The ultimate parallel computer is a quantum computer. Quantum computing pioneer David Deutsch controversially argues that “quantum computers share information with huge numbers of versions of themselves throughout the multiverse,” and can get answers faster here in our Universe by in a sense getting help from these other versions.4 We don’t yet know whether a commercially competitive quantum computer can be built during the coming decades, because it depends both on whether quantum physics works as we think it does and on our ability to overcome daunting technical challenges, but companies and
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