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Source: https://writers.stackexchange.com/a/41390
License name: CC BY-SA 3.0
License URL: https://creativecommons.org/licenses/by-sa/3.0/

Source: https://writers.stackexchange.com/a/41390
License name: CC BY-SA 3.0
License URL: https://creativecommons.org/licenses/by-sa/3.0/

You have another problem, if you solve that, you solve this.

### How did we figure out it was quantum computer activity that signaled them?

If this is told omnisciently or from the alien POV, you have no problem:

> Alien #1: "A sustained trans-universe anomaly in sector 37. Quantum computing detected. Exceeding 100 qubits in total."
> 
> Alien #2: "Verified. I've scheduled an extermination bot. I have a transfer reservation on portal seven, it should open in [thirty minutes]."

If it is told from a human point of view, they either won't know why it happened now, or you arrange the plot so they find out.

The smart quantum physicist that figures it out (say he is on vacation in the wilderness when it happens) is bothered by what caused it for some time in the book.

He finally learns that the device that released the biological agent arrived at time X:Y, less than one hour after the minute this massive quantum computer was turned on for its first test run, a project that had taken three years and billions of dollars to complete.

Heck, maybe he even finds the expended drone they sent; no reason for the aliens to retrieve it; and in analyzing it figures out it was a quantum computing device too, but centuries ahead of anything humans could have done. Thus alien. And his own theories of quantum physics and alien life finish the conjecture.

Original score: 15