Curator's Take
This article tackles a crucial practical challenge in quantum computing with polar molecules: how the molecules' motion within optical traps affects their ability to serve as qubits. The researchers discovered that this quantized motion creates an asymmetric quantum Rabi model and can cause problematic "trap-dipole resonance" that leads to unwanted population loss, providing important insights for avoiding these pitfalls in molecular quantum systems. Most encouragingly, they demonstrate that despite these motion-related complications, high-fidelity quantum gates including a fast iSWAP gate and an arbitrary controlled-phase gate can still be achieved with polar molecules. This work represents significant progress toward making polar molecule platforms viable for quantum computing, as these systems offer unique advantages like long coherence times and strong controllable interactions through their electric dipole moments.
— Mark Eatherly
Summary
Optically trapped ultracold polar molecules can have multiple long-lived states for coding quantum information, and can exhibit electric dipole-dipole interactions~(DDI) which enables entanglement generation. The general understanding on the quantized motion~(QM) of molecules in the traps is that it causes fluctuation of DDI. Here, we find that the molecular QM can realize an asymmetric quantum Rabi model, which is of specific importance in the study of fundamental physics. The molecular QM can also lead to an exotic trap-dipole resonance, resulting in excess population loss to uncoupled motional states, and, hence, should be avoided in a general quantum control over polar molecules. To examine the impact of QM on quantum computing based on polar molecules, we introduce two gate protocols, a fast iSWAP gate which can be realized by a global microwave pulse of pulse area smaller than $2π$, and a controlled-phase gate with an arbitrary controlled phase, and find that both gates can attain a high fidelity.