pith. sign in

arxiv: 2606.27043 · v1 · pith:R3ZDGVQTnew · submitted 2026-06-25 · ⚛️ physics.optics · cond-mat.mes-hall· quant-ph

Observation of Non-Hermitian Skin Dynamics in the Liouvillian Regime

Shu Yang , Yeyang Sun , Lingrui Hong , Yi Yang This is my paper

Pith reviewed 2026-06-26 02:28 UTC · model grok-4.3

classification ⚛️ physics.optics cond-mat.mes-hallquant-ph
keywords non-Hermitian skin effectLiouvillian dynamicsopen quantum walksphotonic mesh latticedephasingcenter-of-mass driftnon-reciprocal transportquantum channel simulation
0
0 comments X

The pith

Non-Hermitian skin dynamics in a photonic lattice reveal a crossover from coherence-enhanced to decoherence-enhanced transport in open quantum walks.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper implements a tunable open-system quantum walk on a photonic mesh lattice by combining controlled phase noise for adjustable dephasing with independent non-reciprocal gain-loss imbalance. This platform continuously varies the degree of coherence while tracking directional transport via non-Hermitian skin dynamics. Center-of-mass drift measurements show a clear crossover: transport is first enhanced by coherence and then enhanced by decoherence as phase noise increases. The observed behavior matches quantum-channel simulations and extends to programmed spatial and temporal interfaces that produce accumulation and instantaneous-channel-governed long-time drift.

Core claim

In the Liouvillian regime realized by the photonic mesh lattice, non-Hermitian skin dynamics serve as a probe that measures center-of-mass drift across independent coherence and non-Hermiticity parameters, directly demonstrating a crossover from coherence-enhanced to decoherence-enhanced transport together with programmable interface accumulation and instantaneous-channel drift.

What carries the argument

Non-Hermitian skin dynamics used as a probe of center-of-mass drift in the tunable Liouvillian open-system quantum walk.

If this is right

  • Directional transport evolves continuously from coherent quantum walks to incoherent classical walks.
  • Spatial and temporal interfaces can be programmed to produce accumulation and long-time drift governed by the instantaneous channel.
  • Decoherence actively reshapes non-Hermitian transport rather than only degrading it.
  • The photonic platform enables quantitative simulation of open quantum dynamics that matches quantum-channel theory.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same crossover might appear in other dissipative platforms if non-Hermitian skin modes remain measurable.
  • Programmable interfaces could be used to steer transport in noisy quantum networks by tuning dephasing locally.
  • The observed decoherence enhancement suggests that controlled noise could improve directed transport in certain open-system devices.

Load-bearing premise

The controlled phase noise and non-reciprocal gain-loss imbalance in the photonic mesh lattice accurately realize the intended tunable open-system quantum walk without significant uncontrolled environmental effects.

What would settle it

A direct measurement of center-of-mass drift that shows no crossover from coherence-enhanced to decoherence-enhanced transport when the coherence parameter is varied while holding non-Hermiticity fixed.

Figures

Figures reproduced from arXiv: 2606.27043 by Lingrui Hong, Shu Yang, Yeyang Sun, Yi Yang.

Figure 1
Figure 1. Figure 1: Non-Hermitian quantum walk in the Liouvillian regime and its photonic implementation with tunable decoherence. (a) Schematic of the discrete one-dimensional non-reciprocal quantum walk model under decoherence. The two directional components of the walker experience asymmetric amplification or attenuation controlled by the non-Hermiticity parameter γ. Environmental coupling induces decoherence (indicated by… view at source ↗
Figure 2
Figure 2. Figure 2: Observation of non-Hermitian skin dynamics under tunable decoherence and non-Hermiticity. (a-d) Measured normalized probability distributions P(m, n) of the right-loop component for different combinations of η and γ, where the degree of coherence η is tuned by adjusting the amplitude of the Gaussian noise applied to the PMs, while the non-Hermiticity γ is controlled by reducing the transmittance of the AM … view at source ↗
Figure 3
Figure 3. Figure 3: Drift velocity of the non-Hermitian skin dynamics in the Liouvillian regime. (a) Numerically simulated drift velocity Vdrift (lattice constant and round-trip time are both chosen as unity) as a function of the non-Hermiticity parameter γ and the degree of coherence η. The green dotted lines indicate the parameter cuts measured experimentally in (b) and (c). (b) Drift velocity as a function of γ for several… view at source ↗
Figure 4
Figure 4. Figure 4: (c), where the c.m. first drifts toward the interface and then remains localized near it within the experimental time window. The reversal of the accumulation direction between the two mirror-symmetric configurations further rules out a fixed directional bias of the setup and confirms that the local￾ [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
read the original abstract

