Quantum-Dot Cellular Automata (QCA) is a radical nanotechnology, which works at Nanoscale. In this paper, an optimal design of 2n:1 Multiplexer (MUX) and 1:2n Demultiplexer (DeMUX) is presented. A new approach has been devised to implement efficient digital logic gates using the proposed 2n:1 multiplexer. To verify the functionality of the proposed structures some Boolean proofs are performed. A detailed comparison, structural evaluation and power analysis of the proposed multiplexer with recently robust designs are analyzed. This evaluates the performance of the proposed multiplexer in terms of cell count, area clock delays and energy dissipation as compared to traditional approaches. At temperature T = 2k, the energy dissipation is evaluated under the three separate tunneling energy levels (γ=0.5Ek,γ=1.0,Ek andγ=1.5Ek). New implementation and simulation results of the proposed 4n:1MUX and 1:4n DeMUX are developed using the proposed 2:1 MUX and 1:2 DeMux respectively. In addition, a novel concept of QCA based Multiplexing/Demultiplexing is presented. This paves way sharing a single communication link among the number of devices at nano-regime.