{
  "annotation_id": "60efbffd-aafd-4bc0-bf8a-6dc28f93989f",
  "date_created": "2026-03-02T18:02:27.284000Z",
  "date_modified": "2026-03-02T18:02:27.284000Z",
  "file_hash": "86a42650238e3687ab4a6a32f9ae177b13b7e49ebbf46344c5079bf8ce9a259a",
  "private": false,
  "record": {
    "abstract": "We present a design for a quantum key distribution(QKD) system in a Sagnac\nloop configuration, employing a novel phase modulation scheme based on\nfrequency shift, and demonstrate stable BB84 QKD operation with high\ninterference visibility and low quantum bit error rate (QBER). The phase\nmodulation is achieved by sending two light pulses with a fixed time delay (or\na fixed optical path delay) through a frequency shift element and by modulating\nthe amount of frequency shift. The relative phase between two light pulses upon\nleaving the frequency-shift element is determined by both the time delay (or\nthe optical path delay) and the frequency shift, and can therefore be\ncontrolled by varying the amount of frequency shift. To demonstrate its\noperation, we used an acousto-optic modulator (AOM) as the frequency-shift\nelement, and vary the driving frequency of the AOM to encode phase\ninformation.The interference visibility for a 40km and a 10km fiber loop is 96%\nand 99%, respectively, at single photon level. We ran BB84 protocol in a 40-km\nSagnac loop setup continuously for one hour and the measured QBER remained\nwithin the 2%~5% range. A further advantage of our scheme is that both phase\nand amplitude modulation can be achieved simultaneously by frequency and\namplitude modulation of the AOM\u0027s driving signal, allowing our QKD system the\ncapability of implementing other protocols, such as the decoy-state QKD and the\ncontinuous- variable QKD. We also briefly discuss a new type of Eavesdropping\nstrategy (\"phaseremapping\" attack) in bidirectional QKD system.",
    "arxiv_id": "quant-ph/0604187",
    "authors": [
      "Bing Qi",
      "Lei-Lei Huang",
      "Hoi-Kwong Lo",
      "Li Qian"
    ],
    "categories": [
      "quant-ph"
    ],
    "doi": "10.1364/OE.14.004264",
    "journal_ref": "Optics Express Vol. 14 p4264-4269 (2006)",
    "title": "Quantum key distribution based on a Sagnac loop interferometer and   polarization-insensitive phase modulators",
    "url": "https://arxiv.org/abs/quant-ph/0604187"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "3c554a5f-3edf-4d9f-be0e-fc9b3c177ed9",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}