Open quantum systems generally do not perfectly preserve phase coherence: coupling to uncontrolled environments requires a density-matrix description based on the Liouvillian framework beyond pure-state wave evolution. Realizing and probing such dynamics in a programmable platform is therefore essential for connecting coherent physics to realistic dissipative settings. Here we implement a tunable open-system quantum walk in a photonic mesh lattice, where controlled phase noise produces adjustable dephasing and non-reciprocal gain-loss imbalance provides an independently tunable non-Hermitian drive. This allows us to continuously interpolate between coherent quantum walks and incoherent classical walks, and to observe how directional transport evolves in the Liouvillian regime. Using non-Hermitian skin dynamics as a probe, we measure the center-of-mass drift over both the coherence and non-Hermiticity parameters, revealing a crossover from coherence-enhanced to decoherence-enhanced transport in quantitative agreement with quantum-channel simulations. We further program spatial and temporal interfaces to demonstrate interface accumulation and a long-time drift governed by the instantaneous channel. Our results establish a controllable photonic platform for simulating open quantum dynamics and show that decoherence can actively reshape non-Hermitian transport.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The manuscript reports an experimental implementation of a tunable open-system quantum walk in a photonic mesh lattice. Controlled phase noise introduces adjustable dephasing while non-reciprocal gain-loss imbalance provides an independent non-Hermitian drive, allowing continuous interpolation between coherent quantum walks and incoherent classical walks. Using non-Hermitian skin dynamics as a probe, the authors measure center-of-mass drift across coherence and non-Hermiticity parameters, reporting a crossover from coherence-enhanced to decoherence-enhanced transport in quantitative agreement with quantum-channel simulations. They further demonstrate interface accumulation at spatial and temporal boundaries and long-time drift governed by the instantaneous channel.

Significance. If the experimental controls realize the intended Liouvillian dynamics without significant uncontrolled effects, the work provides a programmable photonic platform for simulating open quantum systems and shows that decoherence can actively reshape non-Hermitian transport. This bridges coherent and dissipative regimes in a controllable setting.

major comments (2)
  1. [Abstract] Abstract: The claim of 'quantitative agreement with quantum-channel simulations' is presented without any reported error bars, statistical methods, data exclusion criteria, or verification of lattice parameters, preventing assessment of whether the data support the stated agreement.
  2. [Results] Results section (center-of-mass drift measurements): The interpretation of the observed crossover as Liouvillian dynamics rests on the assumption that the phase noise and gain-loss controls accurately realize the intended open-system quantum walk without significant modeling mismatches or environmental effects; explicit validation of this assumption is required for the central claim.
minor comments (1)
  1. [Methods] Clarify in the methods how the quantum-channel simulations are parameterized to match the experimental controls of phase noise and gain-loss imbalance.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their detailed review and constructive feedback on our manuscript. We address each major comment below and indicate the revisions planned for the resubmitted version.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The claim of 'quantitative agreement with quantum-channel simulations' is presented without any reported error bars, statistical methods, data exclusion criteria, or verification of lattice parameters, preventing assessment of whether the data support the stated agreement.

    Authors: We agree that the abstract would benefit from greater precision on this point. In the revised manuscript we will update the abstract to state that the quantitative agreement refers to the center-of-mass drift data shown in the Results section, where error bars represent the standard deviation over repeated experimental runs and the statistical methods are described in the Methods. Lattice-parameter verification will be added to the supplementary information. revision: yes

  2. Referee: [Results] Results section (center-of-mass drift measurements): The interpretation of the observed crossover as Liouvillian dynamics rests on the assumption that the phase noise and gain-loss controls accurately realize the intended open-system quantum walk without significant modeling mismatches or environmental effects; explicit validation of this assumption is required for the central claim.

