The Quantum Ad Blocker is a browser extension which supposedly will block ads as well as third party trackers. It has been found by security experts, however, as an adware that will display unwanted and intrusive ads on your computer. These advertisements are in the form of shady coupons, push notifications, fake software updates, pop-up ads or banners, tech support scams and the likes. Clicking any of this ads will send you to malicious websites to get money from you or infect your computer further. It may also prevent you from changing your settings back.
Quantum Ad Blocker is usually installed through bundled software without you knowing.