Rihab Chatta

Full vector modal analysis of microstructured optical fiber propagation characteristics

Microstructured optical fibers (MOFs) are optical fibers having a periodic air-silica cross-section. The air holes extend along the axis of the fiber for its entire length. The core of the fiber is formed by a missing hole in the periodic structure. Remarkable properties of MOFs have recently been reported. This paper presents new work in the modeling of the propagation characteristics of MOFs using the Finite Element Method (FEM) and the Galerkin Method (GM). This efficient electromagnetic simulation package provides a vectorial description of the electromagnetic fields and of the associated effective index. This information includes accurate determination of the spectral extent of the modes, cutoff properties and mode-field distributions. We show that FEM is well adapted for describing the fields at abrupt transitions of the refractive index while GM has the advantage to accurately analyze MOFs of significant complexity using only modest computational resources. This presentation will focus on the specific techniques required to determine single mode operation, dispersion properties and effective area through careful choice of the geometrical parameters of the fibers. We demonstrate that with suitable geometrical parameters, the zero dispersion wavelength can be shifted. This tool can also provide design criteria for fabricating MOFs and a corresponding map of effective area. This approach is validated by comparison with experimental results and measurements on actual MOFs fabricated at IRCOM and at Alcatel Research and Innovation Center.

Spontaneous emission based on 2D photonic crystal and quantum dot

Spontaneous emission of light in semiconductor LEDs produces light that lack fixed-phase dependence; it is a question of incoherent light. However, it was proved that spontaneous emission depends not only on intrinsic property of material but also on the surrounding environment. Association between Quantum Dots (QD) and Photonic Crystals (CP) can have this role and modify characteristics of spontaneous emission and obtain wished results. In this paper we present another way to produce spontaneous emission with new interesting performances to arrive in produce a single photon source which produce indiscernible unique photons. Such sources are useful in quantum cryptography and quantum computing.

Non-deterministic quantum CNOT gate with double encoding

We define an Asymmetric Partially Polarizing Beam Splitter (APPBS) to be a linear optical component having different reflectivity (transmittance) coefficients, on the upper and the lower arms, for horizontally and vertically Polarized incident photons. Our CNOT model is composed by two APPBSs, one Half Wave Plate (HWP), two Polarizing Beam Splitters (PBSs), a Beam Splitter (BS) and a -phase rotator for specific wavelength. Control qubit operates with dual rail encoding while target qubit is based on polarization encoding. To perform CNOT operation in 4/27 of the cases, input and target incoming photons are injected with different wavelengths.

REALIZABILITY ASSESSMENT OF PROBABILISTIC QUANTUM CNOT GATE BASED ON EXPERIMENTAL IMPLEMENTATION

Generalized behavior of a nondeterministic CNOT gate based on physical implementation is subject of this work. We define an abstract probabilistic model of the CNOT gate and describe a general proposition of realizability assessment based on experimental features. Theoretical results are directly confronted to experimental realization. Two CNOT models are brought out for this purpose.

Photon pair generation 1310 – 1550 nm based on active photonic crystal: Heralded single photon source model

We report a heralded single photon source model; it consists on active two-dimensional crystal over LiNbO3 excited by a laser source at (1310 nm and 1550 nm). Photons detected through the crystal are filtered to eliminate of the laser source one. The photons at 1310 nm and 1550 nm will be spatially separated; the photon at 1310 nm is the trigger to announce the photon at 1550 nm. The contribution of this work is the using of the 2D photonic crystal to improve the conversion light efficiency and obtain height DOM at 1310 nm and 1550 nm, which will increase the probability to obtain single photon. This study can serve for the conception of new quantum communications protocols.

A quantum dot model for single photon source

Quantum key distribution protocol and quantum computing systems are based on single photon sources. A quantum dot (QD) and photonic crystal microcavity association can be a solution to obtain an efficient single photon sources. In this paper we present a quantum dot model with optimum geometrical parameters and materials to obtain a single photon emission at 1550 nm.

Behaviour of propagation through one dimension photonic crystal

In this work we present a first result of a 1D-photonic crystals (PC) modelling. Our final aim is the characterization of a multimode waveguide which uses this kind of crystal. In this case the optical propagation properties are strongly modified by the anisotropy of the photonic crystal. The transmission of a plane wave depends on the wavelength and its direction. Also the geometries of the structure must be taken into account. The results are obtained by using numerical tools: finite difference time domain (FDTD) and plane wave method (PWM).

Optimized QKD BB84 protocol using quantum dense coding and CNOT gates: feasibility based on probabilistic optical devices

In this work, we simulate a fiber-based Quantum Key Distribution Protocol (QKDP) BB84 working at the telecoms wavelength 1550 nm with taking into consideration an optimized attack strategy. We consider in our work a quantum channel composed by probabilistic Single Photon Source (SPS), single mode optical Fiber and quantum detector with high efficiency. We show the advantages of using the Quantum Dots (QD) embedded in micro-cavity compared to the Heralded Single Photon Sources (HSPS). Second, we show that Eve is always getting some information depending on the mean photon number per pulse of the used SPS and therefore, we propose an optimized version of the QKDP BB84 based on Quantum Dense Coding (QDC) that could be implemented by quantum CNOT gates. We evaluate the success probability of implementing the optimized QKDP BB84 when using nowadays probabilistic quantum optical devices for circuit realization. We use for our modeling an abstract probabilistic model of a CNOT gate based on linear optical components and having a success probability of sqrt (4/27), we take into consideration the best SPSs realizations, namely the QD and the HSPS, generating a single photon per pulse with a success probability of 0.73 and 0.37, respectively. We show that the protocol is totally secure against attacks but could be correctly implemented only with a success probability of few percent.

CNOT-based design and query management in quantum relational databases

In this work, we propose a complete design of a quantum relational multi-tables database. We illustrate how to perform basic and advanced queries to insert, update, delete and select records from single or joined digitized tables. A suggestion of a Quantum Query Language (QQL) is then addressed and we illustrate for a simple quantum database how QQL performs. We highlight the used scheme allowing to traduce the QQL semantics to the corresponding CNOT-based implementation and we underline the evolution of the amplitude of probability of the superposed states contained in the tables.

Optimized methods for inserting and deleting records and data retrieving in quantum database

In this paper, we show how a quantum CNOT-based relational database is built, then we show how to query its quantum tables using the most used SQL-like queries, e.g. INSERT, UPDATE, DELETE and SELECT. We specify each time the evolution of the probability amplitude corresponding to the records before and after the query has been executed and we propose corresponding circuits implementation.