This chapter discusses key questions to provide a foundation for understanding why quantum computers are different from classical computation: What is computation? How is computation different from calculation? What kinds of tasks can computers perform? What is complexity theory? This chapter discusses the early design and government patronage of computing. Critically, this chapter dispels the commonly-held belief that quantum computers have magical, universal powers to solve problems.

In this chapter we present our recommendations for how the policy landscape in the U.S. and other liberal democracies should respond to the opportunities and challenges brought on by quantum information science. These recommendations are informed by the four scenarios of quantum futures combined with the understanding of technology capabilities we discussed in Part I. We begin this chapter by putting our cards on the table and presenting our policy goals. We then explore how to achieve these goals using traditional policy levers: direct investments, education, and law. We conclude with a discussion of national security issues.

Introduces and outlines The Quantum Age: what are quantum technologies and what are the reasons why different institutions are interested in them now. The introduction discusses scenario analysis, likely scenarios for quantum technology deployment, and the high-level policy implications raised by them.

Presents the approaches to building a quantum computer, the different substrates being used to build a scalable quantum computer, the profound challenges in doing so, and finally, an outlook on how the scientific challenges and economic incentives will shape quantum computing projects.

The history of Quantum Computing and Quantum Cryptography starts with a friendship between Charles Bennett and Stephen Wiesner, two undergraduates at Brandeis University who toyed with ideas for sending information using quantum entanglement, and John Conway's Game of Life, which stimulated interest in cellular automata at MIT in the 1970s and started a generation of computer scientists wondering if the universe might be some massive computer running a simulation of reality. In 1974 MIT professor Ed Fredkin spent his yearlong sabbatical at Caltech, where he learned quantum physics from Richard Feynman while he taught Feynman about computer science. Returning to MIT, Fredkin's ideas developed into the philosophy of digital physics, which blossomed into the 1981 Conference on Physics and Computation at MIT. Feynman's keynote at the conference described how a computer based on quantum mechanics principles could compute physics simulations much faster than today's classical compu

This appendix explains quantum effects: uncertainty, entanglement, and superposition; and explains how these effects form the basis of quantum sensing, computing and communication. This appendix summarizes the history and debates of wave mechanics, which was developed at the start of the Twentieth Century. Examples are given of macro-level quantum effects that the reader can observe in an attempt to start building an intuitive sense of quantum effects. These macro-level quantum phenomena are the dual-slit experiment, black-body radiation, and the characteristics of polarized light. Much attention is given to the characteristics of light, both because light provides examples of quantum effects but also because photonic emitters and sensors play a key role in quantum sensing, computing, and communication.

Quantum sensing, computing, and communication offer some significant improvements on classical technologies, in some cases create fundamentally new capabilities. Quantum technologies are quickly arriving. Even if the most hyped promises in quantum computing are not realized in the next decade, in the near term quantum sensing could shift relationships irrevocably. This book has painted the landscape of quantum's implications---from nation-state concerns of strategic conflict, intelligence gathering, and law enforcement activities; to the concerns of companies that may be subject to industrial policy priorities and restrictions; to the level of the individual who may face institutions with great asymmetries in sensing and sense-making power. This chapter concludes with a forecast of quantum technology scenarios, with forecasts for each quantum technology analyzed in this book, and with a summary of the most important policy issues to pursue.