Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)

Order-Invariant Two-Photon Quantum Correlations in PT-Symmetric Interferometers

Tom A. W. Wolterink, Matthias Heinrich, Stefan Scheel, Alexander Szameit

Published Jun 26, 2023• 0 citations
Publisher

Abstract

Quantum correlations in linear optical networks are a crucial resource for quantum information processing. Correlations between multiple photons are described by the permanent of the transmission matrix of the optical network [1]. Yet, despite their central role, very few properties of permanents are known to exist and the calculation of matrix permanents remains a computationally hard problem, which, at large scale, has sparked the field of boson sampling. However, the lack of tangible properties also affects small-scale networks, as it hinders intuitive prediction of the behavior of composite systems from their components. This especially holds for non-Hermitian systems that incorporate losses, which are known to drastically alter quantum correlations even in networks of just two modes, such as a lossy beam splitter [2], [3]. Here, we systematically identify sequences of two-mode systems that perform distinct transformations, whereas their permanents remain invariant under reversal of the entire sequence's order. We experimentally verify this property by probing the two-photon correlations in parity-time (PT)-symmetric interferometers of wildly different composition.

DOI
10.1109/cleo/europe-eqec57999.2023.10232069

Related papers

Order-Invariant Two-Photon Quantum Correlations in PT-Symmetric Interferometers

Tom A. W. Wolterink, Matthias Heinrich, Stefan Scheel +1 more

Multiphoton correlations in linear photonic quantum networks are governed by matrix permanents. Yet, surprisingly few systematic properties of these crucial algebraic objects are known. As such, predicting the overall multiphoton behavior of a network from its individual building blocks typically defies intuition. In this work, we identify sequences of concatenated two-mode linear optical transformations whose two-photon behavior is invariant under reversal of the order. We experimentally verify this systematic behavior in parity-time-symmetric complex interferometer arrangements of varying compositions. Our results underline new ways in which quantum correlations may be preserved in counterintuitive ways, even in small-scale non-Hermitian networks.

arXiv:2302.11884•ACS Photonics•Sep 12, 2023•3 citations

Order-Invariant Two-Photon Quantum Correlations in PT-Symmetric Interferometers

Tom A. W. Wolterink, Matthias Heinrich, Stefan Scheel +1 more

We identify sequences of concatenated two-mode linear optical transformations whose two-photon behavior is invariant under reversal of the order. We experimentally verify this systematic behavior in parity-time-symmetric complex interferometer arrangements of varying composition.

•Jan 1, 2023•0 citations

Order-Invariant Quantum Correlations in non-Hermitian Interferometers

Tom A. W. Wolterink, Matthias Heinrich, Stefan Scheel +1 more

We identify sequences of concatenated two-mode systems that perform distinct linear optical transformations, whereas their two-photon behavior is invariant under reversal of the order. We experimentally verify this behavior in non-Hermitian interferometers of varying composition.

Quantum 2.0 Conference and Exhibition•Jan 1, 2024•0 citations

Scanning Quantum Interference Across the Unbroken PT-Symmetric Phase

Friederike Klauck, Tom A. W. Wolterink, Matthias Heinrich +1 more

With their conceptual description of Parity-Time symmetry in 1998 [1], Bender and Boettcher inaugurated a new field of studies with fascinating implications on topology [2] and exceptional point dynamics [3], to name a few. Typically, PT-symmetric Hamiltonians exhibit real eigenvalues below a certain threshold, whereas above, the PT-symmetry is spontaneously broken as the eigenvalue spectrum becomes complex. Entirely passive configurations based solely on differential losses [7] allow the physics of PT symmetry to be carried over to a quantum-optical context [6] and explored therein [4]. Here we study the ways in which the degree of loss systematically impacts the characteristics of quantum correlations between interfering photons by analyzing the two-photon correlations in PT-symmetric directional couplers.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 26, 2023•0 citations

Correlation functions and matrix permanents

Vincenzo Tamma, Florian Nägele

The connection between the boson sampling problem in a linear optical interferometer with single photon sources and the computation of matrix permanents has recently brought a strong interest for quantum computing applications. In this work we explore the physics of N-order interference in terms of N-order correlation functions in a generic linear optical interferometer with both Fock states sources and thermal sources. We will show how also in this case the connection of such a problem with matrix permanents play a fundamental role.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Sep 26, 2013•3 citations

Observing PT-Symmetry Breaking in Integrated Quantum Photonics

Friederike Klauck, Matthias Heinrich, Alexander Szameit +1 more

In PT-symmetric systems, losses dramatically alter quantum correlations of interfering photons. We study the impact of increased loss on two-photon correlations in lossy couplers and observe changes in Hong-Ou-Mandel interference upon entering the PT-broken phase.

Quantum 2.0 Conference and Exhibition•Jan 1, 2024•0 citations
Quantum correlations in linear optical networks are a crucial resource for quantum information processing. Correlations between multiple photons are described by the permanent of the transmission matrix of the optical network [1]. Yet, despite their central role, very few properties of permanents are known to exist and the calculation of matrix permanents remains a computationally hard problem, which, at large scale, has sparked the field of boson sampling. However, the lack of tangible properties also affects small-scale networks, as it hinders intuitive prediction of the behavior of composite systems from their components. This especially holds for non-Hermitian systems that incorporate losses, which are known to drastically alter quantum correlations even in networks of just two modes, such as a lossy beam splitter [2], [3]. Here, we systematically identify sequences of two-mode systems that perform distinct transformations, whereas their permanents remain invariant under reversal of the entire sequence's order. We experimentally verify this property by probing the two-photon correlations in parity-time (PT)-symmetric interferometers of wildly different composition.
Multiphoton correlations in linear photonic quantum networks are governed by matrix permanents. Yet, surprisingly few systematic properties of these crucial algebraic objects are known. As such, predicting the overall multiphoton behavior of a network from its individual building blocks typically defies intuition. In this work, we identify sequences of concatenated two-mode linear optical transformations whose two-photon behavior is invariant under reversal of the order. We experimentally verify this systematic behavior in parity-time-symmetric complex interferometer arrangements of varying compositions. Our results underline new ways in which quantum correlations may be preserved in counterintuitive ways, even in small-scale non-Hermitian networks.
With their conceptual description of Parity-Time symmetry in 1998 [1], Bender and Boettcher inaugurated a new field of studies with fascinating implications on topology [2] and exceptional point dynamics [3], to name a few. Typically, PT-symmetric Hamiltonians exhibit real eigenvalues below a certain threshold, whereas above, the PT-symmetry is spontaneously broken as the eigenvalue spectrum becomes complex. Entirely passive configurations based solely on differential losses [7] allow the physics of PT symmetry to be carried over to a quantum-optical context [6] and explored therein [4]. Here we study the ways in which the degree of loss systematically impacts the characteristics of quantum correlations between interfering photons by analyzing the two-photon correlations in PT-symmetric directional couplers.
The connection between the boson sampling problem in a linear optical interferometer with single photon sources and the computation of matrix permanents has recently brought a strong interest for quantum computing applications. In this work we explore the physics of N-order interference in terms of N-order correlation functions in a generic linear optical interferometer with both Fock states sources and thermal sources. We will show how also in this case the connection of such a problem with matrix permanents play a fundamental role.