Biorthogonal Dynamical Quantum Phase Transitions in a Non-Hermitian Kitaev Chain
Pith reviewed 2026-05-20 18:01 UTC · model grok-4.3
The pith
Accounting for biorthogonality shifts the critical times at which dynamical quantum phase transitions occur in the non-Hermitian Kitaev chain.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
In the non-Hermitian Kitaev chain, dynamical quantum phase transitions are located by constructing associated states that respect the biorthogonality of left and right eigenvectors. The Loschmidt rate function is then reformulated, along with the dynamical topological order parameter and the positions of dynamical Fisher zeros. The resulting critical times differ from the values given by conventional self-normal approaches, and the same shift appears when subsystems at critical momenta are examined separately.
What carries the argument
The associated-state formalism that pairs states to enforce biorthogonality while reformulating the Loschmidt rate function and dynamical Fisher zeros.
If this is right
- Dynamical Fisher zeros appear at different times once biorthogonality is enforced.
- The dynamical topological order parameter must be redefined to remain consistent with the non-orthogonal inner product.
- Momentum-resolved subsystems at critical momenta continue to exhibit the same shifted transition times.
- Nonequilibrium dynamics of non-Hermitian topological superconductors require the biorthogonal treatment to locate transitions correctly.
Where Pith is reading between the lines
- The same biorthogonal reformulation could be applied to other non-Hermitian lattice models to check for analogous shifts in critical times.
- Experimental protocols that measure Loschmidt echoes in open quantum systems may need to incorporate left-right state pairing to match theoretical predictions.
- The framework suggests a route to connect dynamical transitions with the non-Hermitian topological invariants already studied in equilibrium.
Load-bearing premise
The associated-state construction correctly incorporates biorthogonality without creating artifacts that move the dynamical Fisher zeros.
What would settle it
A direct numerical computation of the biorthogonal Loschmidt echo for the non-Hermitian Kitaev chain that yields the same critical times as the conventional self-normal method.
Figures
read the original abstract
Dynamical quantum phase transitions in non-Hermitian systems pose fundamental challenges due to the intrinsic biorthogonality of their eigenstates. In this work, we extend a biorthogonal framework to investigate dynamical quantum phase transitions in non-Hermitian topological superconductors. Taking the non-Hermitian Kitaev chain as a prototypical model, we construct an associated-state formalism and reformulate the Loschmidt rate function, dynamical topological order parameter, and dynamical Fisher zeros. Within this framework, we find that the critical times at which dynamical quantum phase transitions occur differ from those based on the conventional self-normal approaches. We further analyze momentum-resolved subsystems at critical momenta and demonstrate the robustness of the biorthogonal framework. Our work highlights the essential role of biorthogonality in nonequilibrium dynamics and establishes a consistent theoretical framework for dynamical quantum phase transitions in non-Hermitian topological superconductors.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper extends a biorthogonal framework to dynamical quantum phase transitions (DQPTs) in non-Hermitian topological superconductors, taking the non-Hermitian Kitaev chain as the model. It introduces an associated-state formalism to reformulate the Loschmidt rate function, the dynamical topological order parameter, and the locations of dynamical Fisher zeros. The central result is that the critical times at which DQPTs occur differ from those obtained with conventional self-normalized approaches; the work also examines momentum-resolved subsystems at critical momenta and claims robustness of the biorthogonal construction.
Significance. If the reported shift in critical times is shown to originate from biorthogonality rather than a specific normalization choice, the framework would provide a useful consistent treatment of nonequilibrium dynamics in non-Hermitian systems. The emphasis on associated states and the analysis of subsystems could help clarify how left/right eigenvector structure affects dynamical observables in PT-symmetric or open quantum models.
major comments (2)
- [Biorthogonal Framework] Biorthogonal Framework section: the reformulated Loschmidt rate function is constructed via the associated-state formalism; the manuscript does not demonstrate that the shift in Fisher-zero locations survives under an alternative but equally valid biorthogonal normalization (e.g., a different scaling of the left eigenvectors that preserves the biorthogonal inner product). Without this check the difference could be an artifact of the particular projection chosen rather than a direct consequence of biorthogonality.
- [Results on Critical Times] Results section on critical times: the claim that critical times differ from self-normal approaches is load-bearing, yet the comparison is presented only for the final rate function; an explicit side-by-side plot or table of the conventional versus biorthogonal Loschmidt echo (or its zeros) for the same time-evolved state would be required to isolate the effect.
minor comments (2)
- [Biorthogonal Framework] Notation for the associated states and the biorthogonal inner product should be introduced once with a clear definition before being used in the rate-function expression.
