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How is a quantum  computer operated?

I would like to know about quantum computing, how it is operated.

For digital computers (digits mostly as bits, but could be anyting able to hold a specific finite number of states) there is an input, as a series of digits, a program that consists of a sequence of instructions, and an output, again as a series of digits.

It wasn't always so, the sequence of instructions missing on electric analog computers and the input and output would be a time-dependent signal of varying voltage.

Even earlier, a watch is a cog wheel based computer where the input is the initial adjustment of the hands on the dial and the output is their subsequent positions changing with time.

What I like to know about quantum computers: what is the input, how is the output collected and is there some kind of "program", a series of instructions, or does it have to be redesigned for every new kind of task?