Unmeasurement of the state of a quantum particle reverts it to its original unlocalized state.
Most scientists have believed that the instant a quantum object was measured it would collapse from being in all the locations it could be, to just one location like a classical object.
Recent experiments showed that it is possible to weakly measure the particle continuously, partially collapsing the quantum state, and then unmeasure it, causing the particle to revert back to its original quantum form, before it collapsed.
Since 1926, theorists believed that measurement of a quantum particle inevitably forced a collapse, it was understood that measurements created reality as we understand it.
Being able to reverse the collapse means that we can't assume measurements create reality because it is possible to erase the effects of a measurement and start again.
If reality can be uncreated or erased, the concept of determinism is undermined. The future is therefore fundamentally nonexistent until it comes into being.