REVIEW 1 major objections 2 minor 55 references
Sufficiently large nonreciprocity allows colored noise to trigger multiple exceptional points that set the adiabatic tunneling probability in Landau-Zener systems.
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2026-06-30 00:54 UTC pith:73YHHBEK
load-bearing objection For large nonreciprocity, colored noise appears to trigger extra exceptional points that fix the adiabatic tunneling probability, but the numerical extraction of those points may be sensitive to solver details. the 1 major comments →
Nonreciprocal Landau-Zener Tunneling in the Presence of Heat-Bath-Induced Colored Noise
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
In the presence of colored noise, nonreciprocal Landau-Zener tunneling exhibits stochastic fluctuations in instantaneous energy levels. For large enough nonreciprocity parameters, the noise triggers the emergence of multiple exceptional points. The tunneling probability is enhanced by noise in nonadiabatic sweeping and loses reciprocity in the adiabatic limit, but for large nonreciprocity the adiabatic probability is determined solely by these exceptional points and insensitive to noise amplitude or correlation time.
What carries the argument
The nonreciprocity parameter in the Hamiltonian, which controls the asymmetry in the tunneling process and enables noise-induced multiple exceptional points in the complex energy spectrum.
Load-bearing premise
The numerical identification of exceptional points from the stochastic energy levels accurately reflects the true effect of the colored noise without introducing artifacts from the simulation method.
What would settle it
Measuring the adiabatic tunneling probability for varying noise correlation times at large nonreciprocity and finding dependence on those times, or failing to observe additional exceptional points as nonreciprocity increases, would falsify the claim.
If this is right
- Colored noise enhances the nonadiabatic tunneling probability compared to the noiseless case.
- In the adiabatic limit, colored noise breaks the reciprocity of the tunneling probability.
- For large nonreciprocity parameters, the adiabatic tunneling probability is insensitive to noise and solely determined by the locations of exceptional points.
- The phase diagram of tunneling probability versus sweep rate and nonreciprocity parameter shifts with noise amplitude and correlation time.
Where Pith is reading between the lines
- The interaction suggests a way to use nonreciprocity to stabilize tunneling probabilities against noise variations in quantum systems.
- Exceptional points may serve as robust features in non-Hermitian dynamics under stochastic driving.
- Similar effects could appear in other driven non-Hermitian quantum models with asymmetric couplings.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript studies nonreciprocal Landau-Zener tunneling in the presence of heat-bath-induced colored noise. Numerical simulations of the instantaneous eigenvalues of the stochastic non-Hermitian Hamiltonian reveal energy-level fluctuations and, for sufficiently large nonreciprocity parameters, the noise-induced appearance of multiple exceptional points. These features modify the tunneling probability, with colored noise generally enhancing nonadiabatic tunneling while breaking reciprocity in the adiabatic limit; for large nonreciprocity the adiabatic probability becomes insensitive to noise and is controlled by the exceptional points. Phase diagrams are presented as functions of sweep rate and nonreciprocity for varying noise amplitude and correlation time. Analytically, an exact expression for the noise-free case and an approximate solution in the white-noise limit are derived using Weber functions and the Wiener-Hermite expansion.
Significance. If the numerical identification of noise-triggered exceptional points is robust, the work provides a concrete link between colored noise, nonreciprocity, and exceptional-point physics in open quantum systems, extending beyond the white-noise and noise-free limits that are treated analytically. The use of standard special functions and the Wiener-Hermite method supplies reproducible analytic benchmarks, while the phase diagrams offer testable predictions for parameter regimes where noise effects saturate.
major comments (1)
- [numerical calculations of the instantaneous energy levels] Numerical calculations of instantaneous energy levels: the central claim that sufficiently large nonreciprocity parameters allow colored noise to trigger multiple exceptional points (whose locations then control the adiabatic tunneling probability) rests on stochastic eigenvalue trajectories. The manuscript does not specify the coalescence criterion (e.g., minimum eigenvalue separation or winding-number test), the integrator time step, the number of noise realizations, or the interpolation scheme used to locate crossings. Without these controls it is impossible to exclude the possibility that reported multiple EPs are discretization or ensemble artifacts, directly undermining the asserted causal relation between noise, nonreciprocity, and the phase diagram.
minor comments (2)
- [abstract] The abstract states that the adiabatic tunneling probability becomes “insensitive to noise and determined by exceptional points” for large nonreciprocity; a brief quantitative statement of the residual noise dependence (e.g., scaling with correlation time) would strengthen this claim.
