High-rate entanglement generation between ions in a multispecies ion trap using photonic interconnects*

Long chains of trapped ions are a leading platform for quantum information processing, but as chains grow longer their control suffers from spectral crowding and excess motional heating. One method to increase the computational power available is the use of photonic interconnects to entangle ions in separate traps. Toward this goal, we have built an ion trap system with two high numerical aperture (NA=0.8) in-vacuum objectives, achieving the highest free-space collection efficiency of photons from an ion. We trap two ¹³⁸Ba⁺ ions and generate entanglement between them using photons, demonstrating the efficacy of its photonic interconnects. To increase the entanglement generation rate, we co-trap ¹⁷¹Yb⁺ to sympathetically cool the barium ions. We achieve the highest entanglement generation rate between two qubits entangled via photonic interconnects.