A CNOT gate between multiphoton qubits encoded in two cavities.

Area of Science:

• Quantum Computing
• Quantum Information Science
• Quantum Error Correction

Background:

• Entangling gates are essential for quantum algorithms but are complex for logical qubits.
• Existing methods typically encode logical qubits in multiple two-level systems, hindering gate implementation.
• High-dimensional encoding offers a promising alternative for robust quantum information processing.

Purpose of the Study:

• To realize a controlled NOT (CNOT) gate between two multiphoton qubits.
• To demonstrate a novel approach for encoding qubits in high-dimensional systems.
• To advance the development of universal algorithms on error-corrected logical qubits.

Main Methods:

• Encoding a qubit in the high-dimensional space of a single microwave cavity mode.
• Coupling two encoded qubits using a transmon.
• Applying the CNOT gate via RF-pumped transmon within 190 nanoseconds.

Main Results:

• Successful realization of a CNOT gate between two multiphoton qubits.
• Gate operation time (190 ns) is two orders of magnitude shorter than transmon decoherence time.
• Achieved high-fidelity gate operation, crucial for quantum error correction.

Conclusions:

• This work presents a significant step towards universal quantum computation.
• The demonstrated high-fidelity entangling gate on high-dimensional qubits paves the way for error-corrected logical qubits.
• This approach simplifies the implementation of essential quantum gates for advanced algorithms.