New quantum method mimics molecular chemistry efficiently

Researchers have used a single atom to simulate how molecules react to light, marking a milestone in quantum chemistry.

The experiment, carried out by a team at the University of Sydney and published in the Journal of the American Chemical Society on 14 May, could accelerate the path to a quantum advantage, where quantum simulations outperform classical computing methods.

Instead of relying on multiple qubits, the team used a single ytterbium ion confined in a vacuum to mimic the complex interactions within organic molecules such as allene, butatriene and pyrazine.

The molecules react to photons through a series of electron and atomic movements, which are difficult to model using conventional computing when the number of vibrational modes increases.

The researchers encoded electronic excitations into the ion’s internal states and its motion along two directions in the trap, simulating molecular vibrations. By manipulating the ion with lasers, they emulated how the molecules behave after absorbing a photon.

The team then measured changes in the ion’s excited state over time to track the simulation’s progress. The method’s accuracy was validated by comparing results with known behaviours of the molecules.

While these specific molecules can still be simulated with traditional methods, the team believes their hardware-efficient approach could model more complex chemical systems using only a few dozen ions, rather than millions of qubits.

Experts, including quantum chemist Alán Aspuru-Guzik and Duke University’s Kenneth Brown, praised the work as a significant advance in quantum simulation.

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