Integrated photonic quantum gates for polarization qubits

TL;DR

This paper reports the first integrated photonic CNOT gate for polarization qubits, enabling advanced quantum information processing with high fidelity and full device characterization.

Contribution

It introduces a novel integrated photonic CNOT gate for polarization qubits using femtosecond laser writing, a significant step forward in quantum photonic technology.

Findings

High-fidelity logical truth table demonstration

Ability to generate and analyze entangled states

Complete quantum process tomography of the device

Abstract

Integrated photonic circuits have a strong potential to perform quantum information processing. Indeed, the ability to manipulate quantum states of light by integrated devices may open new perspectives both for fundamental tests of quantum mechanics and for novel technological applications. However, the technology for handling polarization encoded qubits, the most commonly adopted approach, is still missing in quantum optical circuits. Here we demonstrate the first integrated photonic Controlled-NOT (CNOT) gate for polarization encoded qubits. This result has been enabled by the integration, based on femtosecond laser waveguide writing, of partially polarizing beam splitters on a glass chip. We characterize the logical truth table of the quantum gate demonstrating its high fidelity to the expected one. In addition, we show the ability of this gate to transform separable states into entangled ones and vice versa. Finally, the full accessibility of our device is exploited to carry out a complete characterization of the CNOT gate through a quantum process tomography.