Crosstalk Suppression in Individually Addressed Two-Qubit Gates in a Trapped-Ion Quantum Computer

Area of Science:

• Quantum Computing
• Atomic Physics
• Quantum Information Science

Background:

• Crosstalk between qubits is a significant error source in quantum computers.
• Spillover of control signals degrades the fidelity of two-qubit entangling gates.

Purpose of the Study:

• To model and actively suppress coherent crosstalk errors in laser-driven trapped-ion systems.
• To demonstrate a novel crosstalk suppression scheme using local qubit control.

Main Methods:

• Modeled coherent crosstalk as a residual Xσ[over ^]_{ϕ} interaction.
• Implemented single-qubit echoing pulses for active error cancellation.
• Applied echoing pulses locally to target qubits.

Main Results:

• Achieved a two-qubit Bell state fidelity of 99.52(6)% with post-gate echoing.
• Obtained a fidelity of 99.37(5)% with echoing applied to each gate.
• Demonstrated a scheme requiring only local control, unlike prior methods.

Conclusions:

• Coherent crosstalk in trapped-ion systems can be effectively canceled by single-qubit echoing pulses.
• The proposed local control scheme significantly enhances two-qubit gate fidelity.
• This technique is broadly applicable to other quantum computing platforms.