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

arXiv:2407.03591 · ACS Photonics

Studying Quasi-Parametric Amplifications: From Multiple PT-Symmetric Phase Transitions to Non-Hermitian Sensing

Xiaoxiong Wu, Kai Bai, Penghong Yu, Zhaohui Dong, Yanyan He, Jingui Ma, Vladislav V. Yakovlev, Meng Xiao, Xianfeng Chen, Luqi Yuan

Published Oct 9, 2024• 2 citations
arXivHTMLPDF

Abstract

Quasi-parametric amplification (QPA) is a nonlinear interaction in which the idler wave is depleted through a loss mechanism. QPA plays an important role in signal amplification in ultrafast photonics and quantum light generation. In this report, we explore the generalized features characterized by non-Hermitian parity-time ( PT ) symmetry in the QPA process and uncover multiple PT -symmetric phase transitions in such a QPA process in which transitions are ultrasensitive to external parameters. In particular, we demonstrate the feasibility of detection of 10 –11 inhomogeneities of the doped absorber, which is several orders of magnitude more sensitive than similar measurements performed in a linear absorption regime. In doing so, we reveal a family of PT -symmetric phase transitions appearing in the QPA process and provide a distinctive nonlinear optical sensing mechanism for precise optical measurements.

DOI
10.1021/acsphotonics.4c01071

Related papers

Quantum squeezing and sensing in quadrature parity-time symmetry

Jianming Wen, Wencong Wang, Yanhua Zhai +3 more

Quantum Langevin noise makes the observation of quantum-optical parity-time (PT) symmetry in an open system with both gain and loss elusive. Here, we challenge this problem by exploiting twin beams produced from a nonlinear parametric process, one undergoing phase-sensitive linear quantum amplification (PSA) and the other engaging balanced loss merely. Unlike previous studies involving phase-insensitive linear quantum amplification (PIA), our PSA-loss scheme enables only one pair of quadratures to evolve PT-symmetrically with variances transiting from periodic oscillations to exponential growths when crossing an exceptional point (EP), while tailors the conjugate pair with PT-adjusted quadrature squeezing. We further investigate such asymmetric PT-quadrature squeezing for quantum sensing by evaluating the quantum Cramer–Rao bound with distinct features beyond existing protocols. The proposed quadrature PT sheds new light on continuous-variable based quantum information and technology.

Optical and Quantum Sensing and Precision Metrology II•Mar 8, 2023•0 citations

Anti-Parity-Time Symmetric Optical Four-Wave Mixing in Cold Atoms

Yue Jiang, Yefeng Mei, Ying Zuo +4 more

Non-Hermitian optical systems with parity-time (PT) symmetry have recently revealed many intriguing prospects that outperform conservative structures. The previous works are mostly rooted in complex arrangements with controlled gain-loss interplay. Here, we demonstrate anti-PT symmetry inherent in the nonlinear optical interaction based upon forward optical four-wave mixing in a laser-cooled atomic ensemble with negligible linear gain and loss. We observe that the pair of frequency modes undergo a nontrivial anti-PT phase transition between coherent power oscillation and optical parametric amplification in presence of a large phase mismatch.

arXiv:1901.06805•Physical Review Letters•Nov 8, 2019•123 citations

Aspects of Parity-time Symmetry Breaking in Discrete, Classical and Quantum Open Systems

Andrew K. Harter

Analysis of fundamentally open systems which exhibit both spatial reflection (parity) and time-reversal symmetry, called PT-symmetric [1] systems, has played an important role in understanding the dynamics of a broad class of non-Hermitian systems. Such systems support distinct regimes of stability and instability respectively, and the transition between these plays an important role in the system dynamics. We investigate a variety of non-Hermitian systems which exhibit a PT-symmetry breaking transition in both classical and quantum contexts using an array of theoretical and numerical approaches which are directly amenable to physical experiments. Organizationally, we divide these studies into those done on classical and quantum systems. Specifically for classical systems we analyze several interesting phenomena in the context of optical waveguide arrays. These provide an important testing ground for much of the discrete, PT-symmetric theory. In our case, we analyze PT-symmetric extensions of several interesting lattice models. Firstly, we explore single gain/loss pair, PT-symmetric extensions of the Su-Schreiffer-Heeger (SSH) model [2] and the Aubry-Andre-Harper (AAH) model [3,4]. In both cases, we find a veiled symmetry which is responsible for the PT-symmetry. Secondly we expand upon the Rudner-Levitov (RL) model [5,6], a non-Hermitian extension of the SSH model with multiple gain/loss pairs, and we explore the dependence of topological phenomena on changes in the initial state as well as their robustness in the presence of gain-induced nonlinearity. For quantum systems, we explore the rich PT-symmetric phase diagram resulting from time-periodic, Floquet PT-symmetry [7,8]. This is experimentally implementable in ultracold atomic systems [9], and features a reentrant PT-symmetric phase. Secondly, we examine quantum multi-photon statistics for a simple non-Hermitian model which is transformed and mapped to a system with unitary evolution via a unitary dilation, and is fully realizable on a small-scale quantum simulator [10].

