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:2610.30555

Probing quasiperiodic spectral accessibility with a finite-rate quantum Otto cycle

Shujie Cheng, Lucas C. Céleri, Norton G. de Almeida, Gao Xianlong, G. D. de Moraes Neto

quant-phcond-mat.stat-mechSubmitted Oct 22, 2026• Announced Oct 23, 2026• 0 citations
arXivHTMLPDF

Abstract

Quasiperiodic systems combine sharply different spectral and localisation regimes with a dense hierarchy of dynamical time scales. We show that a finite-rate quantum Otto cycle can use this structure as a thermodynamic probe, revealing which parts of the spectrum become dynamically accessible and thermodynamically relevant during a driven transformation. For a generalised Aubry-André-Harper chain, the resulting response is not determined by the static quasiperiodic regime alone: extended, near-critical, and crossing protocols do not exhibit universal ordering of work fluctuations. Instead, the statistics reflect transition pathways that are simultaneously dynamically coupled, thermally occupied, and energetically significant. The same spectral accessibility separates thermodynamic recovery from microscopic adiabatic recovery. Positive mean work can reappear while the population transfer dynamics remain strongly nonadiabatic because finite-rate population transfer is redistributed toward energetically less costly channels rather than suppressed. The full work distribution reveals a further separation, with a finite rate window in which positive-work cycles form a majority although the mean work remains negative. This behaviour persists in finite-size analysis. A thermally weighted spectral susceptibility connects these effects to a distributed hierarchy of dynamically active spectral regions rather than to a single minimum-gap bottleneck. Finite thermal contacts preserve this picture while introducing a second time scale and intercycle memory. Quantum Otto cycles can therefore provide a fluctuation-resolved thermodynamic probe of quasiperiodic spectral accessibility, complementary to direct spectroscopic and eigenstate-resolved diagnostics.

Related papers

Cross-Spectral Reservoir Correlations as a Resource for Finite-Time Quantum Otto Engines

Siddhartha Dutta, Sujay Mondal, Ankush Das +2 more

We investigate the thermodynamic consequences of longitudinal-transverse cross-spectral reservoir correlations in a finite-time quantum Otto engine with a two-level working medium. Each reservoir couples through excitation-relaxation and dephasing channels whose fluctuations are characterized by a Hermitian positive-semidefinite spectral-density matrix, with the off-diagonal elements encoding their cross correlations. The finite-time isochoric dynamics is derived within the second-order time-convolutionless framework, without imposing the Markov limit at the outset, so that finite reservoir-memory effects can enter through time-dependent dissipative and reservoir-induced coherent contributions. The resulting dynamics is then recast in Bloch-vector form to construct the stroke-resolved cycle dynamics. At fixed auto-spectral densities, cross-spectral correlations modify the populations and coherences of the working medium and thereby its thermodynamic performance. Increasing the correlation strength can enhance the output power, with the enhancement controlled by the cross-spectral phase and characteristic frequency scale. The correlations also reshape the transient cycle-to-cycle evolution and the approach to periodic operation, while the limit-cycle efficiency remains fixed at the Otto value for the population-preserving unitary strokes considered here. These results establish off-diagonal reservoir spectra as an additional resource for controlling finite-time quantum thermal machines.

quant-pharXiv:2608.30496•Sep 1, 2026•0 citations

Adiabatic Otto-like quantum thermodynamical cycle in the non-quasi-static regime

Salvador J. Robles-Pérez, Salvador Castillo-Rivera

We show a finite-time Otto-like quantum thermodynamic cycle that preserves the adiabatic population structure of a time-dependent harmonic oscillator in the non-quasi-static regime. In the conventional energy representation, finite-rate driving induces non-adiabatic population redistribution and leaves residual excitations after the Hamiltonian has returned to its initial value. We show that this difficulty can be avoided by formulating the dynamics in the Lewis-Riesenfeld invariant representation, without modifying the physical Hamiltonian through auxiliary counterdiabatic driving. For a parametric Mathieu protocol, quantum inertia produces a mismatch between the spatial width of the working mode and its transient dressed energy scale. We propose an experimental implementation of this scheme in a trapped-ion Paul trap using stimulated Raman interactions, with independent control of the laser detuning and beam intersection angle. This provides a finite-time implementation in which the invariant population structure is preserved while the physical trap frequency evolves non-quasi-statically. Our results establish a clear distinction between adiabatic operation and quasi-static driving, providing a route toward finite-time quantum thermal cycles that retain the adiabatic energy structure without requiring the quasi-static limit.

