Two Polarization Entangled Sources from the Same Semiconductor Chip

TL;DR

This paper demonstrates a monolithic semiconductor chip capable of generating multiple types of polarization entangled photon pairs directly on-chip, advancing integrated quantum photonics for practical quantum information applications.

Contribution

It introduces a single chip that produces different polarization entangled states using multiple SPDC processes without off-chip components, enabling fully integrated quantum photon sources.

Findings

Successfully generated polarization entangled photons via type-0, type-I, and type-II SPDC processes.

Achieved on-chip generation of Bell states without external compensation or filtering.

Potential for integration with on-chip pump lasers for fully self-contained quantum sources.

Abstract

Generating nonclassical states of photons such as polarization entangled states on a monolithic chip is a crucial step towards practical applications of optical quantum information processing such as quantum computing and quantum key distribution. Here we demonstrate two polarization entangled photon sources in a single monolithic semiconductor waveguide. The first source is achieved through the concurrent utilization of two spontaneous parametric down-conversion (SPDC) processes, namely type-0 and type-I SPDC processes. The chip can also generate polarization entangled photons via the type-II SPDC process, enabling the generation of both co-polarized and cross-polarized entangled photons in the same device. In both cases, polarization entanglement is generated directly on the chip without the use of any off-chip compensation, interferometry or bandpass filtering. This enables direct, chip-based generation of both Bell states $(|H,H\rangle+|V,V\rangle)/\sqrt{2}$ and $(|H,V\rangle+|V,H\rangle)/\sqrt{2}$ simultaneously utilizing the same pump source. In addition, based on compound semiconductors, this chip can be directly integrated with it own pump laser. This technique ushers an era of self-contained, integrated, electrically pumped, room-temperature polarization entangled photon sources.