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:2508.11606 · Physical Review A

Dependence of the recoherence times and recoherence increments on the state of phonon bath in a single-qubit dephasing model

V. V. Ignatyuk, Ch. Samorodov

Published Dec 2, 2025• 0 citations
arXivHTMLPDF

Abstract

The recoherence times t * and the maximum values of the recoherence increments γ extr are studied as functions of the bath parameters for a single qubit dephasing model, prepared initially by a special kind of the nonselective measurements. The recoherence-decoherence events (RDE), occurring at the initial stage of the system evolution, are found to be both similar and different from the system dynamics at large times. For instance, in contrast to the RDE observed on large timescales, the sub-Ohmic and Ohmic coupling regimes are more favorable for the short-time recoherence than the super-Ohmic one. On the other hand, the short-time behavior of the recoherence and the long-time dynamics of the decoherence are closely related: The domain of the ohmicity indexes, where the decoherence changes its type (from the complete to incomplete one), is, simultaneously, that of the weakest recoherence. The obtained results give us some hints about the basic characteristics of the environment, which might provide the most optimal values of t * and γ extr in some sense.

DOI
10.1103/znt9-lhq9

Related papers

Preparing Decoherence-Recoherence Times of a Qubit with Special Nonselective Measurement Schemes

Filippo Giraldi

The appearance of decoherence-recoherence events is analyzed in a dephasing model of a qubit which interacts with a bosonic environment. The initial condition is prepared from the thermal state of the whole system by performing a nonselective measurement on the qubit. Decoherence-recoherence events appear in the reduced dynamics of the qubit uniquely if special nonselective preparation measurements are adopted and the spectral density of the system fulfills determined conditions. General lower bounds are found for the number of decoherence-recoherence events in terms of the properties of the measurement scheme and of the spectral density. The number is finite for canonical spectral densities which are super-ohmic, perturbed super-ohmic, or ohmic at low frequencies and are arbitrarily tailored at high frequencies. The number is infinite in the sub-ohmic regime and for perturbations of the sub-ohmic or ohmic regime. Decoherence-recoherence times are evaluated, analytically and numerically, for ohmic-like spectral densities with exponential high-frequency cutoffs.

Open Systems & Information Dynamics•Mar 1, 2021•1 citation

Dephasing and pseudocoherent quantum dynamics in super-Ohmic environments

Ph. Nacke, Florian Otterpohl, Michael Thorwart +1 more

Dephasing in quantum systems is typically the result of their interaction with environmental degrees of freedom. We investigate within a spin-boson model the influence of a super-Ohmic environment on the dynamics of a quantum two-state system. A super-Ohmic environment thereby models typical bulk phonons which are a common disturbance for solid state quantum systems as, for example, nitrogen-vacancy centers. By applying the numerically exact quasiadiabatic path-integral approach we show that for strong system-bath coupling, pseudocoherent dynamics emerges, i.e., oscillatory dynamics at short times due to slaving of the quantum system to the bath dynamics. We extend the phase diagram known for sub-Ohmic and Ohmic environments into the super-Ohmic regime and observe a pronounced nonmonotonous behavior. Super-Ohmic purely dephasing fluctuations strongly suppress the amplitude of coherent dynamics at very short times with no subsequent further decay at later times. Nevertheless, they render the dynamics overdamped. The corresponding phase separation line shows also a nonmonotonous behavior, very similar to the pseudocoherent dynamics.

arXiv:2303.18213•Physical Review A•Jun 28, 2023•9 citations

Enhancement of coherence in qubits due to interaction with the environment

V. V. Ignatyuk, V. G. Morozov

The influence of the initial preparation on dephasing in open quantum dynamics is studied using an exactly solvable model of a two-level system (qubit) interacting with a bosonic bath. It is found that, for some classes of nonselective preparation measurements, qubit-bath correlations lead to a significant enhancement of coherence in the qubit at the initial stage of evolution. The time behavior of the qubit purity and entropy in the regime of enhancement of coherence is considered for different temperatures and coupling strengths.

arXiv:1504.05244•Physical Review A•May 6, 2015•12 citations

Non-Markovian dynamics of a dephasing model in a squeezed thermal bath

Zhi He, Hao‐Sheng Zeng, Yu Chen +1 more

Abstract The non-Markovian dynamics of a qubit dephasing in a squeezed thermal environment with general Ohmic spectral density are investigated, and the analytical solution is presented for the models with sub-Ohmic, Ohmic, and super-Ohmic spectral densities in the zero-temperature limit. We study the non-Markovianity of the open qubit system, and find that it is very large in a certain regime of the squeezed parameters and almost vanishes outside this regime, given the parameters of the environmental spectrum. Furthermore, the non-Markovianity can be enhanced to surpass that of the unsqueezed case by adjusting the squeezing parameters. More interestingly, we find that given the other parameters, the non-Markovianity of a small coupling constant between the qubit and its environment may be larger than in the case of a large coupling constant; this is dependent on the competition between the coupling constant and the Ohmicity parameter of the environment. We also discuss the influence of squeezing operator on the quantum speed limit (QSL) time for the considered model, and find that the QSL time can be reduced via the adjustment of the squeezing operator.