quant-pharXiv:2608.26690•Aug 28, 2026•0 citations

Probing critical phases in quasiperiodic systems via subsystem information capacity

Huaijin Dong, Long Zhang

We systematically investigate the entanglement and information dynamics of quasiperiodic systems across their extended, critical, and localized phases, aiming to identify dynamical signatures that can reveal the multifractal spatial structure of critical states and distinguish critical phases from the extended and localized regimes. Focusing on the generalized Aubry-André-Harper model, we complement the half-chain entanglement entropy with the spatially resolved subsystem information capacity (SIC) and demonstrate that critical states exhibit pronounced spatial heterogeneity absent in the extended and localized phases. In the steady state, the SIC reveals a stepwise ramp as a function of subsystem size, reflecting an underlying fragmentation of the chain into weakly connected subregions. Dynamically, information initially localized within such a subregion can undergo coherent long-lived oscillations, dubbed subregion echoes, whose period scales with the subregion length, in quantitative agreement with a quasiparticle picture of confined quasiparticle reflections. We trace this internal fragmentation to the incommensurately distributed zeros (IDZs) in the off-diagonal hopping terms of the Hamiltonian. To establish the generality of the SIC as a diagnostic tool, we further apply it to a mobility-edge phase with coexisting extended and localized states and to a critical phase that does not originate from IDZ fragmentation, and show that the SIC can cleanly distinguish these scenarios through their distinct steady-state profiles, initial-site sensitivities, and the presence or absence of subregion echoes. Our results demonstrate that the SIC serves as a powerful real-space probe for diagnosing critical phases and uncovering the bottlenecked connectivity that underlies the multifractal structure of critical states.

cond-mat.dis-nnCross-listedarXiv:2605.06075•Physical review. B./Physical review. B•May 8, 2026•0 citations

Thermodynamic cost of a periodically driven quantum system beyond the adiabatic regime

Xiaoyun Wang, Haowei Wang, Dazhi Xu

Abstract Finite-time periodic control of an open quantum system is governed by the competition between nonadiabatic driving and reservoir-induced relaxation. We study this competition in a driven two-level system weakly coupled to a single thermal reservoir. Using a nonadiabatic time-dependent quantum master equation, we construct the periodic steady state and separate the dissipated work per cycle into population and nonadiabatic contributions in the instantaneous energy basis. The cycle work is nonmonotonic in the driving frequencies studied and is dominated near its maximum by the nonadiabatic contribution. Nonmonotonicity persists in the examined coupling, temperature, and transverse-amplitude scans. At low frequencies, the work recovers the inverse-period scaling of slow-driving thermodynamics. At higher frequencies, the nonadiabatic work rate ceases to grow in proportion to the driving frequency, and the accumulated work per cycle decreases. We also find that, at finite speed, the ratio of the upward and downward transition coefficients is not determined by the instantaneous energy gap alone and obtain the leading correction to instantaneous detailed balance through a short-memory expansion. These results identify how nonadiabatic transitions and relaxation jointly set the thermodynamic cost of sustaining a periodic quantum process.

