On The Observables Analysis Of BB84 Photonic Encodings

Abstract

Information and communication theory studies and seeks justification to cause and effect of information creation, transformation and detection processes. Quantum Information Theory studies information and communication theory from the elementary particles known as of today using the quantum mechanics theory formalism. Akin to Shannon's entropy which quantifies information is a probabilistic measure in classical information theory, the Von Neumann entropy is defined as information in QIT. Over the years many new application have been developed from QIT awareness and QKD is perhaps the earliest and most matured application. BB84 protocol is earliest QKD protocol which allows two parties to exchange secret key for secure communication. QKD BB84 protocol has gained growing interest primarily because everyday today we exchange valuable information. The security of communication relies on the fact of impossibility of creating exact copies of quantum states and measuring the quantum state without destroying it. The key is encoded in the states of photons and transmitted over the noisy channel. Many different kinds of researches have been conducted to check the security of the protocol. The security of BB84 QKD protocol relies on QBER. It is desirable to posses QBER as a function of single observable. This thesis investigates polarization and phase shift encoding of BB84 protocol to answer the possibility of existence of such single observable. A photon source is assumed that emits single photons which are encoded in polarization and phase. A noisy channel acts on the encoded photons and are subsequently decoded. QBER is calculated for both encoding and results are compared to extract possible common observable that links to single observable.