Various embodiments of the present invention are directed to nanowire crossbars that use configurable, tunneling resistor junctions to electronically implement logic gates. In one embodiment of the present invention, a nanowire crossbar comprises two or more layers of approximately parallel nanowires, and a number of configurable, tunneling resistor junctions that each interconnects a nanowire in a first layer of approximately parallel nanowires with a nanowire in a second layer of approximately parallel nanowires.