Bias in Local Spin Measurements from Deformed Symmetries

• URL: http://arxiv.org/abs/2603.08618v1
• Date: Mon, 09 Mar 2026 17:02:02 GMT
• Title: Bias in Local Spin Measurements from Deformed Symmetries
• Abstract summary: We study bipartite spin-singlet correlations when rotational symmetry is described by a quantum group rather than an ordinary Lie group.<n>We show that, even though the single-spin observables act as in the undeformed theory, the non-trivial coproduct reshapes the notion of "total" symmetry.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: We study bipartite spin-singlet correlations when rotational symmetry is described by a quantum group rather than an ordinary Lie group. We show that, even though the single-spin observables act as in the undeformed theory, the non-trivial coproduct reshapes the notion of "total" symmetry and leads to a deformed analogue of the Bell singlet state. We show that implementing local measurements with the conventional tensor-factor observables yields a striking effect: perfect anticorrelation is preserved, yet the one-site outcome statistics become deformation-dependent and biased. Using instead the symmetry-covariant, R-matrix-dressed embedding of local observables restores unbiased statistics while maintaining perfect anticorrelation. Our results demonstrate that, in a quantum group symmetry setting, strict tensor-factor locality is not stable under the symmetry and must be replaced by a braided notion of locality to formulate consistent local measurements.

