Pretty much: Quantum Computers (QCs) can factor numbers (Shor's algorithm) and calculate discrete logarithms in polynomial time. I don't know whether there's an algorithm for hash-calculation that will let someone dominate the BitCoin hashing chain with a QC though.
On the other hand, no one actually knows whether it's possible to build a quantum computer with enough q-bits that will stay coherent for long enough to carry out the calculation: as you add q-bits, noise becomes more and more of a problem. You can add error correction, but that makes keeping all the q-bits coherent harder because now you've got even more of them! At the moment, no-one knows (unless the NSA has built one and isn't telling!) which effect is going to win out as the number of q-bits increases.
(You can't use a smaller QC to simulate a slower version of a larger one, unlike in the non-quantum computing world: if you need to factor a 1024 bit number and you only have a 1000 bit QC you can't do it, as I understand things.)
Note that Quantum Computers don't help as much with symmetric encryption, unless someone comes up with a much better algorithm. They let you effectively halve the key-space, which is a fairly big deal, but you can get back to the same level of difficulty by doubling up the size of your keyspace: a 256-bit AES key provides roughly the protection of a 128-bit key in a quantum computing world. This is different to public-key encryption, where you can double the key size, but if your opponent has a quantum computer with enough q-bits, they can still break your new key in reasonable time.