New Journal of Physics•Sep 30, 2026•0 citations

Finite-size reliability of homothetic quantum Otto engines

Gabriella G. Damas, Clebson Cruz, Norton G. de Almeida +2 more

Homothetic quantum Otto engines---where all populated energy gaps are rescaled by a common factor---provide a reference model in which the quasistatic stochastic efficiency is trajectory-independent while work remains fluctuating. For arbitrary finite homothetic spectra we derive the two-point-measurement work distribution and reduce the first two work moments to endpoint energy moments. Specializing to a uniformly spaced ladder gives closed finite-$N$ expressions for the full work distribution, mean work, variance, and signal-to-width reliability. This ladder connects the qubit and oscillator limits, reveals a finite-$N$ reliability crossover, and demonstrates that the high-temperature and infinite-dimensional limits do not commute. The noncommutation reflects a bounded-versus-unbounded spectral distinction: at fixed finite $N$ the Gibbs state has a normalizable infinite-temperature limit, whereas the oscillator retains an ever-expanding thermal tail. The exact formulas are used to compare standard mean-output prescriptions with work reliability, showing that maximum mean output and maximum dimensionless reliability select different operating points. The benchmark is extended to incomplete diagonal reset and to finite-time unitary strokes described by transition matrices, with a finite-ladder protocol and a harmonic sudden-switch oscillator benchmark as controlled examples. Weak deviations from exact homothety are treated perturbatively, showing how level-dependent gap distortions reintroduce quasistatic efficiency fluctuations and modify work reliability. Together, these results separate finite-size, incomplete thermalization, finite-time, and weak spectral-distortion contributions to work unreliability in quantum Otto engines.

quant-pharXiv:2607.29050•Aug 3, 2026•0 citations

Anomalous transport in quasiperiodic lattices: emergent exceptional points at band edges and log-periodic oscillations

Jinyuan Shang, Haiping Hu

Quasiperiodic systems host exotic transport regimes that are distinct from those found in periodic or disordered lattices. In this work, we study quantum transport in the Aubry-André-Harper lattice in a two-terminal setup coupled to zero-temperature reservoirs, where the conductance is evaluated via the nonequilibrium Green's function method. In the extended phase, we uncover a universal subdiffusive transport when the bath chemical potential aligns with the band edges. Specifically, the typical conductance displays a scaling of $\mathcal{G}_{\text{typ}}\sim L^{-2}$ with system size $L$. We attribute this behavior to the emergence of an exceptional point (Jordan normal form) in the transfer matrix in the thermodynamic limit. In the localized phase, the conductance shows exponential decay governed by the Lyapunov exponent. Intriguingly, in the critical phase, we identify pronounced log-periodic oscillations of the conductance as a function of system size, arising from the discrete scale invariance inherent to the singular-continuous spectrum. We further extend our analysis to the generalized Aubry-André-Harper model and provide numerical evidence suggesting that the exact mobility edge resides within a finite spectral gap. This results in a counter-intuitive exponential suppression of conductance precisely at the mobility edge. Our work highlights the distinct transport behaviors in quasiperiodic systems and elucidates how they are rigorously dictated by the underlying local spectral structure.