Laser Physics Letters•May 13, 2019•6 citations

Non-Markovianity in a dressed qubit with local dephasing

Saima Bashir, Muzaffar Qadir Lone, Prince A Ganai

We study the dynamics of a dressed qubit implemented by a spinless fermion hopping between two lattice sites with each site strongly coupled to a bath of phonons. We employ Lang-Firsov transformation to make the problem tractable perturbatively. Applying time-convolutionless master equation within the polaron frame, we investigate decoherence dynamics of the dressed qubit within the singlet-triplet basis of the system for a wide range of bath spectral densities. It is shown that the coherence persists for longer time scales for large coupling values and shows non-monotonic behaviour reflecting the presence of non-Markovianity in the dynamics. Non-Markovianity, characterized by coherence revivals and non-monotonic decay patterns, emerges distinctly depending on the bath spectrum and coupling strengths. Systems coupled to sub-Ohmic baths, whether both or in combination with another type, display pronounced memory effects at relatively small values of couplings. In contrast, combinations involving Ohmic and super-Ohmic baths exhibit noticeable non-Markovianity only at higher couplings.

quant-pharXiv:2602.07438•Feb 10, 2026•0 citations

Directed Recoherence in Structured Non-Markovian Environments: A Predictable Regime for Passive Coherence Enhancement

Ferreira, Manuel Rui Santos

Directed Recoherence in Structured Non-Markovian Environments presents a rigorously defined operating regime of open quantum system dynamics in which environmental memory leads not to oscillatory revivals, but to directed, monotonic recoherence toward a long-lived metastable coherence plateau. The work introduces a minimal and physically standard two-bath pure-dephasing model composed of a broadband Markovian noise bath and a narrowband non-Markovian reference bath. Within this framework, a dimensionless recoherence parameter R = λ_R² / [ γ_N Γ (1 + (δ/Γ)² ) ] is shown to govern a sharp transition between ordinary decoherence and a directed recoherence regime. When R exceeds a threshold of order unity, the system exhibits a single coherence minimum followed by monotonic recoherence and a metastable phase-locked plateau over experimentally relevant timescales. Exact closed-form solutions for the coherence dynamics are derived, alongside falsifiable predictions including bounded phase deviation relative to the reference bath. Numerical simulations confirm the existence of a critical threshold and distinguish this regime from known non-Markovian revivals, decoherence-free subspaces, driven steady states, and many-body prethermalization. The manuscript reframes Self-Initiated Phase Re-Coherence (SIPR) not as a new physical principle, but as a previously under-characterized regime within standard quantum open-system theory. Potential experimental realizations are discussed for superconducting qubits with Purcell-filtered environments and trapped ions with engineered sidebands. A companion conceptual document explores the epistemic and interpretational implications of measurement, observation, and environmental structure without modifying the physical results presented here.

