Demonstration of two-atom entanglement with ultrafast optical pulses

TL;DR

This paper demonstrates a fast, high-fidelity entanglement of two trapped ion qubits using ultrafast laser pulses, avoiding the need for the Lamb-Dicke regime and enhancing robustness against noise.

Contribution

It introduces a novel ultrafast phase gate scheme for entangling trapped ions without requiring confinement to the Lamb-Dicke regime.

Findings

Achieved 76% Bell-state fidelity with 10 ultrafast pulses.

Generated entanglement at a high rate using 20 ps pulses.

Demonstrated a method scalable to large qubit systems.

Abstract

We demonstrate quantum entanglement of two trapped atomic ion qubits using a sequence of ultrafast laser pulses. Unlike previous demonstrations of entanglement mediated by the Coulomb interaction, this scheme does not require confinement to the Lamb-Dicke regime and can be less sensitive to ambient noise due to its speed. To elucidate the physics of an ultrafast phase gate, we generate a high entanglement rate using just 10 pulses, each of $\sim20$ ps duration, and demonstrate an entangled Bell-state with $(76\pm1)$% fidelity. These results pave the way for entanglement operations within a large collection of qubits by exciting only local modes of motion.