1 Introduction 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42] as well as experimentally [13, 14, 15, 16, 17, 18, 19], yet lot of controversies are still present between the theory and experiment, and the complete descrip- tion of the conduction mechanism in this scale is not very well defined even today. Several control- ling factors are there which can significantly regu- late electron transport in a conducting bridge, and all these factors have to be taken into account prop- erly to understand the transport mechanism. For our illustrative purposes, here we mention some of these issues. The study of electronic transport in quantum con- fined model systems like quantum rings, quantum dots, arrays of quantum dots, quantum dots em- bedded in a quantum ring, etc., has become one of the most fascinating branch of nanoscience and technology. With the aid of present nanotechnolog- ical progress [1, 2], these simple looking quantum confined systems can be used to design nanodevices especially in electronic as well as spintronic engi- neering. The key idea of manufacturing nanode- vices is based on the concept of quantum interfer- ence effect [3, 4, 5], and it is generally preserved throughout the sample having dimension smaller or comparable to the phase coherence length. There- fore, ring type conductors or two path devices are ideal candidates to exploit the effect of quantum in- terference [6]. In a ring shaped geometry, quantum interference effect can be controlled by several ways, and most probably, the effect can be regulated sig- nificantly by tuning the magnetic flux, the so-called Aharonov-Bohm (AB) flux [7, 8, 9, 10], that threads the ring. This key feature motivates us to widely use quantum interference devices in mesoscopic solid-state electronic circuits [11]. Using a meso- scopic ring we can construct a quantum interferom- eter, and here we will show that the interferometer exhibits several exotic features of electron trans- port which can be utilized in designing nanoelec- tronic circuits. To reveal the phenomena, we make a bridge system, by inserting the interferometer be- tween two electrodes (source and drain), the so- called source-interferometer-drain bridge. Follow- ing the pioneering work of Aviram and Ratner [12], theoretical description of electron transport in a bridge system has got much progress. Later, many excellent experiments [13, 14, 15, 16, 17, 18, 19] have been done in several bridge systems to un- derstand the basic mechanisms underlying the elec- tron transport. Though extensive studies on elec- tron transport have already been done both theo- retically [7, 8, 9, 10, 20, 21, 22, 23, 24, 25, 26, 27, 28, 1. The quantum interference effect [28, 29, 30, 31, 32, 33, 34] of electronic waves passing through different arms of the bridging material becomes the most significant issue. 2. The coupling of the bridging material to the electrodes significantly controls the current amplitude across any bridge system [32]. 3. Dynamical fluctuation in small-scale devices is another important factor which plays an ac- tive role and can be manifested through the measurement of shot noise [36], a direct conse- quence of the quantization of charge. 4. Geometry of the conducting material between the two electrodes itself is an important is- sue to control electron transmission which has been described quite elaborately by Ernzerhof et al. [42] through some model calculations. Addition to these, several other factors of the tight-binding Hamiltonian that describe a system also provide important effects in the determination of current across a bridge system. In this presentation we explore electron trans- port properties of a quantum interferometer based on the single particle Green’s function formalism. The interferometer is sandwiched between two semi- infinite one-dimensional (1D) metallic electrodes, viz, source and drain, and, two sub-rings of the interferometer are subject to the Aharonov-Bohm 2