•Dec 13, 2025•0 citations
The recoherence times t * and the maximum values of the recoherence increments γ extr are studied as functions of the bath parameters for a single qubit dephasing model, prepared initially by a special kind of the nonselective measurements. The recoherence-decoherence events (RDE), occurring at the initial stage of the system evolution, are found to be both similar and different from the system dynamics at large times. For instance, in contrast to the RDE observed on large timescales, the sub-Ohmic and Ohmic coupling regimes are more favorable for the short-time recoherence than the super-Ohmic one. On the other hand, the short-time behavior of the recoherence and the long-time dynamics of the decoherence are closely related: The domain of the ohmicity indexes, where the decoherence changes its type (from the complete to incomplete one), is, simultaneously, that of the weakest recoherence. The obtained results give us some hints about the basic characteristics of the environment, which might provide the most optimal values of t * and γ extr in some sense.
The appearance of decoherence-recoherence events is analyzed in a dephasing model of a qubit which interacts with a bosonic environment. The initial condition is prepared from the thermal state of the whole system by performing a nonselective measurement on the qubit. Decoherence-recoherence events appear in the reduced dynamics of the qubit uniquely if special nonselective preparation measurements are adopted and the spectral density of the system fulfills determined conditions. General lower bounds are found for the number of decoherence-recoherence events in terms of the properties of the measurement scheme and of the spectral density. The number is finite for canonical spectral densities which are super-ohmic, perturbed super-ohmic, or ohmic at low frequencies and are arbitrarily tailored at high frequencies. The number is infinite in the sub-ohmic regime and for perturbations of the sub-ohmic or ohmic regime. Decoherence-recoherence times are evaluated, analytically and numerically, for ohmic-like spectral densities with exponential high-frequency cutoffs.
Dephasing in quantum systems is typically the result of their interaction with environmental degrees of freedom. We investigate within a spin-boson model the influence of a super-Ohmic environment on the dynamics of a quantum two-state system. A super-Ohmic environment thereby models typical bulk phonons which are a common disturbance for solid state quantum systems as, for example, nitrogen-vacancy centers. By applying the numerically exact quasiadiabatic path-integral approach we show that for strong system-bath coupling, pseudocoherent dynamics emerges, i.e., oscillatory dynamics at short times due to slaving of the quantum system to the bath dynamics. We extend the phase diagram known for sub-Ohmic and Ohmic environments into the super-Ohmic regime and observe a pronounced nonmonotonous behavior. Super-Ohmic purely dephasing fluctuations strongly suppress the amplitude of coherent dynamics at very short times with no subsequent further decay at later times. Nevertheless, they render the dynamics overdamped. The corresponding phase separation line shows also a nonmonotonous behavior, very similar to the pseudocoherent dynamics.
The influence of the initial preparation on dephasing in open quantum dynamics is studied using an exactly solvable model of a two-level system (qubit) interacting with a bosonic bath. It is found that, for some classes of nonselective preparation measurements, qubit-bath correlations lead to a significant enhancement of coherence in the qubit at the initial stage of evolution. The time behavior of the qubit purity and entropy in the regime of enhancement of coherence is considered for different temperatures and coupling strengths.
Abstract The non-Markovian dynamics of a qubit dephasing in a squeezed thermal environment with general Ohmic spectral density are investigated, and the analytical solution is presented for the models with sub-Ohmic, Ohmic, and super-Ohmic spectral densities in the zero-temperature limit. We study the non-Markovianity of the open qubit system, and find that it is very large in a certain regime of the squeezed parameters and almost vanishes outside this regime, given the parameters of the environmental spectrum. Furthermore, the non-Markovianity can be enhanced to surpass that of the unsqueezed case by adjusting the squeezing parameters. More interestingly, we find that given the other parameters, the non-Markovianity of a small coupling constant between the qubit and its environment may be larger than in the case of a large coupling constant; this is dependent on the competition between the coupling constant and the Ohmicity parameter of the environment. We also discuss the influence of squeezing operator on the quantum speed limit (QSL) time for the considered model, and find that the QSL time can be reduced via the adjustment of the squeezing operator.
We study the dynamics of a dressed qubit implemented by a spinless fermion hopping between two lattice sites with each site strongly coupled to a bath of phonons. We employ Lang-Firsov transformation to make the problem tractable perturbatively. Applying time-convolutionless master equation within the polaron frame, we investigate decoherence dynamics of the dressed qubit within the singlet-triplet basis of the system for a wide range of bath spectral densities. It is shown that the coherence persists for longer time scales for large coupling values and shows non-monotonic behaviour reflecting the presence of non-Markovianity in the dynamics. Non-Markovianity, characterized by coherence revivals and non-monotonic decay patterns, emerges distinctly depending on the bath spectrum and coupling strengths. Systems coupled to sub-Ohmic baths, whether both or in combination with another type, display pronounced memory effects at relatively small values of couplings. In contrast, combinations involving Ohmic and super-Ohmic baths exhibit noticeable non-Markovianity only at higher couplings.
Directed Recoherence in Structured Non-Markovian Environments presents a rigorously defined operating regime of open quantum system dynamics in which environmental memory leads not to oscillatory revivals, but to directed, monotonic recoherence toward a long-lived metastable coherence plateau. The work introduces a minimal and physically standard two-bath pure-dephasing model composed of a broadband Markovian noise bath and a narrowband non-Markovian reference bath. Within this framework, a dimensionless recoherence parameter R = λ_R² / [ γ_N Γ (1 + (δ/Γ)² ) ] is shown to govern a sharp transition between ordinary decoherence and a directed recoherence regime. When R exceeds a threshold of order unity, the system exhibits a single coherence minimum followed by monotonic recoherence and a metastable phase-locked plateau over experimentally relevant timescales. Exact closed-form solutions for the coherence dynamics are derived, alongside falsifiable predictions including bounded phase deviation relative to the reference bath. Numerical simulations confirm the existence of a critical threshold and distinguish this regime from known non-Markovian revivals, decoherence-free subspaces, driven steady states, and many-body prethermalization. The manuscript reframes Self-Initiated Phase Re-Coherence (SIPR) not as a new physical principle, but as a previously under-characterized regime within standard quantum open-system theory. Potential experimental realizations are discussed for superconducting qubits with Purcell-filtered environments and trapped ions with engineered sidebands. A companion conceptual document explores the epistemic and interpretational implications of measurement, observation, and environmental structure without modifying the physical results presented here.