Quantum correlations in PT-symmetric photonic integrated circuits

Informations projet

QUAPT

N° de convention de subvention: 895254

DOI

10.3030/895254

Projet clôturé

Date de signature de la CE 15 Avril 2020

Date de début 1 Decembre 2020

Date de fin 30 Avril 2023

Financé au titre de

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Coût total

€ 162 806,40

Contribution de l’UE

€ 162 806,40

Coordonné par

UNIVERSITAET ROSTOCK
Germany

Periodic Reporting for period 1 - QUAPT (Quantum correlations in PT-symmetric photonic integrated circuits)

Période du rapport: 2020-12-01 au 2022-11-30

Résumé du contexte et des objectifs généraux du projet

A central principle in quantum mechanics is that all operators that are associated with observables have to be Hermitian, to ensure real eigenvalues. Surprisingly, it turned out that there exists a class of Hamiltonians which are non-Hermitian yet still possess real eigenvalues. These describe PT-symmetric materials, which are systems that are invariant under the combined operations of parity inversion and time reversal. Moreover, through tuning of a physical parameter, it is possible to induce a phase transition in which the PT symmetry breaks at an exceptional point, rendering the eigenvalue spectrum of the system complex. What implications PT symmetry has for quantum physics is still under debate. Yet, mapped onto a photonic platform, various unusual effects onto the evolution of light have already been demonstrated and the concept even found its way to applications in lasers, optical diodes and sensing. While these experiments have been inspired by quantum mechanical concepts, they have been purely classical so far. Quantum evolution of light in PT-symmetric systems is still completely unexplored territory, with lots of new physics to be unravelled. Therefore, the objective of this action was to experimentally investigate the evolution of quantum states in PT-symmetric systems. This was carried out by implementing quantum walks of multiple correlated photons injected in PT-symmetric photonic integrated circuits fabricated using femtosecond-laser direct writing technology.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

The action investigated various aspects of the evolution of quantum states in PT-symmetric photonic systems. Two highlights are:
1) The nature of two-photon correlations in PT-symmetric quantum systems alternates between bunching and antibunching as a function of the evolution length. Furthermore, a symmetry has been identified that preserves the two-photon behaviour in sequences of non-Hermitian two-mode systems. These results have been submitted for publication and have been presented at several conferences.
2) Harnessing concepts from supersymmetry, one-dimensional photonic systems can be transformed into two-dimensional counterparts while preserving key properties of the system.
This facilitates the fabrication of photonic circuits for applications in perfect imaging and coherent transfer of quantum states. These findings have resulted in a publication and have been presented at several conferences.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

The action furthered the state of art by addressing the question what consequences the existence of PT-symmetric systems has for quantum physics, which put it at the forefront of fundamental research. Furthermore, the results demonstrate that non-Hermiticity in fact enables new functionality, which may impact the design of photonic integrated circuits for applications in advanced quantum information processing and sensing.

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