Ahh so the ground acts as electrical ground AND a reference point for the signal?
So I would only need the 5v pin of the IR Receiver connected to one of them, but ground and signal would need to be connected to both of them.
Think of how you would measure the signal with a meter. You can't just jab the red lead onto the signal output: you have to jab the black one in on the 0 too
But heed what drksam said too: the signal's voltage
will be made available to both devices but I'm not 100% sure if there would be any significant current
required from the sensor which I guess could fall short on that.... YMMV.