Two-Qubit EIT Gate Protocol
We have demonstrated the UK’s first neutral atom quantum gate using a novel protocol based on electromagnetically induced transparency (EIT) originally proposed by M. Müller, I. Lesanovsky and P. Zoller back in 2008, with our results published in Phys. Rev. Lett. 129, 200501 (2022).
EIT gate protocol (a) Control and target qubits in individual traps (b) Excitation pulse sequence (c) If the control qubit is in state |0>, the EIT condition on the target qubit prevents transfer whilst (d) if the control qubit is in |1> it is Rydberg excited, with interactions breaking the EIT condition and the target undergoes a Raman transition to implement a native CNOT gate.
We achieved a corrected CNOT gate fidelity of 0.82(6), mainly limited by available laser power, and used this gate to prepare a Bell state on two qubits.
EIT gate results (a) Raw and (b) Corrected gate matrices.
Bell State Preparation (a) Population and (b) Parity Oscillation of Bell states prepared using EIT gate protocol.
This provides a scalable gate protocol capable of performing a native CNOT gate and maps to CNOTN gates with N targets for stabiliser measurements in quantum error correction, for which we proposed with experimental upgrades including performing excitation via the inverted 7P1/2 transition to reach intrinsic fidelities F>0.998.
For more details see our paper Phys. Rev. Lett. 129, 200501 (2022).