When I say that quantum computing is not possible, I mean in general. It's a dead end. Note that this belief is subject to being falsified by progress in the field or a demonstration of error correction at scale.
There are companies selling and companies using "Quantum Computers". For example, D-Wave systems sells a computer that uses quantum annealing so solve a class of minimization problems.
To date, there is no quantum computer, in a commercial or a research setting, that has demonstrated it can compute anything faster than a classical computer (this includes the D-Wave systems).
The current trend is to try to establish quantum supremacy (and thus falsify the error correction is impossible thesis) through building extremely simple (non-general purpose) quantum systems. Most recently Google announced a successful attempt that has since been invalidated.
There are companies selling and companies using "Quantum Computers". For example, D-Wave systems sells a computer that uses quantum annealing so solve a class of minimization problems.
To date, there is no quantum computer, in a commercial or a research setting, that has demonstrated it can compute anything faster than a classical computer (this includes the D-Wave systems).
The current trend is to try to establish quantum supremacy (and thus falsify the error correction is impossible thesis) through building extremely simple (non-general purpose) quantum systems. Most recently Google announced a successful attempt that has since been invalidated.