The Engineering Research Center (ERC) for Quantum Networks (CQN) will take on one of the great engineering challenges of the 21st century: to lay the technical and social foundations of the quantum internet. The quantum internet will surpass the capabilities of today's internet because of the unique advantages of entanglement, a coordination of the quantum states of particles serving as computational bits that is not present in the realms of classical physics. Quantum entanglement will improve the internet in at least two important ways. First, it will enable physics-based communication security that cannot be compromised by any amount of computational power. Second, the quantum internet will create a global network of quantum computers, processors, and sensors that are fundamentally more powerful than today's technology. This will bring unprecedented advances in distributed computing and enable secure access to quantum computers for the public. As the architects of the ARPANET could not fathom the full range of applications of the modern internet, the impact of the CQN ERC may be similarly profound and multifaceted. The quantum internet can help revolutionize national security, data privacy, drug discovery, novel material design, and push the frontiers of science with ultra-sensitive telescope conglomerates tied together with entanglement. In addition to the technical innovation, CQN will work to ensure that society is well prepared for broad, affordable, and equitable access to the quantum internet and its economy. CQN ERC will proactively study the social and policy implications of this budding technology and will bring a basic understanding of quantum technology to diverse communities. At the university level, CQN will contribute to development of a new discipline--Quantum Information Science and Engineering (QISE). CQN will also develop other curricular innovations that help train a diverse workforce of quantum engineers who can intuit radically new applications of quantum information science in socially responsible ways. Under the unique leadership of a quantum information scientist, a quantum engineer, and a technology policy expert, this highly interdisciplinary University of Arizona led ERC draws from core partner institutions Harvard, MIT, and Yale - along with member institutions UMass Amherst, University of Oregon, Northern Arizona University, Howard University, University of Chicago, and Brigham Young University. CQN also enjoys the support of a strong industry consortium and the leading international partners in advancing quantum internet technology. The CQN ERC will help to support the strategic vision that is laid out in a 2020 White House memorandum on America's Quantum Networks. The technical goal of CQN ERC is to develop one of the world's first long-distance quantum communications networks enabled by fault-tolerant quantum repeaters, supported on a network backbone of quantum repeaters and switches. These quantum repeaters are special-purpose quantum processors that will enable high-speed communication of qubits (quantum bits that live in a superposition of 0 and 1) over a long distance. Equipped with quantum memories built with vacancy defect centers in diamond, and spin-photon interfaces to connect them to the modern telecommunications infrastructure, the quantum repeater and its key subcomponents will be tested, validated and improved in two testbeds (in Tucson and Boston). A team of computer scientists and network engineers will work with physicists and material scientists to design architectures and protocols for a quantum internet that seamlessly interoperates with the classical internet. Engineering R&D will coordinate with social science research on security and privacy laws, unintended biases in quantum-network-driven applications, and implications of open-source quantum cloud access. As a public-private partnership of academia, the industrial base, leading international partners, national labs and equity partners, the CQN ERC will serve as a national hub for advancing the development of the quantum internet and road mapping its anticipated applications and societal impacts. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.