In this work we address a comparison study between two kinds of Single Photon Sources (SPS). The first SPS is an Enhanced SPS (ESPS), which consists of an association between InAs/GaAs Quantum Dot (QD) and photonic crystal (PC) microcavity. The ESPS emits a single photon at 1550 nm with probability P1 around 0.7. The second SPS is the Heralded SPS (HSPS) and based on active two-dimensional PC over LiNbO3 and emits photons at 1310 nm and 1550nm. The photon at 1310 nm triggers the detection mechanism of the photon at 1550nm. The probability to obtain a HSPS at 1550 nm is closed to 0.57. Finally, we present a comparison study between ESPS and HSPS when they are used in an application of quantum communication.
In this work, we study the error sources standing behind the non-perfect linear optical quantum components composing a non-deterministic quantum CNOT gate model, which performs the CNOT function with a success probability of 4/27 and uses a double encoding technique to represent photonic qubits at the control and the target. We generalize this model to an abstract probabilistic CNOT version and determine the realizability limits depending on a realistic range of the errors. Finally, we discuss physical constraints allowing the implementation of the Asymmetric Partially Polarizing Beam Splitter (APPBS), which is at the heart of correctly realizing the CNOT function.
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.
The work presented in this paper develops a new formalism to design microdisks and microgears structures. The main
objective is to study the optics and geometrics parameters influence on the microdisks and microgears structures
resonance behavior. This study is conducted to choice a resonance structure with height quality factor Q to be associated
with Quantum dot to form a single photon source. This new method aims to design resonant structures that are simpler
and requires less computing performances than FDTD and Floquet Block methods. This formalism is based on
simplifying Fourier transformed and using toeplitz matrix writing. This new writing allows designing all kind of
resonance structures with any defect and any modification. In other study we have design a quantum dot emitting a
photon at 1550 nm of the fundamental mode, but the quantum dot emits other photons at other wavelengths. The focus of
the resonant structure and the quantum dot association is the resonance of the photon at 1550 nm and the elimination of
all other photons with others energies. The quantum dot studied in [1] is an InAs/GaAs quantum dot, we design an GaAS
microdisk and microgear and we compare the quality factor Q of this two structures and we conclude that the microgear
is more appropriated to be associate to the quantum dot and increase the probability P1 to obtain a single photon source
at 1550 nm and promotes the obtaining of single photon. The performance improving of the resonant structure is able to
increase the success of quantum applications such as quantum gates based on single photon source.
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.
We analyse the coupling characteristics of dual-core photonic crystal fibre couplers by a 3D finite difference vector beam propagation method. Beam propagation analysis of photonic crystal fibre couplers is performed in terms of coupling length and coupling efficiency. The determination of the guiding properties such as the propagation constants is evaluated using a mode solver based on plane wave method. We study the influence of the photonic crystal fibre coupler geometrical parameters on the coupling length at different wavelengths. Variable size of the central hole is considered to improve the coupling between the two cores. It is shown that it is possible to design shorter photonic crystal fibre couplers with coupling lengths of hundred micrometers compared to conventional optical fibre couplers. We demonstrate that the designed coupler can operate as a polarization preserving directional coupler. This study confirms that this device can act as an efficient ultra small wavelength selective coupler.
We present experimental results on Microstructured Optical Fibre (MOF) coupling with standard Single Mode Fibre (SMF) using a simple and reliable set-up. An electric-arc splicing system is used to demonstrate its effectiveness in splicing SMF with MOFs. The measurements of the additional loss induced by transverse and longitudinal offsets at connections between SMF and MOF are reported and discussed. The influence of mode size mismatch is emphasized.
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.
The Beam Propagation Method (BPM) is the most widely used tool for the investigation of complex photonic structures. Since the original BPM was introduced, many improvements and extensions have been proposed. We have developed a computer program based on the Finite Difference BPM for modeling propagation in optical waveguides. This method has been successfully applied for several 3D problems such as propagation on Bragg Fiber. The main drawback of this method is its complexity and long computation time using a personal computer. In this paper, a simple efficient numerical solution method, we called double 2D-BPM, is proposed. This technique is based on the decomposition of the 3D field propagation equation onto two 2D equations related to transverse plans. Propagation along the x and y axes is computed separately in two steps. Using a similar technique, a finite difference approximation for each propagation step involves the solution of two equations and the complete problem splits into two independent 2D problems. We performed propagation tests in elementary 3D problems but also on Bragg fiber. The numerical results of 3D-BPM and double 2D-BPM have been compared. The propagation step along the propagation axis has been experimentally determined. Parameters that affect the accuracy and the stability of this method were discussed. Losses induced by propagation on Bragg fiber were also considered. We have established that the global effect of the double 2D-BPM is equivalent to 3D-BPM technique. Comparison with exact results obtained from analytical expressions also shows excellent agreement.
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