Related papers

• Synchronized Spin Trajectories under Collective Weak Measurements [3.177798986999024]
  Locally driven quantum spins undergo a continuous weak measurement of their collective spin.<n>We show that such a system can exhibit full spin-synchronization in trajectories corresponding to the same measurement record.
  arXiv  Detail & Related papers  (2026-09-11T11:36:56Z)
• Symmetry Constrained Quantum Error Mitigation for the Schwinger Model [39.146761527401424]
  We exploit the parity and fermion-number symmetries of a gauge theory under depolarising noise.<n>We investigate symmetry verification under digital quantum simulation.
  arXiv  Detail & Related papers  (2026-08-21T13:49:11Z)
• Universality of Measurement-Induced Criticality under Symmetry-Breaking Measurements [0.15293427903448023]
  We study the critical properties of random quantum circuits with a $U(1)$ symmetry subject to local projective measurements.<n>We find that, at the measurement-induced phase transition, symmetry-breaking measurements act as a relevant perturbation at large scales.
  arXiv  Detail & Related papers  (2026-07-09T15:24:48Z)
• Average Equilibration Time for Gaussian Unitary Ensemble Hamiltonians [35.18016233072556]
  We study equilibration times in closed quantum systems using the framework of equilibration as dephasing.<n>We find that the equilibration time decreases with system size and timescales in the thermodynamic limit.<n>This unphysical result indicates that the true equilibration timescale of realistic chaotic many-body systems must be dominated by physical features not captured by random matrix ensembles.
  arXiv  Detail & Related papers  (2026-03-30T15:35:04Z)
• Typical entanglement in anyon chains: Page curves beyond Lie group symmetries [41.99844472131922]
  We study bipartite entanglement statistics in one-dimensional anyon chains constrained by fusion rules of unitary pre-modular categories.<n>Surprisingly, despite the constrained Hilbert space structure, the large $L$ expansion has no universal $O(sqrtL)$ or $O(1)$ symmetry-type corrections.<n> Numerical simulations of the integrable and quantum-chaotic golden chain Hamiltonian show that chaotic mid-spectrum eigenstates match the Haar-random predictions.
  arXiv  Detail & Related papers  (2026-03-26T18:00:03Z)
• Symmetric Resourceful Steady States via Non-Markovian Dissipation [0.0]
  We prove a no-go theorem for symmetry-based dissipative engineering of collective-spin steady states.<n>We show that bath memory lifts this obstruction, enabling unique entangled steady states with a prescribed symmetry and a metrological gain.
  arXiv  Detail & Related papers  (2026-03-20T16:15:18Z)
• Freeness Reined in by a Single Qubit [36.94429692322632]
  We find that, even in this setting, the correlation functions predicted by free probability theory receive corrections of order $O(1)$.<n>We trace their origin to non-uniformly distributed stationary quantum states, which we characterize analytically and confirm numerically.
  arXiv  Detail & Related papers  (2025-12-15T19:00:09Z)
• Translation symmetry restoration in integrable systems: the noninteracting case [0.16385815610837165]
  We study translation symmetry restoration in integrable systems.<n>In particular, we consider non-interacting spinless fermions on the lattice prepared in non-equilibrium states invariant under $nu>1$ lattice shifts.<n>We show that, differently from random unitary circuits where symmetry restoration occurs abruptly for times proportional to the subsystem size, here symmetry is restored smoothly and over timescales of the order of the subsystem size squared.
  arXiv  Detail & Related papers  (2025-06-17T14:11:31Z)
• AtlasD: Automatic Local Symmetry Discovery [27.793766164323532]
  This paper formalizes the notion of local symmetry as atlas equivariance.<n>Our proposed pipeline, automatic local symmetry discovery (AtlasD), recovers the local symmetries of a function by training local predictor networks.<n>The discovered local symmetry is shown to be a useful inductive bias that improves the performance of downstream tasks in climate segmentation and vision tasks.
  arXiv  Detail & Related papers  (2025-04-15T00:41:55Z)
• Symmetries, Conservation Laws and Entanglement in Non-Hermitian Fermionic Lattices [37.69303106863453]
  Non-Hermitian quantum many-body systems feature steady-state entanglement transitions driven by unitary dynamics and dissipation.<n>We show that the steady state is obtained by filling single-particle right eigenstates with the largest imaginary part of the eigenvalue.<n>We illustrate these principles in the Hatano-Nelson model with periodic boundary conditions and the non-Hermitian Su-Schrieffer-Heeger model.
  arXiv  Detail & Related papers  (2025-04-11T14:06:05Z)
• Observation of non-Hermitian bulk-boundary correspondence in non-chiral non-unitary quantum dynamics of single photons [31.05848822220465]
  In non-Hermitian systems, preserved chiral symmetry is one of the key ingredients, which plays a pivotal role in determining non-Hermitian topology.<n>We theoretically predict and experimentally demonstrate the bulk-boundary correspondence of a one-dimensional (1D) non-Hermitian system with chiral symmetry breaking.
  arXiv  Detail & Related papers  (2025-04-07T09:43:43Z)
• Symmetric observations without symmetric causal explanations [39.11025912171117]
  Inferring causal models from observed correlations is a challenging task, crucial to many areas of science.<n>In order to alleviate the effort, it is important to know whether symmetries in the observations correspond to symmetries in the underlying realization.
  arXiv  Detail & Related papers  (2025-02-20T19:00:00Z)
• Cooperative non-reciprocal emission and quantum sensing of symmetry breaking [4.431087385310259]
  Non-reciprocal propagation of energy and information is fundamental to a wide range of quantum technology applications. We show that interplay between anti-symmetric (symmetric) coherent and symmetric (anti-symmetric) dissipative interactions results in non-reciprocal couplings. We pave the way for realizing cooperative non-reciprocal transport in qubit ensembles without requiring time-modulated external drives or complex engineering.
  arXiv  Detail & Related papers  (2024-10-18T20:18:11Z)
• Scale-free localization and PT symmetry breaking from local non-Hermiticity [7.414433047076195]
  We show that a local non-Hermitian perturbation in a Hermitian lattice system generically induces scale-free localization for the continuous-spectrum eigenstates. Our results uncover a series of unexpected generic phenomena induced by a local non-Hermitian perturbation.
  arXiv  Detail & Related papers  (2023-02-08T18:43:51Z)
• Nonequilibrium symmetry-protected topological order: emergence of semilocal Gibbs ensembles [0.0]
  We consider nonequilibrium time evolution in quantum spin chains after a global quench. Because of them, the stationary state emerging at infinite time can exhibit exceptional features. Among the exceptional properties, we find that, at late times, the excess of entropy of a spin block triggered by a local perturbation in the initial state grows logarithmically with the subsystem's length.
  arXiv  Detail & Related papers  (2022-05-04T17:55:10Z)

This list is automatically generated from the titles and abstracts of the papers in this site.

This site does not guarantee the quality of this site (including all information) and is not responsible for any consequences.