We investigate the emergence of long-lived correlations in finite open quantum systems subject to collective dissipation. By analyzing the spectral properties of the Liouvillian superoperator for systems of up to N = 6 qubits, we observe exponential suppression of the spectral gap with system size: ∆(N) ∝ e−αN with α = 1.63 ± 0.05 and coefficient of determination R2 = 0.95. This behavior implies an exponential growth of relaxation times τ = 1/∆ and signals the onset of a dissipative phase transition in the thermodynamic limit. Complementary evidence is provided by data collapse under λ/N scaling, demonstrating collective superradiant behavior, and by the saturation of conditional mutual information, indicating the persistence of nonlocal correlations. Together, these results support a mechanism of symmetry-protected information confinement in driven-dissipative quantum systems
We investigate the emergence of long-lived correlations in finite open quantum systems subject to collective dissipation. By analyzing the spectral properties of the Liouvillian superoperator for systems of up to N = 6 qubits, we observe exponential suppression of the spectral gap with system size: ∆(N) ∝ e−αN with α = 1.63 ± 0.05 and coefficient of determination R2 = 0.95. This behavior implies an exponential growth of relaxation times τ = 1/∆ and signals the onset of a dissipative phase transition in the thermodynamic limit. Complementary evidence is provided by data collapse under λ/N scaling, demonstrating collective superradiant behavior, and by the saturation of conditional mutual information, indicating the persistence of nonlocal correlations. Together, these results support a mechanism of symmetry-protected information confinement in driven-dissipative quantum systems
Collapse as a Dissipative Phase Transition: Liouvillian Gap Opening, Pointer Stability, and τ-Flow Dynamics
Abstract We present a rigorous operator-theoretic formulation of quantum collapse as a dissipative phase transition in the spectrum of a completely positive dynamical semigroup. Within a finite-dimensional Hilbert space, we define collapse in terms of exponential contraction toward a pointer algebra induced by a Liouvillian spectral gap in the coherence sector. We prove that coherence decays at a rate determined by the minimal nonzero real part of the Liouvillian spectrum and establish a sharp stability inequality quantifying competition between dissipative gap opening and Hamiltonian coherence regeneration. We further show that in macroscopic amplification regimes, the gap scales superlinearly in redundancy, producing thermodynamic sharpening analogous to conventional phase transitions. Finally, we demonstrate that this structure emerges naturally from a $ \tau $-recursive dynamical generator of the form $ \mathcal{A} = -iH - \Gamma $, where $ \Gamma $ is constructed from commutator tension $ [H,M]^\dagger[H,M] $. Conclusion: Collapse thus appears not as a primitive stochastic postulate, nor as purely epistemic update, but as a dynamical transition in the spectral structure of the evolution generator. Key Highlights & Physical Implications Novel Resolution to the Measurement Problem: Replaces axiomatic stochastic jumps with a deterministic, spectral phase transition. Commutator Tension Mechanism: Identifies $ [H,M]^\dagger[H,M] $ as the dynamical origin of quantum friction and decoherence. Macroscopic Scaling Laws: Proves superlinear gap growth in redundant apparatuses, explaining why large systems behave classically. Pointer Algebra Stability: Establishes a strict inequality ($ \Delta > \kappa $) that dictates when a system crosses from the coherent phase to the classical pointer phase. Keywords & Index Terms Quantum Measurement Problem, Decoherence Theory, Dissipative Phase Transitions, Open Quantum Systems, Liouvillian Spectral Gap, Pointer States, Lindblad Master Equation, Onto-Physical Entanglement, CPT-Coherence Theory, Commutator Tension, Quantum Trajectories, Thermodynamic Limit.
A state of an open quantum system is described by a density matrix, whose dynamics is governed by a Liouvillian superoperator. Within a general framework, we explore fundamental properties of both first-order dissipative phase transitions and second-order dissipative phase transitions associated with a symmetry breaking. In the critical region, we determine the general form of the steady-state density matrix and of the Liouvillian eigenmatrix whose eigenvalue defines the Liouvillian spectral gap. We illustrate our exact results by studying some paradigmatic quantum optical models exhibiting critical behavior.
In the thermodynamic limit, the steady states of open quantum many-body systems can undergo nonequilibrium phase transitions due to a competition between coherent and driven-dissipative dynamics. Here, we consider Markovian systems and elucidate structures of the Liouville superoperator that generates the time evolution. In many cases of interest, an operator-basis transformation can bring the Liouvillian into a block-triangular form, making it possible to assess its spectrum. The spectral gap sets the asymptotic decay rate. The superoperator structure can be used to bound gaps from below, showing that, in a large class of systems, dissipative phase transitions are actually impossible and that the convergence to steady states follows an exponential temporal decay. Furthermore, when the blocks on the diagonal are Hermitian, the Liouvillian spectra obey Weyl ordering relations. The results apply, for example, to Davies generators and quadratic systems and are also demonstrated for various spin models.
We provide an analysis of the correlation properties of spin and fermionic systems on a lattice evolving according to open system dynamics generated by a local primitive Liouvillian. We show that if the Liouvillian has a spectral gap which is independent of the system size, then the correlations between local observables decay exponentially as a function of the distance between their supports. We prove, furthermore, that if the Log-Sobolev constant is independent of the system size, then the system satisfies clustering of correlations in the mutual information—a much more stringent form of correlation decay. As a consequence, in the latter case we get an area law (with logarithmic corrections) for the mutual information. As a further corollary, we obtain a stability theorem for local distant perturbations. We also demonstrate that gapped free-fermionic systems exhibit clustering of correlations in the covariance and in the mutual information. We conclude with a discussion of the implications of these results for the classical simulation of open quantum systems with matrix-product operators and the robust dissipative preparation of topologically ordered states of lattice spin systems.
We provide an analysis of the correlation properties of spin and fermionic systems on a lattice evolving according to open system dynamics generated by a local primitive Liouvillian. We show that if the Liouvillian has a spectral gap which is independent of the system size, then the correlations between local observables decay exponentially as a function of the distance between their supports. We prove, furthermore, that if the Log-Sobolev constant is independent of the system size, then the system satisfies clustering of correlations in the mutual information ‒ a much more stringent form of correlation decay. As a consequence, in the latter case we get an area law (with logarithmic corrections) for the mutual information. As a further corollary, we obtain a stability theorem for local distant perturbations. We also demonstrate that gapped free-fermionic systems exhibit clustering of correlations in the covariance and in the mutual information. We conclude with a discussion of the implications of these results for the classical simulation of open quantum systems with matrix-product operators and the robust dissipative preparation of topologically ordered states of lattice spin systems.
We theoretically investigate the critical properties of a single driven-dissipative nonlinear photon mode. In a well-defined thermodynamical limit of large excitation numbers, the exact quantum solution describes a first-order phase transition in the regime where semiclassical theory predicts optical bistability. We study the behavior of the complex spectral gap associated with the Liouvillian superoperator of the corresponding master equation. We show that in this limit the Liouvillian gap vanishes exponentially and that the bimodality of the photon Wigner function disappears. The connection between the considered thermodynamical limit of large photon numbers for the single-mode cavity and the thermodynamical limit of many cavities for a driven-dissipative Bose-Hubbard system is discussed.