{
  "annotation_id": "220ca252-5f32-4887-9ac8-ecc411c76af7",
  "date_created": "2026-03-02T18:02:27.590000Z",
  "date_modified": "2026-03-02T18:02:27.590000Z",
  "file_hash": "cf7a0063f8ae57b266d9af8ca1fab6a36b8483f02d7370644db8e9c1872bd4d4",
  "private": false,
  "record": {
    "abstract": "We have found that for a wide range of two-qubit Hamiltonians the\ncanonical-ensemble thermal state is entangled in two distinct temperature\nregions. In most cases the ground state is entangled; however we have also\nfound an example where the ground state is separable and there are still two\nregions. This demonstrates that the qualitative behavior of entanglement with\ntemperature can be much more complicated than might otherwise have been\nexpected; it is not simply determined by the entanglement of the ground state,\neven for the simple case of two qubits. Furthermore, we prove a finite bound on\nthe number of possible entangled regions for two qubits, thus showing that\narbitrarily many transitions from entanglement to separability are not\npossible. We also provide an elementary proof that the spectrum of the thermal\nstate at a lower temperature majorizes that at a higher temperature, for any\nHamiltonian, and use this result to show that only one entangled region is\npossible for the special case of Hamiltonians without magnetic fields.",
    "arxiv_id": "quant-ph/0605176",
    "authors": [
      "Dominic W. Berry",
      "Mark R. Dowling"
    ],
    "categories": [
      "quant-ph"
    ],
    "doi": "10.1103/PhysRevA.74.062301",
    "journal_ref": "Phys. Rev. A 74, 062301 (2006)",
    "title": "Two qubits can be entangled in two distinct temperature regions",
    "url": "https://arxiv.org/abs/quant-ph/0605176"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "96204c5f-7514-451e-bb64-7ec7161de947",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}