Spontaneous symmetry breaking and inversion-line spectroscopy in gas mixtures

Presilla, Carlo; Jona-Lasinio, G.

doi:10.1103/physreva.91.022709

Cited by 8 publications

(20 citation statements)

References 31 publications

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“…This work paves the way to the study of macroscopic quantum tunneling in the hysteretic regime in the context of the quantum-to-classical transition problem26. Furthermore it will be interesting to explore spontaneous symmetry breaking in gas mixtures as a function of the interspecies interactions27,28. Finally our system will allow investigation of the creation of quantum fluctuations29 and entanglement5 at the critical points as a resource for precision measurements30 and other quantum technologies31.…”

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confidence: 94%

Quantum phase transitions with parity-symmetry breaking and hysteresis

et al. 2016

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Symmetry-breaking quantum phase transitions play a key role in several condensed matter, cosmology and nuclear physics theoretical models [1][2][3] . Its observation in real systems is often hampered by finite temperatures and limited control of the system parameters. In this work we report, for the first time, the experimental observation of the full quantum phase diagram across a transition where the spatial parity symmetry is broken. Our system consists of an ultracold gas with tunable attractive interactions trapped in a spatially symmetric double-well potential. At a critical value of the interaction strength, we observe a continuous quantum phase transition where the gas spontaneously localizes in one well or the other, thus breaking the underlying symmetry of the system. Furthermore, we show the robustness of the asymmetric state against controlled energy mismatch between the two wells. This is the result of hysteresis associated with an additional discontinuous quantum phase transition that we fully characterize. Our results pave the way to the study of quantum critical phenomena at finite temperature 4 , the investigation of macroscopic quantum tunnelling of the order parameter in the hysteretic regime and the production of strongly quantum entangled states at critical points .Parity is a fundamental discrete symmetry of nature 6 conserved by gravitational, electromagnetic and strong interactions 7 . It states the invariance of a physical phenomenon under mirror reflection. Our world is pervaded by robust discrete asymmetries, spanning from the imbalance of matter and antimatter to the homo-chirality of DNA of all living organisms 8 . Their origin and stability is a subject of active debate. Quantum mechanics predicts that asymmetric states can be the result of phase transitions occurring at zero temperature, named in the literature as quantum phase transitions (QPTs) 1,4 . The breaking of a discrete symmetry via a QPT provides also asymmetric states that are particularly robust against external perturbations. Indeed, the order parameter of a continuous-symmetry-breaking QPT can freely (with no energy cost) wander along the valley of a 'mexican hat' Ginzburg-Landau potential (GLP) by coupling with gapless Goldstone modes 9 . In contrast, the order parameter of discrete-symmetry-breaking QPTs is governed by a one-dimensional double-well GLP 10 . The reduced dimensionality suppresses Goldstone excitations, and the order parameter can remain trapped at the bottom of one of the two wells. This provides a robust hysteresis associated with a first-order QPT.Evidence of parity-symmetry breaking has been reported in relativistic heavy-ions collisions 11 and in engineered photonic crystal fibres 12 . Observation of parity-symmetry breaking in a QPT has been reported for neutral atoms coupled to a high-finesse optical cavity 13 . However, this is a strongly dissipative system, with no direct access to the symmetry-breaking mechanism necessary to study the robustness of asymmetric states. In addition, previous the...

