New Photonics Platform Demonstrates High-Dimensional Quantum States

Researchers in Italy and France have developed a photonics platform that generates complex quantum states, allowing for more information to be encoded into a single photon. The platform combines a single-photon source based on quantum dots with devices that couple the photons’ polarization and orbital angular momentum (OAM). This results in a deterministic source of bright single photons that can be entangled in the hybrid space of polarization and OAM.

Single photons are commonly used as qubits, but by utilizing OAM, more information can be encoded into photons. Photons in high-dimensional quantum states have the potential for enhanced security protocols in communication networks and more powerful quantum computers. However, creating a deterministic source of single photons with OAM has been challenging.

The new platform solves this problem by using a single-photon source based on semiconductor quantum dots, which can produce indistinguishable single photons in a nearly deterministic manner. The photons’ OAM is adjusted using a device called a q-plate, allowing for the combination of polarization and OAM. This results in quantum states known as vector vortices, which support entanglement between the multiple quantum states within the particle.

The researchers were able to generate pure single photons that are entangled in the hybrid OAM-polarization space without the need for a slow heralding process. They also implemented a two-photon quantum gate, creating pairs of entangled photons within the hybrid space.

This new platform represents a significant advancement in high-dimensional multiphoton experiments and has potential applications in quantum photonic technologies. The research was conducted by the Quantum Information Lab at the Sapienza University of Rome, Italy.

Source: Adv. Photon., doi: 10.1117/1.AP.5.4.046008