Problems with detecting display using Belkin HDMI to MiniDP cable

I own a 2013 Macbook Pro and an iMac. I'm trying to use the iMac as my external display. Purchased a Belkin HDMI to MiniDP CABLE (not adapter) and plugged the HDMI end directly into my Macbook Pro (which supports HDMI), and the MiniDP end into my iMac. Neither computer is detecting the other as a display. Any explanation?

Can I not use the HDMI from my Macbook Pro to MiniDP on the external display I intend to use?

Thanks for the help!

- J.P.