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High-dimensional quantum states using QDs and OAM

High-dimensional quantum states using QDs and OAM

Technology News |
By Jean-Pierre Joosting



A team of researchers from Sapienza University of Rome, Paris-Saclay University, and University of Naples Federico II have combined the features of orbital angular momentum (OAM) with those of quantum dots (QDs) to create a bridge between two cutting-edge technologies.

High-dimensional quantum states are the basic ingredients of quantum information science and technology. To manipulate these states, scientists have turned to light, specifically a property called orbital angular momentum (OAM), which deals with how light twists and turns in space. However, making super bright single photons with OAM in a deterministic fashion has been a tough nut to crack.

This bridge built by the researchers can be flexibly used for two goals. First, it can make pure single photons that are entangled within the OAM-polarization space, and the researchers can count them directly. Second, this bridge can also make pairs of photons that are strongly correlated in the quantum world. They’re entangled, so that each single photon state cannot be described independently of the other, even when they’re far apart. This is of paramount importance for quantum communication and encryption.

This new platform has the potential to create hybrid entanglement states both within and between particles, all belonging to high-dimensional Hilbert spaces. On one hand, the team has achieved the generation of pure single photons, whose quantum states exhibit nonseparability within the hybrid OAM-polarization domain. By exploiting an almost deterministic quantum source in combination with a q-plate — a device capable of adjusting the OAM value based on single photon polarization — the researchers can directly validate these states through single-photon counts, thereby avoiding the need for a heralding process and enhancing the rate of generation.

On the other hand, the team also employs the concept of indistinguishability within single photons as a resource to generate pairs of single photons that possess entanglement within the hybrid OAM-polarization space. According to Professor Fabio Sciarrino, head of Quantum Information Lab in the Department of Physics of Sapienza University of Rome, “The proposed flexible scheme represents a step forward in high-dimensional multiphoton experiments, and it could provide an important platform for both fundamental investigations and quantum photonic applications.”

The research by Suprano et al, titled, “Orbital angular momentum based intra- and interparticle entangled states generated via a quantum dot source” can be found at DOI: https://dx.doi.org/10.1117/1.AP.5.4.046008.

Image: Scheme of the flexible platform implemented to engineer both intra- and interparticle Orbital Angular Momentum based entangled states via quantum dot source. Credit Nicolò Spagnolo.

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