help us discover new drugs, but these devices are currently too error-prone for the task. However, two quantum computers have now broken a simulation record – determining the properties of a molecule with 12,635 atoms – with some help from supercomputers. To understand the behaviour of drug molecules, we need to pin down the quantum states and energies of their electrons, which is a quantum problem that can often be solved only approximately on conventional computers. Advertisement A collaboration between researchers at the Cleveland Clinic in Ohio, the US tech firm IBM and the Japanese scientific institute RIKEN has instead turned to quantum computers, which “speak” quantum physics by default. They developed a hybrid approach that combines quantum computers and conventional supercomputers and used it to simulate two unprecedentedly large molecules, with one about 40 times bigger than the past largest molecule simulated using a quantum computer. “This has been a dream of mine, and here we are,” says team member Kenneth Merz at the Cleveland Clinic. The researchers used two IBM Heron quantum computers, one located at RIKEN and one at the Cleveland Clinic, and two supercomputers called Fugaku and Miyabi-G, which are among the most powerful in the world. For the molecules, the team chose two combinations of a protein and a small molecule, or “protein-ligand complexes”, that Merz says are well studied and popular as fundamental examples in biomedical sciences. The team also simulated them in a layer of water, bringing the results closer to mimicking how researchers work with the molecules in the lab. Free newsletter Sign up to The Daily The latest on what’s new in science and why it matters each day. Quantum computers alone currently have limited usefulness