Trajectories of Critical Unstable Qubits in and on the Bloch Sphere

• URL: http://arxiv.org/abs/2606.01405v1
• Date: Sun, 31 May 2026 19:04:43 GMT
• Title: Trajectories of Critical Unstable Qubits in and on the Bloch Sphere
• Abstract summary: We extend previous studies on a class of unstable two-level systems called Critical Unstable Qubits (CUQs)<n>The CUQs exhibit striking phenomena of indefinite anharmonic oscillations between two states and coherence-decoherence oscillations of mixed states.<n>The potential implications of our findings for particle cosmology and quantum simulations of non-Hermitian Hamiltonians are discussed.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: We extend previous studies on a novel class of unstable two-level systems which were called Critical Unstable Qubits (CUQs). In an appropriately defined co-decaying frame, the CUQs exhibit striking phenomena of indefinite anharmonic oscillations between two states and coherence-decoherence oscillations of mixed states. These features are distinct from the usual Rabi oscillations observed in the Hermitian counterpart of two-level systems, which are harmonic and preserve the coherence of the quantum state. We employ the density matrix formalism to study these phenomena for mixed states and delve into the nature of the trajectory traversed by these states in the Bloch sphere by studying the time evolution of the Bloch vector that describes the quantum state of the unstable qubit. In particular, we provide for the first time explicit geometric constructions to obtain trajectories of both pure and mixed CUQs in and on the Bloch sphere. This enables us to identify the stationary points of CUQs, at which the states do not evolve in time in the co-decaying frame. The potential implications of our findings for particle cosmology and quantum simulations of non-Hermitian Hamiltonians are discussed.

Related papers

• Entanglement-facilitated macroscopic cluster formation in quantum many-body dynamics [42.89492957665636]
  We find that initial-state entanglement suppresses the proliferation of true-vacuum bubbles and stabilises macroscopic connected clusters.<n>Our results establish a connection between initial-state preparation and the preservation of global structures.
  arXiv  Detail & Related papers  (2026-05-21T18:21:14Z)
• Hysteretic squashed entanglement in many-body quantum systems [42.085941481155295]
  Entanglement in many-body quantum systems is distributed across spatial regions.<n>We propose hysteretic entanglement $T_sq$, a conditional entanglement that measures the genuine quantum correlations between two subregions.<n>We show that $T_sq$ can detect genuine quantum correlations across both adjacent and long-range subsystems.
  arXiv  Detail & Related papers  (2026-03-10T17:00:49Z)
• Emergence of cosmic structure from Planckian discreteness [47.03992469282679]
  In the standard paradigm the inhomogeneities observed in the CMB arise from quantum fluctuations of an initially homogeneous and isotropic vacuum state.<n>We propose an alternative paradigm in which such inhomogeneities are present from the very beginning.<n>Specifically, inhomogeneities in the quantum state at the Planck scale propagate into semiclassical inhomogeneities on CMB scales.
  arXiv  Detail & Related papers  (2025-06-18T12:33:31Z)
• Theory of the correlated quantum Zeno effect in a monitored qubit dimer [41.94295877935867]
  We show how the competition between two measurement processes give rise to two distinct Quantum Zeno (QZ) regimes.<n>We develop a theory based on a Gutzwiller ansatz for the wavefunction that is able to capture the structure of the Hilbert phase diagram.<n>We show how the two QZ regimes are intimately connected to the topology of the flow of the underlying non-Hermitian Hamiltonian governing the no-click evolution.
  arXiv  Detail & Related papers  (2025-03-28T19:44:48Z)
• Quantum-classical correspondence of non-Hermitian spin-orbit coupled bosonic junction [4.934387267206206]
  We show that near the symmetry-breaking phase transition point, the correspondence between classical (mean-field) and quantum dynamics is more likely to break down. In both the mean-field and many-particle models, the SOC effects can greatly promote the synchronous periodic oscillations between the spin-up and spin-down components.
  arXiv  Detail & Related papers  (2024-10-17T02:58:17Z)
• Edge modes and symmetry-protected topological states in open quantum systems [0.0]
  Topological order offers possibilities for processing quantum information which can be immune to imperfections.<n>We utilize this robustness against a wide class of dissipation channels in the Lindblad and quantum formalisms of an open quantum system.<n>Our work thus proposes a novel framework to study the dynamics of dissipative SPT phases and opens the possibility of engineering entangled states relevant to quantum information processing.
  arXiv  Detail & Related papers  (2023-10-13T21:09:52Z)
• Intrinsic Mixed-state Topological Order [4.41737598556146]
  We show that decoherence can give rise to new types of topological order.<n>We construct concrete examples by proliferating fermionic anyons in the toric code via local quantum channels.<n>The resulting mixed states retain long-range entanglement, which manifests in the nonzero topological entanglement negativity.
  arXiv  Detail & Related papers  (2023-07-25T18:34:10Z)
• Hilbert Space Fragmentation in Open Quantum Systems [0.7412445894287709]
  We investigate the phenomenon of Hilbert space fragmentation (HSF) in open quantum systems. We find that it can stabilize highly entangled steady states.
  arXiv  Detail & Related papers  (2023-05-05T18:00:06Z)
• Measurement phase transitions in the no-click limit as quantum phase transitions of a non-hermitean vacuum [77.34726150561087]
  We study phase transitions occurring in the stationary state of the dynamics of integrable many-body non-Hermitian Hamiltonians. We observe that the entanglement phase transitions occurring in the stationary state have the same nature as that occurring in the vacuum of the non-hermitian Hamiltonian.
  arXiv  Detail & Related papers  (2023-01-18T09:26:02Z)
• Gauge-theoretic origin of Rydberg quantum spin liquids [0.0]
  We introduce an exact relation between an Ising-Higgs lattice gauge theory on the kagome lattice and blockaded models on Ruby lattices. This relation elucidates the origin of previously observed topological spin liquids by directly linking the latter to a deconfined phase of a solvable gauge theory.
  arXiv  Detail & Related papers  (2022-05-25T18:19:26Z)
• Quantum particle across Grushin singularity [77.34726150561087]
  We study the phenomenon of transmission across the singularity that separates the two half-cylinders. All the local realisations of the free (Laplace-Beltrami) quantum Hamiltonian are examined as non-equivalent protocols of transmission/reflection. This allows to comprehend the distinguished status of the so-called bridging' transmission protocol previously identified in the literature.
  arXiv  Detail & Related papers  (2020-11-27T12:53:23Z)
• Unraveling the topology of dissipative quantum systems [58.720142291102135]
  We discuss topology in dissipative quantum systems from the perspective of quantum trajectories. We show for a broad family of translation-invariant collapse models that the set of dark state-inducing Hamiltonians imposes a nontrivial topological structure on the space of Hamiltonians.
  arXiv  Detail & Related papers  (2020-07-12T11:26:02Z)

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.