Demonstration of a quantum logic gate in a cryogenic surface-electrode ion trap

TL;DR

This paper demonstrates a high-fidelity quantum CNOT gate in a cryogenic surface-electrode ion trap, utilizing advanced control techniques to mitigate decoherence and stabilize qubits, advancing quantum computing hardware.

Contribution

It introduces a novel implementation of a quantum CNOT gate in a cryogenic ion trap with improved stabilization and control methods, achieving 91% fidelity.

Findings

Achieved a 91% fidelity in a quantum CNOT gate.

Implemented magnetic field stabilization using superconducting rings.

Suppressed decoherence through cryogenic environment and phase control.

Abstract

We demonstrate quantum control techniques for a single trapped ion in a cryogenic, surface-electrode trap. A narrow optical transition of Sr+ along with the ground and first excited motional states of the harmonic trapping potential form a two-qubit system. The optical qubit transition is susceptible to magnetic field fluctuations, which we stabilize with a simple and compact method using superconducting rings. Decoherence of the motional qubit is suppressed by the cryogenic environment. AC Stark shift correction is accomplished by controlling the laser phase in the pulse sequencer, eliminating the need for an additional laser. Quantum process tomography is implemented on atomic and motional states using conditional pulse sequences. With these techniques we demonstrate a Cirac-Zoller Controlled-NOT gate in a single ion with a mean fidelity of 91(1)%.