    Authors: We acknowledge that explicit validation strengthens the central claim. In the revised manuscript we will add a dedicated subsection (or expanded Methods) that presents direct comparisons between measured dephasing rates and the intended Liouvillian rates, limiting-case checks against coherent and fully incoherent walks, and controls for residual environmental effects. These additions will be supported by new figures or panels. revision: yes

Circularity Check

0 steps flagged

No significant circularity

full rationale

The paper is an experimental observation of non-Hermitian skin dynamics in a photonic mesh lattice realizing tunable Liouvillian dynamics via controlled phase noise and gain-loss imbalance. The central result is a measured crossover in center-of-mass drift, reported in quantitative agreement with separate quantum-channel simulations. No derivation chain, parameter fitting presented as prediction, self-citation load-bearing premise, or ansatz smuggling is present in the abstract or described protocol; the claims rest on direct experimental control and external simulation comparison rather than any reduction to inputs by construction.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

No free parameters, axioms, or invented entities are identifiable from the abstract alone; the work relies on standard quantum-channel and non-Hermitian physics concepts.

pith-pipeline@v0.9.1-grok · 5737 in / 1118 out tokens · 44924 ms · 2026-06-26T02:28:39.246934+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

63 extracted references · 1 linked inside Pith

  1. [1]

    Breuer and F

    H.-P. Breuer and F. Petruccione,The theory of open quantum systems(OUP Oxford, 2002)

    2002

  2. [2]

    W. H. Zurek, Reviews of Modern Physics75, 715 (2003)

    2003

  3. [3]

    W. H. Zurek, Physics Today44, 36 (1991)

    1991

  4. [4]

    Lindblad, Communications in Mathematical Physics48, 119 (1976)

    G. Lindblad, Communications in Mathematical Physics48, 119 (1976)

    1976

  5. [5]

    Gorini, A

    V . Gorini, A. Kossakowski, and E. C. G. Sudarshan, Journal of Mathematical Physics17, 821 (1976)

    1976

  6. [6]

    Diehl, E

    S. Diehl, E. Rico, M. A. Baranov, and P. Zoller, Nature Physics 7, 971 (2011)

    2011

  7. [7]

    Verstraete, M

    F. Verstraete, M. M. Wolf, and J. Ignacio Cirac, Nature Physics 5, 633 (2009)

    2009

  8. [8]

    El-Ganainy, K

    R. El-Ganainy, K. G. Makris, M. Khajavikhan, Z. H. Mussli- mani, S. Rotter, and D. N. Christodoulides, Nature Physics14, 11 (2018)

    2018

  9. [9]

    Ashida, Z

    Y . Ashida, Z. Gong, and M. Ueda, Advances in Physics69, 249 (2020)

    2020

  10. [10]

    E. J. Bergholtz, J. C. Budich, and F. K. Kunst, Reviews of Mod- ern Physics93, 015005 (2021)

    2021

  11. [11]

    K. Ding, C. Fang, and G. Ma, Nature Reviews Physics4, 745 (2022)

    2022

  12. [12]

    Yao and Z

    S. Yao and Z. Wang, Physical Review Letters121, 086803 (2018)

    2018

  13. [13]

    Helbig, T

    T. Helbig, T. Hofmann, S. Imhof, M. Abdelghany, T. Kiess- ling, L. W. Molenkamp, C. H. Lee, A. Szameit, M. Greiter, and R. Thomale, Nature Physics16, 747 (2020)

    2020

  14. [14]

    Weidemann, M

    S. Weidemann, M. Kremer, T. Helbig, T. Hofmann, A. Steg- maier, M. Greiter, R. Thomale, and A. Szameit, Science368, 311 (2020)

    2020

  15. [15]

    Okuma, K

    N. Okuma, K. Kawabata, K. Shiozaki, and M. Sato, Physical Review Letters124, 086801 (2020)

    2020

  16. [16]

    Zhang, T

    X. Zhang, T. Zhang, M.-H. Lu, and Y .-F. Chen, Advances in Physics: X7, 2109431 (2022)

    2022

  17. [17]

    Okuma and M

    N. Okuma and M. Sato, Annual Review of Condensed Matter Physics14, 83 (2023)

    2023

  18. [18]