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confidence: 94%

Quantum phase transitions with parity-symmetry breaking and hysteresis

et al. 2016

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“…The intermolecular interaction is one of the effects of the environment attributing to the stabilization of chiral molecules [8][9][10][11][12]. Many approaches have been proposed to quantitatively deal with the effect of the intermolecular interaction, where the most well-known ones are the mean-field theory [13,17,18] and the decoherence theory [14,15,[19][20][21][22][23]. There are also proposals combining both the mean- * liyong@csrc.ac.cn field and the decoherence theories to study the stabilization of chiral molecules [16,24].…”

Section: Introductionmentioning

confidence: 99%

“…There are also proposals combining both the mean- * liyong@csrc.ac.cn field and the decoherence theories to study the stabilization of chiral molecules [16,24]. According to the mean-field theory, the stabilization of chiral molecules is the result of a quantum phase transition from an achiral phase to a chiral phase [17,18], namely the achiral-chiral transition. According to the decoherence theory, the stabilization of chiral molecules can be understood [14] in analogy to the quantum Zeno effect [25] when the environment behaves as continuously monitoring the molecular state.…”

Section: Introductionmentioning

confidence: 99%

Static nonlinear Schrödinger equations for the achiral-chiral transitions of polar chiral molecules

Zhang

2019

Phys. Rev. A

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In the mean-field theory, the stabilization of polar chiral molecules is understood as a quantum phase transition where the mean-field ground state of molecules changes from the achiral eigenstate of the molecular Hamiltonian to one of the degenerated chiral states as the increase of the intermolecular interaction. Starting from the many-body Hamiltonian of the molecular gases with electric dipole-dipole interactions, we give the static non-linear Schrödinger equations without free parameters to explore the achiral-chiral transitions of polar chiral molecules. We find that the polar chiral molecules of different species can be classified into two categories: At the critical point for the achiral-chiral transition, the mean-field ground state changes continuously in one category, and changes discontinuously in the other category. We further give the mean-field phase diagram of the achiral-chiral transitions for both two categories.

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“…They can be all the same or belonging to different species, distinguishable or indistinguishable, located at fixed positions or moving in a lattice or in a box. Examples range from a pure gas [11] or a mixture [12] of chiral molecules at a low density, to a chipset of superconducting flux qubits [13]. Ensembles of N mutually noninteracting systems are nontrivial when coupled to an environment.…”

Section: Introductionmentioning

confidence: 99%

Thermalization of noninteracting quantum systems coupled to blackbody radiation: A Lindblad-based analysis

Ostilli

Presilla

2017

Phys. Rev. A

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We study the thermalization of an ensemble of N elementary, arbitrarily-complex, quantum systems, mutually noninteracting but coupled as electric or magnetic dipoles to a blackbody radiation. The elementary systems can be all the same or belong to different species, distinguishable or indistinguishable, located at fixed positions or having translational degrees of freedom. Even if the energy spectra of the constituent systems are nondegenerate, as we suppose, the ensemble unavoidably presents degeneracies of the energy levels and/or of the energy gaps. We show that, due to these degeneracies, a thermalization analysis performed by the popular quantum optical master equation reveals a number of serious pathologies, possibly including a lack of ergodicity. On the other hand, a consistent thermalization scenario is obtained by introducing a Lindblad-based approach, in which the Lindblad operators, instead of being derived from a microscopic calculation, are established as the elements of an operatorial basis with squared amplitudes fixed by imposing a detailed balance condition and requiring their correspondence with the dipole transition rates evaluated under the first-order perturbation theory. Due to the above-mentioned degeneracies, this procedure suffers a basis arbitrariness which, however, can be removed by exploiting the fact that the thermalization of an ensemble of noninteracting systems cannot depend on the ensemble size. As a result, we provide a clear-cut partitioning of the thermalization time into dissipation and decoherence times, for which we derive formulas giving the dependence on the energy levels of the elementary systems, the size N of the ensemble, and the temperature of the blackbody radiation.

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Spontaneous symmetry breaking and inversion-line spectroscopy in gas mixtures

Cited by 8 publications

References 31 publications

Quantum phase transitions with parity-symmetry breaking and hysteresis

Quantum phase transitions with parity-symmetry breaking and hysteresis

Static nonlinear Schrödinger equations for the achiral-chiral transitions of polar chiral molecules

Thermalization of noninteracting quantum systems coupled to blackbody radiation: A Lindblad-based analysis

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