Chapter 16 - The quantum internet and hybrid quantum technology

Abstract

The quantum internet is a proposed network of interconnected quantum computers. It is hoped that it will someday send, compute, and receive information encoded in quantum states. But it is not intended to replace the modern or “classical” internet. Instead, the quantum computer will provide new functionalities such as quantum cryptography and quantum cloud computing. However, unlike conventional computer bits—which convey information as a 0 or 1—qubits or quantum bits convey information through a combination of quantum states, which are unique conditions found only on the subatomic scale. Qubits are not either 0 or 1, but rather both and neither, in a quantum phenomenon called superposition, which allows them to be faster and can handle problems that would take extremely prohibitive long times on existing supercomputers. There are several different types of qubits in development, and each comes with distinct advantages and disadvantages. The most common qubits being studied today are quantum dots, ion traps, superconducting circuits, and defect spin qubits. But to harvest/unlock the potential, a quantum computer must be able to process many qubits—more than any single machine can manage now, motivating us to join several quantum computers through the quantum internet and their computational power pooled, creating a far more capable system. In this chapter we discuss the fundamentals and various elements of prospective quantum internets and networks. We cover the basic principle of quantum entanglement. Single atom entangles photons single and double photons-quantum repeater, entanglement of matter-matter (atom-atom) by radiative processes, swapping of entanglement, Bell and EPR pairs (measurement of entanglement of two qubits) and quantum teleportation, hidden variables in quantum mechanics, testing hidden variables, experiments on hidden variable theory, and status of entanglement and hidden variables. The chapter also introduces different types of qubits in development, presenting the distinct advantages and disadvantages of each type. The most common qubits being studied today are superconducting circuits, quantum dots, ion traps, and defect spin qubits. In addition to those we present the topics of hybrid superconductor-quantum dot configurations, qubits under strong fields, sudden death of entanglement, Stark induced nonlinearity, and strong coupling (Rydberg atom hybrid systems), strong field dressing (nonlinear interaction), cubic superconducting metal on silicon transmon qubit, acoustic waves and superconducting quantum qubits, and integration of Coulomb ion field and superconducting circuits. Moreover, the chapter covers hybrid quantum networking, gas-solid nodes, real-artificial atom (superconducting) nodes, integration of networking with supercomputing, quantum digital and analog (photons and waves) entangled photon pairs by nonlinear crystals, integrating superconducting circuits/cavities and semiconducting (super-semi) devices. Finally, we discuss the stability of hybridization of quantum technologies, security issue in quantum networks and impact of quantum internet on science and technology.