All quantum-mechanical processes can be reversed. In fact, this process is actually a lot more common in the other direction; a positron and an electron making

All quantum-mechanical processes can be reversed. In fact, this process is actually a lot more common in the other direction; a positron and an electron making a pair of photons is matter-antimatter annihilation and it happens all the time. This is because a couple photons are thermodynamically preferred over an electron-positron pair at room temperature. It's kind of like how allotropes of solids will form and reform as you change the heat and pressure.