•Jan 1, 2018•0 citations

Quadrature-PT symmetry: classical-to-quantum transition in noise fluctuations

Wencong Wang, Yanhua Zhai, Dongmei Liu +3 more

Abstract While gain-loss-coupled photonic platforms have achieved significant success in studying classical parity-time (PT) symmetry, they encounter challenges in demonstrating pure quantum effects due to incompatible operator transformations and Langevin noise. Here, we present compelling evidence that a non-Hermitian (NH) twin-beam system, undergoing phase-sensitive amplification and balanced loss, not only enables observing the usual eigenvalue-associated PT phase transition but also exhibits distinctive features absent in classical NH or traditional Hermitian quantum scenarios, encompassing quadrature PT symmetry, anomalous loss-induced quadrature squeezing, and classical-to-quantum (C2Q) transitions in noise fluctuations. Furthermore, our proposed bipartite open system promises optimal sensing for various quantum observable measurements, showcasing an improved signal-to-noise ratio and sensitivity, constrained by quantum Cramér–Rao bound or Fisher information. These findings deepen the comprehension of authentic quantum optical PT symmetry involving both gain and loss, addressing contentious issues and illuminating new facets of the subject.

arXiv:2301.05511•Quantum Science and Technology•Jan 24, 2025•7 citations

Non-Hermitian nonlinear optics without gain and loss

Yue Jiang, Yefeng Mei, Ying Zuo +3 more

Non-Hermitian optical systems with parity-time (PT) symmetry have recently revealed many intriguing prospects that outperform conservative structures. The prevous works are mostly rooted in complex arrangements with controlled gain-loss interplay. Here, we demonstrate anti-PT symmetry inherent in nonlinear optical interactions based upon forward optical four-wave mixing in a laser-cooled atomic ensemble with negligible linear gain and loss. We observe the pair of frequency modes undergo a nontrivial anti-PT phase transition between coherent power oscillation and optical parametric amplification in presence of a large phase mismatch.

•Jan 21, 2019•0 citations

Nonlinear quantum spectroscopy with parity–time-symmetric integrated circuits

Pawan Kumar, Sina Saravi, Thomas Pertsch +2 more

We propose a novel quantum nonlinear interferometer design that incorporates a passive parity–time (PT)-symmetric coupler sandwiched between two nonlinear sections where signal–idler photon pairs are generated. The PT symmetry enables efficient coupling of the longer-wavelength idler photons and facilitates the sensing of losses in the second waveguide exposed to analyte under investigation, whose absorption can be inferred by measuring only the signal intensity at a shorter wavelength where efficient detectors are readily available. Remarkably, we identify a new phenomenon of sharp signal intensity fringe shift at critical idler loss values, which is distinct from the previously studied PT symmetry breaking. We discuss how such unconventional properties arising from quantum interference can provide a route to enhancing the sensing of analytes and facilitate broadband spectroscopy applications in integrated photonic platforms.

