Decoy state quantum key distribution

Experimental weak + vacuum protocol has been demonstrated using commercial QKD system based on a standard bi-directional ‘Plug & Play’ set-up. By making simple modifications to a commercial quantum key distribution system, decoy state QKD allows us to achieve much better performance than QKD system without decoy state in terms of key generation rate and distance. We demonstrate an unconditionally secure key rate of 6.2931 x 10-4 per pulse for a 25 km fiber length

A single photon quantum user bi-directional authentication scheme over noiseless channel

In this paper, we propose a quantum user authentication protocol with single photon based on short shared secret key and quantum bit error ratio verification. In this scheme, usage of proposed deterministic quantum key distribution technique and simple verification in a public channel culminate reduced photon transmission. Security analysis proves our proposed scheme is resistant to impostors' attacks and eavesdropper. Furthermore, our proposed protocol can extend to multiparty environment and permits to re-use many times of the shared secret key without revealing it

An efficient modeling and simulation of quantum key distribution protocols using OptiSystem™

In this paper, we propose a modeling and simulation framework for quantum key distribution protocols using commercial photonic simulator OptiSystem™. This simulation framework emphasize on experimental components of quantum key distribution. We simulate BB84 operation with several security attacks scenario and noise immune key distribution in this work. We also investigate the efficiency of simulator's inbuilt photonic components in terms of experimental configuration. This simulation provides a study to analyze the impact of experimental photonic components in quantum key distribution process

Development and Characterization of Multi-Wavelength Fiber Laser Light Sources Based on Erbium and Brillouin Gain

This thesis presents the research works that has been carried out in the development and characterizations of light sources based on two gain medium, namely Erbium and Brillouin. The laser gain medium used in the research work is in the form of optical fiber rather than bulk piece of doped crystal or glass. The physical structure of the gain medium makes it easy to be spliced with other optical components in the Fiber laser configurations. The Brillouin gain comes from a standard single mode fiber used in the optical fiber communication system. The aim of the research work is to investigate various techniques in Fiber laser that allow the generation of multiple laser output (or multi-wavelength) from a single light source unit. The techniques differ from each other in the wavelength selection mechanism and the gain medium used in the configurations. In the first experiment, optical fiber Bragg grating has been chosen as the wavelength selective technique. Through this configuration, a dual and switchable laser output can be constructed. The output of the laser can be made to switch between single wavelength or with both wavelengths lases simultaneously. A moderate laser output power (about 10 mW at 60 mW EDF pump power) has also been achieved with both output power has a uniform power level. The multi-wavelength output can be easily increased through the addition of more optical fiber Bragg grating. Through a linear fiber laser configuration which incorporates Fabry-Perot band-pass filter, a dual laser output system has been demonstrated. A novel technique has been suggested which allows for a uniform output power levels at any wavelengths within the EDF allowable gain profile. This was achieved by varying the optical attenuator values placed at one of the laser cavity loops such that it changes the cavity loss at that particular wavelength of interest. Finally, by combining two gain medium within a laser cavity, a fiber laser system that is capable of achieving high number of laser outputs is being constructed. The mechanism that is responsible for the generation of the multiple laser output is the Stimulated Brillouin scattering phenomena and the feedback loop that is incorporated within the laser cavity. Output of more than 20 laser lines could be achieved with such configuration. Besides producing a high number of laser lines, the output can also be made tuneable within a wide range. A tuning range of up to 34 nm has been demonstrated for a ring laser configuration and 17 nm for linear laser configuration. The work presented in this thesis also reported for the first time a tuneable L-band Brillouin/Erbium fiber laser system adopting a linear laser cavity. A tuning range of up to11 nm can be achieved with average laser output of 10 signals

Optimization of EDF pump for efficient brillouin/ erbium fiber ring laser operation

We report here experimental results on the finding of an optimum Erbium pump power in obtaining a Brillouin-generated Stokes signal with the best quality. The quality of the Stokes signal is mainly characterized by its isolation from unwanted modes and noises. We also propose here a new parameter to characterize the signal further that is by using peak power-isolation product. With this particular system, we obtained an optimum Erbium pump power of 48.93 miliwatt producing a peak power 2.91 mW and isolation of 17.6 dB or a peak power-isolation product of 51.23 dB-dBm

A study of stoichiometric composition of Ge thermal oxide by X-ray photoelectron spectroscopic depth profiling

The evolution of different oxidation states during thermal oxidation of (100) oriented Ge substrate was investigated with X-ray photoelectron spectroscopic analysis. The thermally grown oxides in the temperature range of 380 to 500°C were found to consist of four different oxidation states of Ge, namely, Ge1+, Ge2+, Ge3+, and Ge4+. The fractional composition of the oxide species is seen to be dependent on oxidation temperature. Spectroscopic depth profiling reveals variation of oxide composition along the depth of the oxide layer with a large concentration of GeO2 near the oxide surface and a large concentration of suboxides near the oxide/Ge interface. The results obtained in the investigation will help in achieving greater insight into the thermal oxidation process of Ge

Characterization of four states polarization flipper for single photon application

We report characterization result using weak coherent pulses on four states polarization flipper utilizing two Pockels cells. Visibility of nearly 90 and above was achieved for each four linear polarization input states. A good polarization contrast between not flipped and flipped states shows that this configuration can be applied for single photon applications

Method and apparatus for optical polarization photon generator

A method and apparatus for optically generating polarized photons with at least four polarization states is disclosed. The method and apparatus comprises at least two laser sources that are electronically triggered at random to generate at least two optical pulses (102), an arrangement of passive optical components that polarize each optical pulse of the at least two optical pulses to have orthogonal polarization states (104) and merge the at least two optical pulses having orthogonal polarization states onto a single optical path (106) and an active optical component that alters the orthogonal polarization states of the single optical path to have secondary orthogonal polarization states (108)