arXiv subjects

Alexandre Chaduteau

Publications and source records attributed to Alexandre Chaduteau.

6 recordsLinked to original sources

arXiv2026

Agnostic and efficient detection of $\mathbb{Z}_2$ symmetry-protected topological phases in projected entangled-pair states

Symmetry-protected topological (SPT) phases are the simplest example of quantum phases that cannot be detected by local order parameters. Their classification is by now well-established from multiple perspectives, a prominent one being via tensor network states. The practical question, however, is not mere classification, but detection: given the ground state of an interacting Hamiltonian and a symmetry group $G$ along with its representation, is there an efficient way to tell if the state is in a SPT phase with respect to $G$? While there exist such practical tests in one spatial dimension (1D), methods in 2D have so far been restricted to finite-size systems or require an explicit form of virtual symmetries of the tensor networks representing the ground state. Here, we develop an agnostic and efficient method to detect interacting $\mathbb{Z}_2$ 2D SPT phases, using an infinite projected entangled-pair (PEPS) representation of the ground state. The method is agnostic to the symmetry representation in the virtual space of the PEPS tensor and applicable independent of the bond dimension of the tensors. Moreover, it is efficient as it does not require finite-size scalings: it works directly in the thermodynamic limit. We numerically demonstrate the procedure by mapping out phase boundaries away from fixed-point wavefunctions. We extract the SPT label cocycle data explicitly from the PEPS tensor.

cond-mat.str-el↗

arXiv2026

Noise-Induced Topology in Chiral Quantum Walks

Noise typically destroys quantum coherence and washes out transport phenomena that rely on interference. Chiral quantum walks are a case in point: a particle hopping on a lattice threaded by a magnetic flux can spread asymmetrically due to interference between paths, an asymmetry that noise is expected to erase. Remarkably, we find that the most ubiquitous noise -- random fluctuations of on-site energies (dephasing) -- instead renders this asymmetry topologically robust. The density profile develops a skewness that grows in time while its center stays fixed, and in a finite chain the late-time relaxation modes pile up at one edge: a skin effect lacking the drift of conventional non-Hermitian skin effects. With multiple sites per unit cell, the dephasing strength alone can cause a topological phase transition, reversing the asymmetry. On a flux ladder with noisy rung hopping, the noise causes a drift of rung coherences, a quantum ratchet with no classical counterpart. Underlying these effects, the noise-averaged dynamics is an interacting (generically non-integrable) Lindbladian that remains analytically tractable. The modes governing late-time relaxation are bound states of the noise-induced interaction and form a band with a point gap, absent both without noise and under postselection, whose winding number fixes the direction of the asymmetry. These effects are within reach of several experimental platforms, including synthetic lattices, superconducting qubits, and optical lattices.

quant-ph↗

arXiv2026

Topological Dislocation Response in Elementary Semiconductors

We study elementary semiconductors and insulators that are symmetric under spatial inversion: silicon, diamond, germanium, and black phosphorene. These materials are ideal candidates for realizing obstructed atomic insulators, which differ from trivial atomic insulators by a quantized spatial shift of their electronic Wannier centers with respect to the atomic lattice. We use symmetry indicator invariants that allow the prediction of non-trivial responses to crystal dislocations in these materials. We find that edge dislocations generically exhibit a non-trivial response, while screw dislocations always display a trivial response. With the aid of numerical simulations of realistic tight-binding models, we confirm the presence of mid-gap polarization bands localized along dislocations in silicon, diamond, and germanium.

cond-mat.mes-hall↗

arXiv2026

Topology from Decoherence

Decoherence is conventionally regarded as an obstacle to realizing topological quantum phases. This has motivated extensive efforts to suppress noise in candidate topological materials and devices. Here, we show that decoherence can instead induce topological phenomena. We demonstrate this in a lattice system subject to environment-induced dephasing. The noise-averaged dynamics, governed by an interacting quantum master equation, realize a topological phase characterized by a winding number and the non-Hermitian skin effect. The dynamical consequence is striking: the correlated nature of the stochastic noise yields asymmetric diffusion, whose direction is fixed by the winding number and is reversible only through a topological phase transition. This effect is induced purely by interactions, distinguishing it from previous studies of free, effectively single-particle systems. It also disappears upon postselecting measurement outcomes, confirming that it is a genuinely open-system phenomenon with no effective Hamiltonian description. Remarkably, the model remains analytically tractable. Our results establish correlated quantum noise as a route to topology in open many-body systems, beyond free-particle and non-Hermitian Hamiltonian paradigms.

quant-ph↗

arXiv2026

Lindbladian versus Postselected Non-Hermitian Topology

The recent topological classification of non-Hermitian `Hamiltonians' is usually interpreted in terms of pure quantum states that decay or grow with time. However, many-body systems with loss and gain are typically better described by mixed-state open quantum dynamics, which only correspond to pure-state non-Hermitian dynamics upon a postselection of measurement outcomes. Since postselection becomes exponentially costly with particle number, we here investigate to what extent the most important example of non-Hermitian topology can survive without it: the non-Hermitian skin effect and its relationship to a bulk winding number in one spatial dimension. After defining the winding number of the Lindbladian superoperator for a quadratic fermion system, we systematically relate it to the winding number of the associated postselected non-Hermitian Hamiltonian. We prove that the two winding numbers are equal (opposite) in the absence of gain (loss), and provide a physical explanation for this relationship. When both loss and gain are present, the Lindbladian winding number typically remains quantized and non-zero, though it can change sign at a phase transition separating the loss and gain-dominated regimes. This transition, which leads to a reversal of the Lindbladian skin effect localization, is rendered invisible by postselection. We also identify a case where removing postselection induces a skin effect from otherwise topologically trivial non-Hermitian dynamics.

quant-ph↗

arXiv2025

Momentum-space modulated symmetries in the Luttinger liquid

The chiral Luttinger liquid develops quantum chaos as soon as a -- however slight -- nonlinear dispersion is introduced for the microscopic electronic degrees of freedom. For this nonlinear version of the model, we identify an infinite family of translation-invariant interaction potentials with corresponding modulated symmetries. These symmetries are highly unconventional: they are modulated in momentum space (and do not seem to have an easy physical interpretation). We develop a systematic understanding of these symmetries and study the resulting blocks in the Hamiltonian. In particular, this approach allows us to predict the analytic Hamiltonian block sizes and derive asymptotic scaling laws in the limit of large total momentum. These blocks are reminiscent of Hilbert space fragmentation in that, even though they are labeled by a symmetry, this symmetry is highly nonlocal and does not have a simple interpretation. We corroborate this result by studying entanglement entropy and level statistics.

cond-mat.str-el↗