الفهرس 
Literature ReviewOnly 14 pages are availabe for public view
Abstract
Secured communication networks are the backbone for most of our daily applications, for example, electronic commerce banking, bill payments and remote healthcare monitoring. Therefore, the field of information technology has gained an increasing demand of security against any attacks either in storing the data, or while sending it. This can be achieved through cryptography principles, where the plain text is converted to ciphered text. Mainly, there are two classifications of cryptography: classical which depends on mathematical algorithms and quantum cryptography which depends on applying the laws of quantum mechanics. This thesis aims to introduce a full demonstration for the design and simulation for quantum secured direct communication system.
Firstly, an overview about different types of classical cryptography is listed where public and private key techniques are discussed. Then, quantum cryptography and its main features and advantages are presented briefly. Also, a historical brief about quantum secured direct communication systems is introduced and more advanced quantum systems are discussed where hyperentanglement is implemented to improve the efficiency and increase the capacity of such quantum systems.
This is followed by investigating the concept of spontaneous parametric down conversion and its different types. Then, quantum entanglement is described and how it can be physically realized. This leads to introducing an implementation of an EPR (Einstein–Podolsky–Rosen) source which is considered the source of quantum entangled photon pairs. Also, a simple experimental demo for EPR source is presented.
Data encoding is demonstrated where the entangled pairs of photons are regarded as data carriers, then an experimental methodology is illustrated for encoding process using optical components. Also, a security test is applied to detect any eavesdropping attack. This is achieved based on Bell’s inequality test. After that, timing synchronization between the data from the two parties is illustrated through coincidence counting mechanism.
Next, data decoding is investigated, where it depends on Bell state measurements and how discriminates different Bell states experimentally. Also, the effect of mismatch between data paths is analyzed.
Finally, some improvements are applied to quantum secured direct communication system to enhance its performance and increase the system capacity. This achieved by applying hyperentanglement principle where more degrees of freedom are deployed depending on physical quantities like polarization, energy-time, and momentum-position.
Keywords:
Quantum Cryptography, Entanglement, Quantum Secure Direct Communication, Bell state measurements, Bell’s inequality test, Hyperentangled, transverse momentum.