- [analytic derivation] The Wiener-Hermite expansion is invoked for the white-noise limit; the truncation order and convergence criterion should be stated explicitly so that readers can reproduce the approximate tunneling probability.
Simulated Author's Rebuttal
We thank the referee for the careful reading of our manuscript and the constructive comments. We address the major comment below.
read point-by-point responses
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Referee: Numerical calculations of instantaneous energy levels: the central claim that sufficiently large nonreciprocity parameters allow colored noise to trigger multiple exceptional points (whose locations then control the adiabatic tunneling probability) rests on stochastic eigenvalue trajectories. The manuscript does not specify the coalescence criterion (e.g., minimum eigenvalue separation or winding-number test), the integrator time step, the number of noise realizations, or the interpolation scheme used to locate crossings. Without these controls it is impossible to exclude the possibility that reported multiple EPs are discretization or ensemble artifacts, directly undermining the asserted causal relation between noise, nonreciprocity, and the phase diagram.
Authors: We acknowledge that the manuscript does not provide the requested details on the numerical procedure for identifying exceptional points. This omission makes it difficult to fully assess the robustness of the results against potential artifacts. In the revised manuscript, we will add a dedicated subsection or paragraph detailing the coalescence criterion (using a combination of eigenvalue separation threshold and winding number analysis), the specific integrator time step employed, the number of noise realizations used for the ensemble, and the interpolation scheme for locating crossings in the eigenvalue trajectories. These additions will enable verification that the multiple exceptional points are physically meaningful rather than numerical artifacts, thereby supporting the claimed connection to the phase diagram. revision: yes
Circularity Check
No circularity: derivations rely on standard analytic methods and independent numerics
full rationale
The paper's analytic results consist of an exact no-noise tunneling probability expressed via Weber functions and a white-noise approximation obtained through the Wiener-Hermite expansion; both are standard techniques applied directly to the given non-Hermitian Hamiltonian and do not reduce to any fitted parameter or self-defined quantity. The colored-noise regime is handled by direct numerical diagonalization of instantaneous eigenvalues, with exceptional-point identification presented as an output of that computation rather than an input. No self-citation is invoked as a load-bearing uniqueness theorem, no ansatz is smuggled via prior work, and no prediction is shown to be equivalent to a fit by construction. The derivation chain is therefore self-contained against external benchmarks.
Axiom & Free-Parameter Ledger
free parameters (2)
- nonreciprocity parameter
- amplitude and correlation time of colored noise
axioms (2)
- domain assumption System dynamics follow a time-dependent nonreciprocal Hamiltonian under stochastic noise
- domain assumption Colored noise is modeled with finite correlation time from a heat bath
read the original abstract
In this work, we investigate the effects of heat-bath-induced colored noise on nonreciprocal Landau-Zener tunneling. We perform numerical calculations of the instantaneous energy levels and find that noise induces stochastic fluctuations in these levels. Beyond such fluctuations, sufficiently large nonreciprocity parameters enable noise to further trigger the emergence of multiple exceptional points. The corresponding tunneling probability is significantly modified by colored noise. On the one hand, colored noise generally enhances the tunneling probability under nonadiabatic sweeping. On the other hand, it can break the reciprocity of Landau-Zener tunneling in the adiabatic limit. In particular, for large nonreciprocity parameters, the adiabatic tunneling probability is insensitive to noise and determined by exceptional points. We plot the phase diagram of tunneling probability as a function of the sweep rate and nonreciprocity parameter, for different amplitudes and correlation times of colored noise. Analytically, we derive the exact expression for the tunneling probability in the absence of noise and an approximate solution in the white-noise limit, employing Weber functions and the Wiener-Hermite expansion method. Some implications of our theory are discussed.
