Tiny black holes are the kind of thing that physically cant exist for more than a few like picosecods or something ridiculous like that before evaporating into radio waves.
You have an app with a private key.
The qr code contains data encrypted with the corresponding public key. Your app decrypts the data and transmits it to googles servers, proving you are in possession of the secret key.
We eat like 2 plants. One is brassica mentioned above.
The other one is nightshade. In the nightshade family we find tomatos, aubergine, tobacco, peppers, physalis, potatoes and of course the extremely toxic bella-donna (deadly nightshade)
If the adversary has physical access you are generally pwned either way