Programmable entangled qubit states on a linear-optical platform

TL;DR

This paper introduces an advanced linear-optical platform capable of generating high-fidelity entangled qubit states, crucial for scalable photonic quantum computing, through a combination of high-quality photon sources, a programmable chip, and efficient detection.

Contribution

The work demonstrates a fully characterized, programmable photonic chip for high-fidelity entangled state generation, incorporating calibration and error modeling for improved quantum state preparation.

Findings

Achieved 98.5% fidelity in Bell state preparation.

Developed a numerical model accounting for fabrication imperfections.

Demonstrated heralded arbitrary two-qubit state generation.

Abstract

We present an experimental platform for linear-optical quantum information processing. Our setup utilizes multiphoton generation using a high-quality single-photon source, which is demultiplexed across multiple spatial channels, a custom-designed, programmable, low-loss photonic chip, and paired with high-efficiency single-photon detectors. We demonstrate the platform's capability in producing heralded arbitrary two-qubit dual-rail encoded states, a crucial building block for large-scale photonic quantum computers. The programmable chip was fully characterized through a calibration process that allowed us to create a numerical model accounting for fabrication imperfections and measurement errors. As a result, using on-chip quantum state tomography (QST), we achieved high-fidelity quantum state preparation, with a fidelity of 98.5\% specifically for the Bell state.