As we all know elliptic curve cryptography is vulnerable to a quantum computer. For a conventional computer difficulty of breaking 256-bit key equals 256/2=128 bits. For a quantum computer it's just sqrt(256)=16 bits.
Seems Bitcoin is NOT safe. Or am I wrong?
Neither is every public private keypair in the world, by your logic. So don't do online banking. Or shop online. Or do credit card transactions.
Bitcoin is not the only thing not safe from the concept.