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.

This chapter uses scenario analysis to seed a policy discussion for quantum technologies. We envision four likely outcomes of the quantum technology race, and these different visions provide motivation for contemplating the strategic, political, and social dimensions of quantum technologies.

This chapter explains two categories of quantum communications technologies: quantum random number generation and quantum networking (or ``quantum internet''). If the quantum networking necessary to achieve the ideal of a quantum internet were achieved, one could likely use the technology to connect disparate, small quantum devices into a larger cluster computer, or connect multiple quantum computers together to create a larger quantum computer. The chapter sets the stage for interest in quantum communications by briefly explaining the rise of signals intelligence (SIGINT) capabilities of governments and the proliferation of these powers to non-governmental actors.

Quantum sensing is the most exciting quantum technology and it has the most potential to change our lives in the next decade and beyond. Quantum sensors will offer new capabilities with benefits for medicine, defense, intelligence, extractive industries and many others. Quantum sensing is a precursor technology to quantum computing and communications. Quantum sensors use quantum properties and effects to measure or sense physical things. This chapter explores quantum sensing as a topic in its own right, because the capabilities of quantum sensing are surprising and offer new forms of knowledge discovery and at new levels of analysis. Furthermore quantum sensors are here today---indeed, they have been in use for more than fifty years.

Introduces Law and Policy for the Quantum Age, with a discussion of the key phenomena needed to understand quantum mechanics: the uncertainty principle, entanglement, and superposition.

The risk of wide-scale cryptanalysis pervades narratives about quantum computing. We argue in this chapter that Feynman's vision for quantum computing will ultimately prevail, despite the discovery of Peter Shor's factoring algorithm that generated excitement about a use of quantum computers that people could understand---and dread. Feynman's vision of quantum devices that simulate complex quantum interactions is more exciting and strategically relevant, yet also more difficult to portray popular descriptions of technology. The Feynman vision for quantum computing will lead to applications that benefit humans in multifarious and unforeseen ways, just like the classical computing revolution improved our lives. Feynman's vision may also enable a ``winner-take-all'' outcome in building a large quantum computer. \par To explain this outcome, we canvass the three primary applications that have been developed for quantum computing: Feynman's vision of simulating quantum mechanical

This appendix situates quantum technologies as a product of the merger of quantum mechanics, the theory of the very small; and information theory, the theory of how information is communicated and quantified. These intersections of these fields create quantum information science (QIS), provide a basis for understanding quantum sensing, computing, and communication. This appendix explains quantum scale and starts an exploration as to why effects at the quantum scale are so radically different from humans' day-to-day experience.