dorsal/arxiv
View SchemaQuantum cryptography via parametric downconversion
| Authors | Gilles Brassard, Tal Mor, Barry C. Sanders |
|---|---|
| Categories | |
| ArXiv ID | quant-ph/9906074 |
| URL | https://arxiv.org/abs/quant-ph/9906074 |
| DOI | 10.1007/0-306-47097-7_51 |
Abstract
The use of quantum bits (qubits) in cryptography holds the promise of secure cryptographic quantum key distribution schemes. It is based usually on single-photon polarization states. Unfortunately, the implemented ``qubits'' in the usual weak pulse experiments are not true two-level systems, and quantum key distribution based on these imperfect qubits is totally insecure in the presence of high (realistic) loss rate. In this work, we investigate another potential implementation: qubits generated using a process of parametric downconversion. We find that, to first (two-photon) and second (four-photon) order in the parametric downconversion small parameter, this implementation of quantum key distribution is equivalent to the theoretical version. Once realistic measurements are taken into account, quantum key distribution based on parametric downconversion suffers also from sensitivity to extremely high (nonrealistic) losses. By choosing the small parameter of the process according to the loss rates, both implementations of quantum key distribution can in principle become secure against the attack studied in this paper. However, adjusting the small parameter to the required levels seems to be impractical in the weak pulse process. On the other hand, this can easily be done in the parametric downconversion process, making it a much more promising implementation.
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"abstract": "The use of quantum bits (qubits) in cryptography holds the promise of secure\ncryptographic quantum key distribution schemes. It is based usually on\nsingle-photon polarization states. Unfortunately, the implemented ``qubits\u0027\u0027 in\nthe usual weak pulse experiments are not true two-level systems, and quantum\nkey distribution based on these imperfect qubits is totally insecure in the\npresence of high (realistic) loss rate. In this work, we investigate another\npotential implementation: qubits generated using a process of parametric\ndownconversion. We find that, to first (two-photon) and second (four-photon)\norder in the parametric downconversion small parameter, this implementation of\nquantum key distribution is equivalent to the theoretical version.\n Once realistic measurements are taken into account, quantum key distribution\nbased on parametric downconversion suffers also from sensitivity to extremely\nhigh (nonrealistic) losses. By choosing the small parameter of the process\naccording to the loss rates, both implementations of quantum key distribution\ncan in principle become secure against the attack studied in this paper.\nHowever, adjusting the small parameter to the required levels seems to be\nimpractical in the weak pulse process. On the other hand, this can easily be\ndone in the parametric downconversion process, making it a much more promising\nimplementation.",
"arxiv_id": "quant-ph/9906074",
"authors": [
"Gilles Brassard",
"Tal Mor",
"Barry C. Sanders"
],
"categories": [
"quant-ph"
],
"doi": "10.1007/0-306-47097-7_51",
"title": "Quantum cryptography via parametric downconversion",
"url": "https://arxiv.org/abs/quant-ph/9906074"
},
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