Figures
Reference graph
Works this paper leans on
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For δ > 1, the noise appreciably FIG. 1. Instantaneous energy levels for various nonrecipro c- ity parameters. The black dashed line corresponds to the noiseless case, while the magenta solid line depicts the noi sy counterpart. The red and blue arrows indicate the forward and backward LZ tunneling processes, respectively. shifts the positions of the EPs ...
2000
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[2]
( 5) with the Heun scheme [ 40]
using the fourth-order Runge- Kutta method, during which the noise variable f (t) is generated by solving Eq. ( 5) with the Heun scheme [ 40]. To specify the initial noise values for the ensemble sim- ulations, we consider the time-dependent distribution Φ(f,t ) of the noise variable, whose evolution is gov- erned by the deterministic Fokker-Planck equati...
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[3]
In the weak- noise regime, the tunneling probability remains nearly unaffected even by fast colored noise [see Fig. 3(b)]. In contrast, for strong slow noise, the tunneling probability is distinctly enhanced in the parameter regime of small |α | and δ [see Fig. 3(c)]. For fixed noise amplitude, fur- ther increasing ˜γ drives the system into the fast-noise r...
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[4]
Here the symbol erf denotes the error function
vanishes in this case, the Schr¨ odinger equation can be solved analytically with initial conditions a(−t0) = a0 and b(−t0) = b0, which yields the exact solution a(t0) = a0 + ivb0 √ π 2iα exp ( iαt 2 0 2 ) erf ( √ iα 2t0 ) , b (t0) = b0. Here the symbol erf denotes the error function. Using the asymp- totic limit of the error function as t0 → +∞ and the i...
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[5]
For brevity, we omit the index n = 0 hereafter, namely p(t) ≡ p(0,t ), q(t) ≡ q(0,t ) and r(t) ≡ r(0,t )
by retaining only the equations associated with the n = 0 subspace. For brevity, we omit the index n = 0 hereafter, namely p(t) ≡ p(0,t ), q(t) ≡ q(0,t ) and r(t) ≡ r(0,t ). The resulting coupled equations are presented below ˙p(t) = 1 2v(2 − δ)r(t), (19a) ˙q(t) = − αtr (t) − Γq(t), (19b) ˙r(t) =αtq (t) + 1 2vδs(t) + 1 2v(δ − 2)p(t) − Γr(t), (19c) ˙s(t) =...
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[6]
This incoherent excitation process directly interplays with coherent LZ tunneling, thus raising the overall tunneling probability
Such enhancement originates from heat-bath-induced thermal fluctuations, which drive thermal excitation of the system across the energy gap [ 46]. This incoherent excitation process directly interplays with coherent LZ tunneling, thus raising the overall tunneling probability. When Γ → ∞ and δ = 0, Eqs. (
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[7]
and ( 21) reduce to P (α > 0) = P (α < 0) = 1 2 [ 1 + exp ( − πv 2 |α | )] , which is also obtained by the formal perturbation expansion with respect to the off-diagonal coupling [ 29]. The noise- modulated tunneling probability can decompose into two 0 1 2 Nonreciprocity Parameter: 0 0.2 0.4 0.6 0.8 1 1.2 (a) =-0.1, D=5, =10 0 1 2 Nonreciprocity Parameter...
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[8]
The same adiabatic tunneling probabil- ities were also obtained in Ref. [ 4]. When δ <1 in the adiabatic limit α → ± 0, Eqs. ( 20) and ( 21) reduce to P (α → 0+) = ( δ − 1)/ (δ − 2) and P (α → 0− ) = 1 / (2 − δ), respectively. By contrast, the tunneling probability vanishes without noise. This clearly demonstrates that noise breaks the reciprocity of LZ t...
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