Scientists trap molecules to perform quantum operations, a quantum leap

Amazing stuff!

Harvard University wrongly claims: "Molecules haven’t been used in quantum computing ... “As a field we have been trying to do this for 20 years,” said senior co-author Kang-Kuen Ni, Theodore William Richards Professor of Chemistry and professor of physics. “And we’ve finally been able to do it!” ..."

I blogged here in early December 2023 about similar research at Princeton University.

"... This feat was accomplished by using ultra-cold polar molecules as qubits ...

The researchers started by trapping sodium-cesium (NaCs) molecules with optical tweezers in a stable and extremely cold environment. The electric dipole-dipole (or positive-negative) interactions between the molecules were then used to perform a quantum operation. By carefully controlling how the molecules rotated with respect to one another, the team managed to entangle two molecules, creating a quantum state known as a two-qubit Bell state with 94 percent accuracy. ..."

From the abstract:

"Quantum computation and simulation rely on long-lived qubits with controllable interactions. Trapped polar molecules have been proposed as a promising quantum computing platform, offering scalability and single-particle addressability while still leveraging inherent complexity and strong couplings of molecules. Recent progress in the single quantum state preparation and coherence of the hyperfine-rotational states of individually trapped molecules allows them to serve as promising qubits, with intermolecular dipolar interactions creating entanglement.

However, universal two-qubit gates have not been demonstrated with molecules. Here we harness intrinsic molecular resources to implement a two-qubit iSWAP gate using individually trapped X1Σ+ NaCs molecules. By allowing the molecules to interact for 664 μs at a distance of 1.9 μm, we create a maximally entangled Bell state with a fidelity of 94(3)% in trials in which both molecules are present. Using motion–rotation coupling, we measure residual excitation of the lowest few motional states along the axial trapping direction and find them to be the primary source of decoherence.

Finally, we identify two non-interacting hyperfine states within the ground rotational level in which we encode a qubit. The interaction is toggled by transferring between interacting and non-interacting states to realize an iSWAP gate. We verify the gate performance by measuring its logical truth table."

Harvard scientists trap molecules to perform quantum operations — Harvard Gazette "Trapping molecules for use in systems may help make ultra-high-speed experimental technology even faster"

Entanglement and iSWAP gate between molecular qubits (no public accesss)