QCircuit is a tool for designing and (to a certain extent) testing quantum circuits. Not really intended for large circuits, but no restrictions have been implemented.

There are no hardcoded limits, but your computer may bo be able to handle more than a certain number of bits for some operations - specifically, Test Run and, even more so, matrix operations.

On the left there is the toolbox, full of tools and modes to select. On the bottom is the properties box, where it shows the properties of selected things. On the top right is the viewport. It shows you the circuit you're building. Click and dray to pan, scroll to zoom in and out, push spacebar to redrawm which also recalculates states if you're in Test Run mode.

Requirements:
* Java

The license of this software is Free, you can free download and free use this calculator software.