Transverse Mode-Encoded Quantum Gate on a Silicon Photonic Chip

Area of Science:

• Quantum Information Science
• Integrated Photonics
• Quantum Computing

Background:

• Orthogonal transverse modes in photonic integrated circuits offer a flexible degree of freedom (d.o.f.) for enhanced communication capabilities in classical and quantum information processing.
• Developing large-scale on-chip multimode quantum systems necessitates a transverse mode-encoded controlled-NOT (CNOT) gate.

Purpose of the Study:

• To demonstrate the first multimode implementation of a 2-qubit quantum gate using transverse mode encoding.
• To establish the feasibility of using novel transverse mode-dependent components for quantum operations.

Main Methods:

• Development of a transverse mode-dependent directional coupler and attenuator.
• Implementation of a 2-qubit quantum gate utilizing transverse mode encoding.
• Characterization of the gate's performance through quantum nonlocality verification and quantum process tomography.

Main Results:

• Demonstration of the first multimode implementation of a 2-qubit quantum gate.
• Achieved an average entanglement fidelity of 0.89±0.02 for two separated transverse mode qubits.
• Verified quantum nonlocality with 10 standard deviations of violations.
• Obtained a gate fidelity of 0.82±0.01 via quantum process tomography.

Conclusions:

• The demonstrated multimode CNOT gate is a significant advancement for transverse mode-encoded quantum operations.
• This work enables the construction of large-scale multimode multi-d.o.f.s quantum systems.
• Paves the way for universal quantum operations in integrated photonic circuits.