In other words, not at all. According to criminology research I read about, and no I am not going to try and find this, the thing that deters is high probability of getting caught. That's why a robber is unlikely to rob a store if there is a cop there.
So if we actually wanted to reduce crime we would put money into detective work, and drastically reduce sentences overall so there would be room to put all those additional people who would get caught. We would also need drastically increased surveillance but we would have to live with that as the price of reducing crime. Plus deal with the problem of false conviction, which would be the toughest nut to crack.
Severe sentences do not deter crime. They are retributive, which humans find satisfying. Unfortunately that is how we are built, and it takes an effort of will to overcome that.
The thing that actually prevents rampant crime is that most people aren't criminals. If I'm out of cheese, I don't go and rob Trader Joe's because my self-definition is that I'm an honest person. Most people are similarly honest. Otherwise we would be in real trouble.