arXiv:2203.08703•Photonics Research•Apr 26, 2022•4 citations
Quasi-parametric amplification (QPA) is a nonlinear interaction in which the idler wave is depleted through a loss mechanism. QPA plays an important role in signal amplification in ultrafast photonics and quantum light generation. In this report, we explore the generalized features characterized by non-Hermitian parity-time ( PT ) symmetry in the QPA process and uncover multiple PT -symmetric phase transitions in such a QPA process in which transitions are ultrasensitive to external parameters. In particular, we demonstrate the feasibility of detection of 10 –11 inhomogeneities of the doped absorber, which is several orders of magnitude more sensitive than similar measurements performed in a linear absorption regime. In doing so, we reveal a family of PT -symmetric phase transitions appearing in the QPA process and provide a distinctive nonlinear optical sensing mechanism for precise optical measurements.
Quantum Langevin noise makes the observation of quantum-optical parity-time (PT) symmetry in an open system with both gain and loss elusive. Here, we challenge this problem by exploiting twin beams produced from a nonlinear parametric process, one undergoing phase-sensitive linear quantum amplification (PSA) and the other engaging balanced loss merely. Unlike previous studies involving phase-insensitive linear quantum amplification (PIA), our PSA-loss scheme enables only one pair of quadratures to evolve PT-symmetrically with variances transiting from periodic oscillations to exponential growths when crossing an exceptional point (EP), while tailors the conjugate pair with PT-adjusted quadrature squeezing. We further investigate such asymmetric PT-quadrature squeezing for quantum sensing by evaluating the quantum Cramer–Rao bound with distinct features beyond existing protocols. The proposed quadrature PT sheds new light on continuous-variable based quantum information and technology.
Non-Hermitian optical systems with parity-time (PT) symmetry have recently revealed many intriguing prospects that outperform conservative structures. The previous works are mostly rooted in complex arrangements with controlled gain-loss interplay. Here, we demonstrate anti-PT symmetry inherent in the nonlinear optical interaction based upon forward optical four-wave mixing in a laser-cooled atomic ensemble with negligible linear gain and loss. We observe that the pair of frequency modes undergo a nontrivial anti-PT phase transition between coherent power oscillation and optical parametric amplification in presence of a large phase mismatch.
Analysis of fundamentally open systems which exhibit both spatial reflection (parity) and time-reversal symmetry, called PT-symmetric [1] systems, has played an important role in understanding the dynamics of a broad class of non-Hermitian systems. Such systems support distinct regimes of stability and instability respectively, and the transition between these plays an important role in the system dynamics. We investigate a variety of non-Hermitian systems which exhibit a PT-symmetry breaking transition in both classical and quantum contexts using an array of theoretical and numerical approaches which are directly amenable to physical experiments. Organizationally, we divide these studies into those done on classical and quantum systems. Specifically for classical systems we analyze several interesting phenomena in the context of optical waveguide arrays. These provide an important testing ground for much of the discrete, PT-symmetric theory. In our case, we analyze PT-symmetric extensions of several interesting lattice models. Firstly, we explore single gain/loss pair, PT-symmetric extensions of the Su-Schreiffer-Heeger (SSH) model [2] and the Aubry-Andre-Harper (AAH) model [3,4]. In both cases, we find a veiled symmetry which is responsible for the PT-symmetry. Secondly we expand upon the Rudner-Levitov (RL) model [5,6], a non-Hermitian extension of the SSH model with multiple gain/loss pairs, and we explore the dependence of topological phenomena on changes in the initial state as well as their robustness in the presence of gain-induced nonlinearity. For quantum systems, we explore the rich PT-symmetric phase diagram resulting from time-periodic, Floquet PT-symmetry [7,8]. This is experimentally implementable in ultracold atomic systems [9], and features a reentrant PT-symmetric phase. Secondly, we examine quantum multi-photon statistics for a simple non-Hermitian model which is transformed and mapped to a system with unitary evolution via a unitary dilation, and is fully realizable on a small-scale quantum simulator [10].
Abstract While gain-loss-coupled photonic platforms have achieved significant success in studying classical parity-time (PT) symmetry, they encounter challenges in demonstrating pure quantum effects due to incompatible operator transformations and Langevin noise. Here, we present compelling evidence that a non-Hermitian (NH) twin-beam system, undergoing phase-sensitive amplification and balanced loss, not only enables observing the usual eigenvalue-associated PT phase transition but also exhibits distinctive features absent in classical NH or traditional Hermitian quantum scenarios, encompassing quadrature PT symmetry, anomalous loss-induced quadrature squeezing, and classical-to-quantum (C2Q) transitions in noise fluctuations. Furthermore, our proposed bipartite open system promises optimal sensing for various quantum observable measurements, showcasing an improved signal-to-noise ratio and sensitivity, constrained by quantum Cramér–Rao bound or Fisher information. These findings deepen the comprehension of authentic quantum optical PT symmetry involving both gain and loss, addressing contentious issues and illuminating new facets of the subject.
Non-Hermitian optical systems with parity-time (PT) symmetry have recently revealed many intriguing prospects that outperform conservative structures. The prevous works are mostly rooted in complex arrangements with controlled gain-loss interplay. Here, we demonstrate anti-PT symmetry inherent in nonlinear optical interactions based upon forward optical four-wave mixing in a laser-cooled atomic ensemble with negligible linear gain and loss. We observe the pair of frequency modes undergo a nontrivial anti-PT phase transition between coherent power oscillation and optical parametric amplification in presence of a large phase mismatch.
We propose a novel quantum nonlinear interferometer design that incorporates a passive parity–time (PT)-symmetric coupler sandwiched between two nonlinear sections where signal–idler photon pairs are generated. The PT symmetry enables efficient coupling of the longer-wavelength idler photons and facilitates the sensing of losses in the second waveguide exposed to analyte under investigation, whose absorption can be inferred by measuring only the signal intensity at a shorter wavelength where efficient detectors are readily available. Remarkably, we identify a new phenomenon of sharp signal intensity fringe shift at critical idler loss values, which is distinct from the previously studied PT symmetry breaking. We discuss how such unconventional properties arising from quantum interference can provide a route to enhancing the sensing of analytes and facilitate broadband spectroscopy applications in integrated photonic platforms.