Molecular approach to quantum computing

In a new theoretical study, Caltech physicists have shown how molecules can, in theory, be used to reduce errors in quantum computing. This strategy would involve placing a rotating molecule in "superposition," which means that it would exist in multiple orientations at once. In this illustration, three different molecular orientations are shown at left; the drawing at far right signifies a superposition of these molecular states. Credit: Caltech

Physicists at Caltech have demonstrated the benefits of a lesser-studied approach for quantum computers that relies not on atoms but molecules.

if a quantum computer platform uses qubits made of molecules, the researchers say, the qubit errors are more likely to be prevented than in other quantum platforms.

One concept behind the new research comes from work performed nearly 20 years by scientists who proposed a loophole that would provide a way around a phenomenon called Heisenberg’s uncertainty principle.

The uncertainty principle is a challenge for quantum computers because it implies that the quantum states of the qubits cannot be known well enough to determine whether or not errors have occurred. However, Gottesman, Kitaev, and Preskill then at Caltech figured out that while the exact position and momentum of a particle could not be measured, it was possible to detect very tiny shifts to its position and momentum. These shifts could reveal that an error has occurred, making it possible to push the system back to the correct state. This error-correcting scheme, known as GKP after its discoverers, has recently been implemented in superconducting circuit devices.

This concept is applied to rotating molecules in superposition. If the orientation or angular momentum of the molecule shifts by a small amount, those shifts can be simultaneously corrected. (

The paper has been published in the journal Physical Review X.

Read more.