hmmm, i'm not all that sure about 1-wire mode. i'm using the chip as it comes out of the box: in 4-wire SPI slave mode. to set it to 1-wire mode i think you need a special cloning adapter (QTM300CA) to change the relevant parameter. from memory, i think it will cost more than an arduino... here's the user's guide:
http://www.qprox.com/downloads/manuals/qtm300ca_102.pdf
but you'd better chack that it's what you need before forking out the cash. also, if you just want to run several QT300s with one arduino, there's a section in the QT300 datasheet that explains how to use several chips over a single SPI interface. i think you need 3 common wires, then one wire for each chip...?
j.