Compact Interconnection Networks Based on Quantum Dots

NASA's Jet Propulsion Laboratory, Pasadena, California

Wednesday, January 01 2003 One especially useful interconnection network is an N × N crossbar network. A QCA circuit capable of a high-impedance output state would be needed to implement a crosspoint switch in a crossbar network. This is because while all N input lines cross a given output line, only one input line is allowed to put a signal on that output line; in other words, the connections between the other input lines and the given output line are required to be of high impedance in order to block signals.

Figure 2 depicts a proposed QCA-based crosspoint switch and a 3 × 3 crossbar network. The crosspoint switch would contain several branched QCA subarrays excited by suitably phased clock signals, and one of the quantum cellular automatons would serve as a control switch. The input signal I_i would propagate toward the output line along one branch and, by suitable clocking and coupling, would be converted to another signal, I_f, propagating toward the output line along another branch. The application of a "0" signal to the control switch would cause I_i and I_f to be of the same state (both 0 or both 1), thereby causing the signal I_i to be coupled onto the output line; in effect, the crosspoint switch would be in a low-impedance state. On the other hand, the application of a "1" signal to the control switch would cause I_f to be the opposite of I_i, thereby preventing coupling of either I_i or I_f onto the output line; in effect, the crosspoint switch would be in a high-impedance state.

This work was done by Amir Fijany, Nikzad Toomarian, Katayoon Modarress, and Matthew Spotnitz of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Computers/Electronics category.