This thesis describes the deployment of a free-space quantum key
distribution system across the University of Waterloo campus. The
quantum key distribution system has the ability to provide
unconditionally secure communication between two parties: Alice and
Bob. The system exploits the quantum mechanical property of
entanglement in order to generate a key. Security is then guaranteed
by the No-Cloning theorem and the laws of quantum mechanics which
prevent a quantum system from being measured without disturbing it.
Polarization-entangled photon pairs are created using the non-linear
optical process of type-II spontaneous parametric down-conversion. A
free-space link of approximately $\mathrm{580~m}$ is used to
distribute one-half of the pairs to Alice at a distant location,
while the other half of the pairs are locally detected by Bob. The
details of the detection apparatus necessary to measure the
polarization of the photons and the software used to process the
measurement data according to the BBM92 protocol are described. An
experimental violation of the CHSH inequality (a derivative of the
original Bell inequality) is demonstrated to show that
polarization-entangled photon pairs are in fact being distributed to
the two parties. Finally, the full BBM92 protocol is performed using
the entangled photon pairs to generate a secure key and transmit an
encrypted message between Alice and Bob. Currently, the system can
only be operated at night because background light saturates the
detectors during the day; however, future work will focus on making
daylight operation feasible.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OWTU.10012/3021 |
| Date | 25 April 2007 |
| Creators | Erven, Chris |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Thesis or Dissertation |
| Format | 3928287 bytes, application/pdf |
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