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

Jiang, Yue; Mei, Yefeng; Zuo, Ying; Zhai, Yao; Li, Jensen; Wen, Jianming; Du, Shengwang

doi:10.1103/physrevlett.123.193604

Cited by 99 publications

(74 citation statements)

References 44 publications

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“…On the other hand, the anti-PT -symmetric Hamiltonian of growing interest satisfies {H,PT } = 0 and can possess purely imaginary eigenvalues. Recently, anti-PT symmetry has been widely observed in atomic systems [14,15], electrical circuits [16], diffusive thermal materials [17], a magnon-cavity-magnon coupled system [18], coupled waveguide systems [19,20], and a single microcavity with nonlinear Brillouin scattering [21]. Such systems can also display some noteworthy effects, including constant refraction [22], * liuyl@baqis.ac.cn nonreciprocity and enhanced sensing [23], and information flow [24].…”

Section: Introductionmentioning

confidence: 99%

Energy-level attraction and heating-resistant cooling of mechanical resonators with exceptional points

2021

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We study the energy-level evolution and ground-state cooling of mechanical resonators under a synthetic phononic gauge field. The tunable gauge phase is mediated by the phase difference between the PT -and anti-PT -symmetric mechanical couplings in a multimode optomechanical system. The transmission spectrum then exhibits an asymmetric Fano line shape or a double optomechanically induced transparency by modulating the gauge phase. Moreover, the eigenvalues will collapse and become degenerate, although the mechanical coupling is continuously increased. Such counterintuitive energy-level attraction, instead of anticrossing, is attributed to destructive interferences between PT -and anti-PT -symmetric couplings. We find that the energy-level attraction, as well as the accompanying exceptional points (EPs), can be clearly observed in the cavity output power spectrum where the mechanical eigenvalues correspond to distinct peaks. For mechanical cooling, the average phonon occupation number is minimized at the EPs. Especially, phonon transport becomes nonreciprocal and even ideally unidirectional at the EPs. Finally, we propose a heating-resistant ground-state cooling based on the nonreciprocal phonon transport, which is mediated by the gauge field. Towards the quantum regime of macroscopic mechanical resonators, most optomechanical systems are ultimately limited by their intrinsic cavity or mechanical heating. Our work shows that the thermal energy transfer can be blocked by tuning the gauge phase, which suggests a promising route to bypass the heating limitations.

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Section: Introductionmentioning

confidence: 99%

Energy-level attraction and heating-resistant cooling of mechanical resonators with exceptional points

2021

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“…Equation ( 1 ) is valid under the slowly varying envelope approximation and neglects linear losses, which are much smaller than the Brillouin gain in our setup. The Hamiltonian is non-Hermitian and satisfies anti-PT symmetry 9 , 10 , 46 , 47 , since its diagonal and off-diagonal terms obey the relations and , respectively. The imaginary coupling is due to the joint amplification or depletion of the probes through the acoustic modes, depending on their relative phases.…”

Section: Resultsmentioning

confidence: 99%

“…This broken phase arises at the exceptional point (EP) of the system, at which the two eigenvalues and eigenmodes coalesce into one 2 . The eigenvalues around the EP are extremely sensitive to perturbations in the system parameters, hence EP physics has been raising great interest in recent years 3 , both from the fundamental research standpoint and in the context of various signal processing and sensing applications 4 , with demonstrations in a number of physical platforms to date [5][6][7][8][9][10][11][12][13][14][15] . For the most part, optics-based realizations have made use of integrated nanophotonic devices and nanostructures [16][17][18][19][20][21][22] , typically relying on coupled microresonators with careful control over resonance frequencies, gain and loss balance, and coupling strength.…”

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confidence: 99%

Observation of anti-parity-time-symmetry, phase transitions and exceptional points in an optical fibre

et al. 2021

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The exotic physics emerging in non-Hermitian systems with balanced distributions of gain and loss has recently drawn a great deal of attention. These systems exhibit phase transitions and exceptional point singularities in their spectra, at which eigen-values and eigen-modes coalesce and the overall dimensionality is reduced. So far, these principles have been implemented at the expense of precise fabrication and tuning requirements, involving tailored nano-structured devices with controlled optical gain and loss. In this work, anti-parity-time symmetric phase transitions and exceptional point singularities are demonstrated in a single strand of single-mode telecommunication fibre, using a setup consisting of off-the-shelf components. Two propagating signals are amplified and coupled through stimulated Brillouin scattering, enabling exquisite control over the interaction-governing non-Hermitian parameters. Singular response to small-scale variations and topological features arising around the exceptional point are experimentally demonstrated with large precision, enabling robustly enhanced response to changes in Brillouin frequency shift.

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“…Chiral mode switching for symmetry-broken modes was found to be relevant to the implementation of anti-parity-time (APT)-symmetric waveguide systems [31]. An APTsymmetric system, whose Hamiltonian anticommutes with the combined PT operator, represents an extension of PT-symmetric systems [32,33], and it also possesses the EP and self-intersecting eigenvalue topological Riemann surface [33][34][35][36]. Mathematically, an APT-symmetric Hamiltonian differs from a PT-symmetric one by a factor of the imaginary unit [32,34].…”

Section: Introductionmentioning

confidence: 99%

Chiral mode transfer of symmetry-broken states in anti-parity-time-symmetric mechanical system

Geng

Zhang

et al. 2021

Proc. R. Soc. A.

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Non-Hermitian systems with parity-time (PT) symmetry reveal rich physics beyond the Hermitian regime. As the counterpart of conventional PT symmetry, anti-parity-time (APT) symmetry may lead to new insights and applications. Complementary to PT-symmetric systems, non-reciprocal and chiral mode switching for symmetry-broken modes have been reported in optics with an exceptional point dynamically encircled in the parameter space of an APT-symmetric system. However, it has remained an open question whether and how the APT-symmetry-induced chiral mode transfer could be realized in mechanical systems. This paper investigates the implementation of APT symmetry in a three-element mass–spring system. The dynamic encircling of an APT-symmetric exceptional point has been implemented using dynamic-modulation mechanisms with time-driven stiffness. It is found that the dynamic encircling of an exceptional point in an APT-symmetric system with the starting point near the symmetry-broken phase leads to chiral mode switching. These findings may provide new opportunities for unprecedented wave manipulation in mechanical systems.

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

Cited by 99 publications

References 44 publications

Energy-level attraction and heating-resistant cooling of mechanical resonators with exceptional points

Energy-level attraction and heating-resistant cooling of mechanical resonators with exceptional points

Observation of anti-parity-time-symmetry, phase transitions and exceptional points in an optical fibre

Chiral mode transfer of symmetry-broken states in anti-parity-time-symmetric mechanical system

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