Characterization of a two-transmon processor with individual single-shot qubit readout

Area of Science:

• Quantum Computing
• Superconducting Circuits
• Quantum Information Science

Background:

• Superconducting qubits are promising candidates for quantum computation.
• Implementing high-fidelity two-qubit gates is crucial for scalable quantum processors.

Purpose of the Study:

• To characterize a two-qubit processor using tunable transmon qubits.
• To demonstrate the performance of a fixed capacitive coupling for two-qubit gates.
• To verify quantum entanglement and measure gate fidelity.

Main Methods:

• Utilized two capacitively coupled tunable superconducting transmon qubits.
• Implemented nondestructive single-shot readout for each qubit.
• Employed state tomography to reconstruct two-qubit register dynamics.
• Applied quantum process tomography to measure gate fidelity.

Main Results:

• Achieved a sqrt[iSWAP] two-qubit gate with fixed capacitive coupling.
• Observed a violation of the Bell inequality by 22 standard deviations (post-readout error correction).
• Measured a 90% gate fidelity for the two-qubit operation.

Conclusions:

• The characterized two-qubit processor shows high performance for quantum operations.
• The results demonstrate the potential of superconducting transmon qubits for building quantum computers.
• The demonstrated entanglement and fidelity are significant steps towards scalable quantum information processing.