    J. T. Gohsrich, A. Banerjee, and F. K. Kunst, Europhysics Let- ters150, 60001 (2025)

    2025

  19. [19]

    D. S. Borgnia, A. J. Kruchkov, and R.-J. Slager, Physical Re- view Letters124, 056802 (2020)

    2020

  20. [20]

    Zhang, Z

    K. Zhang, Z. Yang, and C. Fang, Physical Review Letters125, 126402 (2020)

    2020

  21. [21]

    H.-Y . Wang, F. Song, and Z. Wang, Physical Review X14, 021011 (2024)

    2024

  22. [22]

    Regensburger, C

    A. Regensburger, C. Bersch, B. Hinrichs, G. Onishchukov, A. Schreiber, C. Silberhorn, and U. Peschel, Physical Review Letters107, 233902 (2011)

    2011

  23. [23]

    M.-A. Miri, A. Regensburger, U. Peschel, and D. N. Christo- doulides, Physical Review A—Atomic, Molecular, and Optical Physics86, 023807 (2012)

    2012

  24. [24]

    Wimmer, A

    M. Wimmer, A. Regensburger, M.-A. Miri, C. Bersch, D. N. Christodoulides, and U. Peschel, Nature Communications6, 7782 (2015)

    2015

  25. [25]

    Weidemann, M

    S. Weidemann, M. Kremer, S. Longhi, and A. Szameit, Nature 601, 354 (2022)

    2022

  26. [26]

    Marques Muniz, F

    A. Marques Muniz, F. Wu, P. Jung, M. Khajavikhan, D. Chris- todoulides, and U. Peschel, Science379, 1019 (2023)

    2023

  27. [27]

    L. Yu, H. Xue, R. Guo, E. A. Chan, Y . Y . Terh, C. Soci, B. Zhang, and Y . Chong, Nature632, 63 (2024)

    2024

  28. [28]

    J. Feis, S. Weidemann, T. Sheppard, H. M. Price, and A. Szameit, Nature Photonics19, 518 (2025)

    2025

  29. [29]

    Z. Pang, O. Abdelghani, M. Solja ˇci´c, and Y . Yang, Optica12, 1794 (2025)

    2025

  30. [30]

    Schreiber, K

    A. Schreiber, K. N. Cassemiro, V . Potoˇcek, A. G´abris, P. J. Mos- ley, E. Andersson, I. Jex, and C. Silberhorn, Physical Review Letters104, 050502 (2010)

    2010

  31. [31]

    Schreiber, K

    A. Schreiber, K. Cassemiro, V . Potoˇcek, A. G ´abris, I. Jex, and C. Silberhorn, Physical Review Letters106, 180403 (2011)

    2011

  32. [32]

    Regensburger, C

    A. Regensburger, C. Bersch, M.-A. Miri, G. Onishchukov, D. N. Christodoulides, and U. Peschel, Nature488, 167 (2012)

    2012

  33. [33]

    Boutari, A

    J. Boutari, A. Feizpour, S. Barz, C. D. Franco, M. Kim, W. Kolthammer, and I. Walmsley, Journal of Optics18, 094007 (2016)

    2016

  34. [34]

    Neves and G

    L. Neves and G. Puentes, Entropy20, 731 (2018)

    2018

  35. [35]

    Longhi, Light: Science & Applications13, 95 (2024)

    S. Longhi, Light: Science & Applications13, 95 (2024)

    2024

  36. [36]

    K. Wang, L. Xiao, S. Longhi, and P. Xue, arXiv preprint arXiv:2604.12739 (2026)

    Pith/arXiv arXiv 2026

  37. [37]

    Kitagawa, E

    T. Kitagawa, E. Berg, M. Rudner, and E. Demler, Physical Re- view B—Condensed Matter and Materials Physics82, 235114 (2010)

    2010

  38. [38]

    J. K. Asb ´oth and H. Obuse, Physical Review B88, 121406 (2013)

    2013

  39. [39]

    M. S. Rudner, N. H. Lindner, E. Berg, and M. Levin, Physical Review X3, 031005 (2013)

    2013

  40. [40]

