The computations used to do symmetric and asymmetric encryptions are completely different. Asymmetric encryption is just about factoring out big numbers into primes, if we simplify things a bit. And modern computers aren't very good at it, but Quantum Computer happens to be, and can break it. Read a bit about Shor's Algorithm[0].
On the other hand, symmetric encryption can be seen as a super convoluted and costly shift cipher. And it seems that Quantum Computing does not help much with dumb and costly mathematics like this.
On the other hand, symmetric encryption can be seen as a super convoluted and costly shift cipher. And it seems that Quantum Computing does not help much with dumb and costly mathematics like this.
[0]: https://en.wikipedia.org/wiki/Shor%27s_algorithm