11.10 Summary

In this chapter, we connected the “logical” idea of qubits and circuits with the “physical” reality of how you might build a quantum computer.

Physical qubits don’t survive forever, and decoherence explains the several ways in which quantum states wander over time. While we do not yet have large enough systems to implement fault tolerance, we examined what error correction might be able to do in the quantum realm.

We need to be able to measure the progress we are making and answer questions such as “How powerful is your quantum computer?”. Our discussion of benchmarks looked at many factors that can affect performance.

We mentioned several technologies that researchers are exploring to implement qubits. According to their proponent scientists and engineers, superconducting transmon qubits, cold atoms, ion traps, and photonic techniques all hold promise.

We looked at the polarization...