Demonstrating two-qubit entangling gates at the quantum speed limit using superconducting qubits

The speed at which quantum entanglement between qubits with short range interactions can be generated is limited by the Lieb-Robinson bound. Introducing longer range interactions relaxes this bound and entanglement can be generated at a faster rate. The speed limit for this has been explicitly found theoretically only for a two-qubit system and under the assumption of negligible single qubit gate time. We have theoretically determined this speed limit for a realistic experimental system. Furthermore, we go on to demonstrate this speed limit experimentally using two superconducting transmon qubits. This development has important implications for large scale quantum computing.