cond-mat.mes-hallCross-listedarXiv:2601.10056•Jan 16, 2026
Quasiperiodic systems combine sharply different spectral and localisation regimes with a dense hierarchy of dynamical time scales. We show that a finite-rate quantum Otto cycle can use this structure as a thermodynamic probe, revealing which parts of the spectrum become dynamically accessible and thermodynamically relevant during a driven transformation. For a generalised Aubry-André-Harper chain, the resulting response is not determined by the static quasiperiodic regime alone: extended, near-critical, and crossing protocols do not exhibit universal ordering of work fluctuations. Instead, the statistics reflect transition pathways that are simultaneously dynamically coupled, thermally occupied, and energetically significant. The same spectral accessibility separates thermodynamic recovery from microscopic adiabatic recovery. Positive mean work can reappear while the population transfer dynamics remain strongly nonadiabatic because finite-rate population transfer is redistributed toward energetically less costly channels rather than suppressed. The full work distribution reveals a further separation, with a finite rate window in which positive-work cycles form a majority although the mean work remains negative. This behaviour persists in finite-size analysis. A thermally weighted spectral susceptibility connects these effects to a distributed hierarchy of dynamically active spectral regions rather than to a single minimum-gap bottleneck. Finite thermal contacts preserve this picture while introducing a second time scale and intercycle memory. Quantum Otto cycles can therefore provide a fluctuation-resolved thermodynamic probe of quasiperiodic spectral accessibility, complementary to direct spectroscopic and eigenstate-resolved diagnostics.
We investigate the thermodynamic consequences of longitudinal-transverse cross-spectral reservoir correlations in a finite-time quantum Otto engine with a two-level working medium. Each reservoir couples through excitation-relaxation and dephasing channels whose fluctuations are characterized by a Hermitian positive-semidefinite spectral-density matrix, with the off-diagonal elements encoding their cross correlations. The finite-time isochoric dynamics is derived within the second-order time-convolutionless framework, without imposing the Markov limit at the outset, so that finite reservoir-memory effects can enter through time-dependent dissipative and reservoir-induced coherent contributions. The resulting dynamics is then recast in Bloch-vector form to construct the stroke-resolved cycle dynamics. At fixed auto-spectral densities, cross-spectral correlations modify the populations and coherences of the working medium and thereby its thermodynamic performance. Increasing the correlation strength can enhance the output power, with the enhancement controlled by the cross-spectral phase and characteristic frequency scale. The correlations also reshape the transient cycle-to-cycle evolution and the approach to periodic operation, while the limit-cycle efficiency remains fixed at the Otto value for the population-preserving unitary strokes considered here. These results establish off-diagonal reservoir spectra as an additional resource for controlling finite-time quantum thermal machines.
We show a finite-time Otto-like quantum thermodynamic cycle that preserves the adiabatic population structure of a time-dependent harmonic oscillator in the non-quasi-static regime. In the conventional energy representation, finite-rate driving induces non-adiabatic population redistribution and leaves residual excitations after the Hamiltonian has returned to its initial value. We show that this difficulty can be avoided by formulating the dynamics in the Lewis-Riesenfeld invariant representation, without modifying the physical Hamiltonian through auxiliary counterdiabatic driving. For a parametric Mathieu protocol, quantum inertia produces a mismatch between the spatial width of the working mode and its transient dressed energy scale. We propose an experimental implementation of this scheme in a trapped-ion Paul trap using stimulated Raman interactions, with independent control of the laser detuning and beam intersection angle. This provides a finite-time implementation in which the invariant population structure is preserved while the physical trap frequency evolves non-quasi-statically. Our results establish a clear distinction between adiabatic operation and quasi-static driving, providing a route toward finite-time quantum thermal cycles that retain the adiabatic energy structure without requiring the quasi-static limit.
We systematically investigate the entanglement and information dynamics of quasiperiodic systems across their extended, critical, and localized phases, aiming to identify dynamical signatures that can reveal the multifractal spatial structure of critical states and distinguish critical phases from the extended and localized regimes. Focusing on the generalized Aubry-André-Harper model, we complement the half-chain entanglement entropy with the spatially resolved subsystem information capacity (SIC) and demonstrate that critical states exhibit pronounced spatial heterogeneity absent in the extended and localized phases. In the steady state, the SIC reveals a stepwise ramp as a function of subsystem size, reflecting an underlying fragmentation of the chain into weakly connected subregions. Dynamically, information initially localized within such a subregion can undergo coherent long-lived