filtering by IP address how?

the IP address of your modem? Well your ISP will easily be able to tell whether or not you're using a VPN. And I guess at that level if someone used a quantum computer on your modem's connection from the modem to the proxy, then yeah, they'd probably be able to evesdrop as long as they have access to the lines from your house to the hub of your local ISP and the VPN you're using doesn't have quantum-safe encryption.

If you're in a position where you'd need to worry about a corporation or government using a quantum computer to get into your shit you've got bigger problems.

From what I understand, it requires a fuck-ton of electricity to run a quantum PC and they'd need to use even more electricity on top of that to keep it cool in a refrigerated room at sub-zero temperatures.

But that's only what all the tech-companies making them are currently saying. There's probably more advanced stuff that they're keeping secret. We'll never know until another whistleblower sacrifices their entire life to tell the world about it.