That's a great and very practical question for city living. In a high-theft area, the goal isn't just to lock the bin, but to make stealing its contents or the bin itself more trouble than it's worth. The single most secure type of lock is a combination of two things: a heavy-duty, shrouded steel hasp and a high-security padlock.
Forget small cable locks or flimsy latches. You need a heavy-duty steel hasp (like those used on shipping containers or toolboxes) that is through-bolted to both the bin and its lid. This prevents someone from simply prying the lid open. Pair this with a reputable high-security padlock. Look for features like a shrouded or recessed shackle (which protects against bolt cutters), a disc-detainer or dual-ball-bearing core (resistant to picking), and a hardened steel body. Brands like Abus Granit or American Lock series 700 are excellent choices.
For bins with compatible handles, an integrated cylinder lock can be very effective, as it presents no exposed shackle to attack. In extreme cases, a heavy chain threaded through the bin's handles and anchored to a fixed point (like a post), secured with the same quality padlock, adds another layer of deterrence.
The principle is layered deterrence. You want a setup that resists prying, cutting, picking, and smashing. While no lock is 100% theft-proof, this combination significantly raises the effort and time required, encouraging thieves to move on to an easier target. Always ensure your locking method still allows authorized waste collection if needed.