Manipulating multi-photon entanglement in waveguide quantum circuits

TL;DR

This paper demonstrates precise control and manipulation of multi-photon entanglement on integrated photonic circuits, enabling advanced quantum metrology and reconfigurable quantum interference for quantum technologies.

Contribution

It introduces integrated on-chip control of multi-photon entanglement and reconfigurable quantum circuits, advancing scalable quantum photonic technologies.

Findings

Achieved 98.2% interference contrast in path-encoded qubits.

Generated 2- and 4-photon entangled states with high interference contrast.

Demonstrated reconfigurable circuits with tunable quantum interference.

Abstract

On-chip integrated photonic circuits are crucial to further progress towards quantum technologies and in the science of quantum optics. Here we report precise control of single photon states and multi-photon entanglement directly on-chip. We manipulate the state of path-encoded qubits using integrated optical phase control based on resistive elements, observing an interference contrast of 98.2+/-0.3%. We demonstrate integrated quantum metrology by observing interference fringes with 2- and 4-photon entangled states generated in a waveguide circuit, with respective interference contrasts of 97.2+/-0.4% and 92+/-4%, sufficient to beat the standard quantum limit. Finally, we demonstrate a reconfigurable circuit that continuously and accurately tunes the degree of quantum interference, yielding a maximum visibility of 98.2+/- 0.9%. These results open up adaptive and fully reconfigurable photonic quantum circuits not just for single photons, but for all quantum states of light.