How to Build a Quantum Computer

The challenge of building a quantum computer is that the states of the machine cannot be measured before the computation has run its course. Any such measurement destroys the fragile superposition of states that characterize the quantum world (but not the classical world). At the same time, these quantum states have to be controlled so that initialization, computation, and, eventually, readout, can be performed. This talk will consider a few candidate systems and report on progress in the lab (including the speaker’s). The quantum bits operate near absolute zero and self destruct in less than a millisecond. When will this be a technology? Is a quantum computer around the corner, already here, or 50 years away (and always will be)? And, once here, what’s it good for?