quantumcomputing is a software thing. Improving the hardware is a totally different thing.
I think this is mistaken. Quantum computing is both a hardware and a software thing. In fact, it is a completely new way of thinking about information processing.
Although you are right to say that quantum computations can be simulated on a regular PC by doing lots of matrix multiplications, the size of those matrices grows exponentially with the number of qubits. Therefore, simulating quantum computations seems to be intractible (in the complexity sense) for a regular computer.
Although current technology makes heavy use of quantum mechanical effects (tunneling in transistors for example) it is not appropriate for quantum computing. For that we need systems that retain their coherence, i.e. a large number of systems can be kept in a superposition for a long time, and we need to be able to perform coherent operations on those systems.
A large number of systems have been proposed for implementing quantum computers, including Nuclear Magnetic Resonance, ion traps, quantum optics, semiconductors and quantum dots. It is fair to say that all of these are at a proof of principle stage and a genuinely scalable architechture for quantum computing is still some years down the line.
By the way, a lot of new ideas in theoretical physics are being developed in trying to build and understand these machines, so it is a little inaccurate to say that this is `just technology' (although I do not think it is wise to try and draw an exact line between physics and technology). These ideas are also used in testing quantum theory itself, and have recently had some impact on our understanding of many-body quantum systems.
Of course, we also need developments in quantum algorithms and complexity (the software side if you like) in order to make this whole enterprise worthwhile, so that is currently also a very active area of research.