oscillations, dubbed subregion echoes, whose period scales with the subregion length, in quantitative agreement with a quasiparticle picture of confined quasiparticle reflections. We trace this internal fragmentation to the incommensurately distributed zeros (IDZs) in the off-diagonal hopping terms of the Hamiltonian. To establish the generality of the SIC as a diagnostic tool, we further apply it to a mobility-edge phase with coexisting extended and localized states and to a critical phase that does not originate from IDZ fragmentation, and show that the SIC can cleanly distinguish these scenarios through their distinct steady-state profiles, initial-site sensitivities, and the presence or absence of subregion echoes. Our results demonstrate that the SIC serves as a powerful real-space probe for diagnosing critical phases and uncovering the bottlenecked connectivity that underlies the multifractal structure of critical states.
Abstract Finite-time periodic control of an open quantum system is governed by the competition between nonadiabatic driving and reservoir-induced relaxation. We study this competition in a driven two-level system weakly coupled to a single thermal reservoir. Using a nonadiabatic time-dependent quantum master equation, we construct the periodic steady state and separate the dissipated work per cycle into population and nonadiabatic contributions in the instantaneous energy basis. The cycle work is nonmonotonic in the driving frequencies studied and is dominated near its maximum by the nonadiabatic contribution. Nonmonotonicity persists in the examined coupling, temperature, and transverse-amplitude scans. At low frequencies, the work recovers the inverse-period scaling of slow-driving thermodynamics. At higher frequencies, the nonadiabatic work rate ceases to grow in proportion to the driving frequency, and the accumulated work per cycle decreases. We also find that, at finite speed, the ratio of the upward and downward transition coefficients is not determined by the instantaneous energy gap alone and obtain the leading correction to instantaneous detailed balance through a short-memory expansion. These results identify how nonadiabatic transitions and relaxation jointly set the thermodynamic cost of sustaining a periodic quantum process.
Homothetic quantum Otto engines---where all populated energy gaps are rescaled by a common factor---provide a reference model in which the quasistatic stochastic efficiency is trajectory-independent while work remains fluctuating. For arbitrary finite homothetic spectra we derive the two-point-measurement work distribution and reduce the first two work moments to endpoint energy moments. Specializing to a uniformly spaced ladder gives closed finite-NNN expressions for the full work distribution, mean work, variance, and signal-to-width reliability. This ladder connects the qubit and oscillator limits, reveals a finite-NNN reliability crossover, and demonstrates that the high-temperature and infinite-dimensional limits do not commute. The noncommutation reflects a bounded-versus-unbounded spectral distinction: at fixed finite NNN the Gibbs state has a normalizable infinite-temperature limit, whereas the oscillator retains an ever-expanding thermal tail. The exact formulas are used to compare standard mean-output prescriptions with work reliability, showing that maximum mean output and maximum dimensionless reliability select different operating points. The benchmark is extended to incomplete diagonal reset and to finite-time unitary strokes described by transition matrices, with a finite-ladder protocol and a harmonic sudden-switch oscillator benchmark as controlled examples. Weak deviations from exact homothety are treated perturbatively, showing how level-dependent gap distortions reintroduce quasistatic efficiency fluctuations and modify work reliability. Together, these results separate finite-size, incomplete thermalization, finite-time, and weak spectral-distortion contributions to work unreliability in quantum Otto engines.
Quasiperiodic systems host exotic transport regimes that are distinct from those found in periodic or disordered lattices. In this work, we study quantum transport in the Aubry-André-Harper lattice in a two-terminal setup coupled to zero-temperature reservoirs, where the conductance is evaluated via the nonequilibrium Green's function method. In the extended phase, we uncover a universal subdiffusive transport when the bath chemical potential aligns with the band edges. Specifically, the typical conductance displays a scaling of Gtyp∼L−2\mathcal{G}_{\text{typ}}\sim L^{-2}Gtyp​∼L−2 with system size LLL. We attribute this behavior to the emergence of an exceptional point (Jordan normal form) in the transfer matrix in the thermodynamic limit. In the localized phase, the conductance shows exponential decay governed by the Lyapunov exponent. Intriguingly, in the critical phase, we identify pronounced log-periodic oscillations of the conductance as a function of system size, arising from the discrete scale invariance inherent to the singular-continuous spectrum. We further extend our analysis to the generalized Aubry-André-Harper model and provide numerical evidence suggesting that the exact mobility edge resides within a finite spectral gap. This results in a counter-intuitive exponential suppression of conductance precisely at the mobility edge. Our work highlights the distinct transport behaviors in quasiperiodic systems and elucidates how they are rigorously dictated by the underlying local spectral structure.