    Yokomizo and S

    K. Yokomizo and S. Murakami, Physical Review Letters123, 066404 (2019)

    2019

  41. [41]

    M. A. Nielsen and I. L. Chuang,Quantum computation and quantum information(Cambridge university press, 2010)

    2010

  42. [42]

    F. Song, S. Yao, and Z. Wang, Physical Review Letters123, 170401 (2019)

    2019

  43. [43]

    P. G. Kwiat, A. J. Berglund, J. B. Altepeter, and A. G. White, Science290, 498 (2000)

    2000

  44. [44]

    T. A. Brun, H. A. Carteret, and A. Ambainis, Physical Review 7 A67, 032304 (2003)

    2003

  45. [45]

    T. A. Brun, H. A. Carteret, and A. Ambainis, Physical Review Letters91, 130602 (2003)

    2003

  46. [46]

    Ko ˇs´ık, V

    J. Ko ˇs´ık, V . Bu ˇzek, and M. Hillery, Physical Review A—Atomic, Molecular, and Optical Physics74, 022310 (2006)

    2006

  47. [47]

    Kendon, Mathematical Structures in Computer Science17, 1169 (2007)

    V . Kendon, Mathematical Structures in Computer Science17, 1169 (2007)

    2007

  48. [48]

    J. D. Whitfield, C. A. Rodr ´ıguez-Rosario, and A. Aspuru- Guzik, Physical Review A—Atomic, Molecular, and Optical Physics81, 022323 (2010)

    2010

  49. [49]

    Annabestani, S

    M. Annabestani, S. J. Akhtarshenas, and M. R. Abolhassani, Physical Review A—Atomic, Molecular, and Optical Physics 81, 032321 (2010)

    2010

  50. [50]

    M. A. Broome, A. Fedrizzi, B. P. Lanyon, I. Kassal, A. Aspuru- Guzik, and A. G. White, Physical Review Letters104, 153602 (2010)

    2010

  51. [51]

    Geraldi, A

    A. Geraldi, A. Laneve, L. D. Bonavena, L. Sansoni, J. Ferraz, A. Fratalocchi, F. Sciarrino, ´A. Cuevas, and P. Mataloni, Phys- ical Review Letters123, 140501 (2019)

    2019

  52. [52]

    Huang, L

    X. Huang, L. Xiao, B. Huo, X. Wang, S. Longhi, and P. Xue, arXiv preprint arXiv:2606.15935 (2026)

    arXiv 2026

  53. [53]

    Kraus, A

    K. Kraus, A. B ¨ohm, J. D. Dollard, and W. Wootters,States, ef- fects, and operations fundamental notions of quantum theory: Lectures in mathematical physics at the university of Texas at Austin(Springer, 1983)

    1983

  54. [54]

    M. S. Rudner and L. Levitov, Physical Review Letters102, 065703 (2009)

    2009

  55. [55]

    Longhi, Physical Review B102, 201103 (2020)

    S. Longhi, Physical Review B102, 201103 (2020)

    2020

  56. [56]

    C.-H. Liu, K. Zhang, Z. Yang, and S. Chen, Physical Review Research2, 043167 (2020)

    2020

  57. [57]

    T. Haga, M. Nakagawa, R. Hamazaki, and M. Ueda, Physical Review Letters127, 070402 (2021)

    2021

  58. [58]

    Okuma and M

    N. Okuma and M. Sato, Physical Review B103, 085428 (2021)

    2021

  59. [59]

    Yang, Q.-D

    F. Yang, Q.-D. Jiang, and E. J. Bergholtz, Physical Review Re- search4, 023160 (2022)

    2022

  60. [60]

    Kawabata, T

    K. Kawabata, T. Numasawa, and S. Ryu, Physical Review X13, 021007 (2023)

    2023

  61. [61]

    Ekman and E

    C. Ekman and E. J. Bergholtz, Physical Review Research6, L032067 (2024)

    2024

  62. [62]

    Y .-M. Hu, Z. Wang, B. Lian, and Z. Wang, Physical Review Letters135, 260401 (2025)

    2025

  63. [63]

    Longhi, Quantum Science and Technology11, 025042 (2026)

    S. Longhi, Quantum Science and Technology11, 025042 (2026)

    2026