Downloading QCircuit 1.0 for Mac from the developer's website was possible when we last checked. We cannot confirm if there is a free download of this app available. We recommend checking the downloaded files with any free antivirus. QCircuit for Mac lies within Education Tools, more precisely Science. This free Mac application is an intellectual property of Matthew Ewer.
From the developer:
QCircuit is an aid for understanding, designing, and simulating quantum circuits. You essentially drag and drop gates into place on a set of "wires" and see its effects. You can feed input bits in one end of a circuit and watch the values change as they continue through the circuit.
You may want to check out more software for Mac, such as sciatrope, Analytics to Earth or TreeView X, which might be related to QCircuit.