- [Momentum-Resolved Analysis] Figure captions for the momentum-resolved plots should explicitly state the system size and the value of the non-Hermitian parameter used.
Simulated Author's Rebuttal
We thank the referee for the careful reading and constructive comments on our manuscript. We address each major comment below and have revised the manuscript to strengthen the presentation of the biorthogonal framework and the comparisons.
read point-by-point responses
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Referee: Biorthogonal Framework section: the reformulated Loschmidt rate function is constructed via the associated-state formalism; the manuscript does not demonstrate that the shift in Fisher-zero locations survives under an alternative but equally valid biorthogonal normalization (e.g., a different scaling of the left eigenvectors that preserves the biorthogonal inner product). Without this check the difference could be an artifact of the particular projection chosen rather than a direct consequence of biorthogonality.
Authors: We appreciate the referee highlighting this subtlety regarding normalization choices. In the associated-state formalism, the left and right eigenvectors are fixed by the biorthogonality condition, and the Loschmidt rate function is constructed from the associated states. Overall scaling factors that preserve the inner product cancel in the echo amplitude and thus do not shift the Fisher-zero locations. To make this explicit and rule out any possible artifact, we have added a short discussion together with a numerical verification under rescaled left eigenvectors in the revised manuscript. The shift in critical times remains unchanged, confirming it originates from the biorthogonal structure. revision: yes
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Referee: Results section on critical times: the claim that critical times differ from self-normal approaches is load-bearing, yet the comparison is presented only for the final rate function; an explicit side-by-side plot or table of the conventional versus biorthogonal Loschmidt echo (or its zeros) for the same time-evolved state would be required to isolate the effect.
Authors: We agree that a direct visual comparison would better isolate the effect. While the difference in critical times follows from the distinct rate functions and zero locations, we have added a new figure in the revised manuscript that shows the Loschmidt echo versus time for both the conventional self-normalized approach and the biorthogonal associated-state formalism, using the identical time-evolved state. The plot explicitly marks the shifted positions of the dynamical Fisher zeros. revision: yes
Circularity Check
Reformulated Loschmidt rate function shifts critical times by construction of associated-state formalism
specific steps
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self definitional
[Abstract]
"we construct an associated-state formalism and reformulate the Loschmidt rate function, dynamical topological order parameter, and dynamical Fisher zeros. Within this framework, we find that the critical times at which dynamical quantum phase transitions occur differ from those based on the conventional self-normal approaches."
The critical times are located at the dynamical Fisher zeros of the reformulated Loschmidt rate function. Since the rate function itself is redefined via the associated-state formalism to incorporate biorthogonality, any shift in zero locations (and thus critical times) is produced by the reformulation step rather than derived from the model Hamiltonian or time evolution independently of that choice.
full rationale
The paper's central result—that critical times for dynamical quantum phase transitions differ from conventional self-normal approaches—follows directly from the choice to construct an associated-state formalism and use it to redefine the Loschmidt rate function and dynamical Fisher zeros. Because the locations of the zeros are determined by the zeros of this newly reformulated rate function, the reported difference is a definitional consequence of adopting the biorthogonal construction rather than an independent prediction extracted from the underlying time-evolution operator. The abstract presents this difference as a finding within the framework, but no separate validation isolates the effect from the normalization choice itself. This matches the self-definitional pattern without requiring external data fitting.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption Standard quantum mechanics applies to non-Hermitian Hamiltonians with biorthogonal left and right eigenstates
invented entities (1)
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associated-state formalism
no independent evidence
Lean theorems connected to this paper
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IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
we construct an associated-state formalism and reformulate the Loschmidt rate function, dynamical topological order parameter, and dynamical Fisher zeros
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IndisputableMonolith/Foundation/RealityFromDistinction.leanreality_from_one_distinction unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
the critical times at which dynamical quantum phase transitions occur differ from those based on the conventional self-normal approaches
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Forward citations
Cited by 1 Pith paper
-
Unified resonant-manifold framework for dynamical quantum phase transitions
A resonant-manifold framework unifies manifold and branch DQPTs by attributing them to resonances within the initial manifold and with a transitional manifold connected by low-order processes, shown in Z2 LGT quenches.
Reference graph
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discussion (0)
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