Transverse mode-encoded quantum gate on a silicon photonic chip

TL;DR

This paper demonstrates the first on-chip multimode quantum CNOT gate using transverse mode encoding on a silicon photonic chip, enabling scalable quantum information processing with high fidelity and nonlocality verification.

Contribution

It introduces a novel integrated transverse mode-dependent directional coupler and implements a multimode quantum CNOT gate on silicon photonics, advancing scalable quantum systems.

Findings

Achieved a gate fidelity of 0.89 for entangling transverse mode qubits.

Verified quantum nonlocality with 10 standard deviations.

Quantum process tomography yielded a fidelity of 0.82 for the CNOT gate.

Abstract

As an important degree of freedom (DoF) in integrated photonic circuits, the orthogonal transverse mode provides a promising and flexible way to increasing communication capability, for both classical and quantum information processing. To construct large-scale on-chip multimode multi-DoF quantum systems, a transverse mode-encoded controlled-NOT (CNOT) gate is necessary. Here, through design and integrate transverse mode-dependent directional coupler and attenuators on a silicon photonic chip, we demonstrate the first multimode implementation of a two-qubit quantum gate. With the aid of state preparation and analysis parts, we show the ability of the gate to entangle two separated transverse mode qubits with an average fidelity of $0.89\pm0.02$ and the achievement of 10 standard deviations of violations in the quantum nonlocality verification. In addition, a fidelity of $0.82\pm0.01$ was obtained from quantum process tomography used to completely characterize the CNOT gate. Our work paves the way for universal transverse mode-encoded quantum operations and large-scale multimode multi-DoF quantum systems.