Quantum Information Science The New Frontier in Quantum Computation, Secure Communication, and Sensing

The prospect to perform certain computational tasks, such as search, optimization, and simulations much faster than what conventional computers can ever achieve, has fueled the development of Quantum Information Science and related fields for about three decades. Quantum entanglement, which makes it possible that more than one particle can be described by the same wavefunction, as well as the superposition of states are unique phenomena in quantum mechanics. They enable exciting new ways to process, transmit, and obtain information. See the chart below for the main branches that make up the exciting new field of Quantum Information Science, which - while still in its infancy - has the potential to change the world as we know it in the next decades. Due to rapid progress during the past years, the book includes selected research published mostly between 2016 and 2018. It starts with an introduction chapter that includes a short update of this new bur rapidly evolving field and two related unique phenomena like the observation of nonlocal position-changes of a photon and the concept of spatio-temporal steering. The latter is a new way to assess nonclassical correlations in an open quantum-network. This is followed by a large section on quantum computing, which begins with reviews of the progress of trapped-ion processors focusing on laser-based quantum gates and twisted photons that enable more than two states - so called qudits. Silicon-based architectures, components and semiconductor-inspired design principles for quantum computers are described in the following papers before several types of quantum algorithms are reviewed, including quantum genetic algorithms and a complete 3-qubit Grover search-algorithm. The end of the computing chapter is marked by a series of papers on quantum machine-learning - a field with the potential to accelerate the development of artificial intelligence considerably. Machine-learning-related themes here-include the dramatically improved performance through reinforcement learning, and quantum entanglement in neuronal network states that focuses on the restricted Boltzmann-machine architecture. The section on quantum cryptography and sensing starts with an investigation of the fundamental limits for repeaterless quantum communication which provides precise and general benchmarks for quantum repeaters. The ability to quantum-process already encrypted data is then investigated, which opens new avenues for secure cloud-computing. A secure communication alternative to quantum key distribution, quantum secure direct communication, was experimentally realized in the next paper. The book finishes with three papers on quantum sensing i.e. quantum metrology. These studies show how rendering the dynamics of quantum sensors chaotic can enhance the sensitivity without relying on the preparation or stabilization of highly-entangled states. Furthermore, it is found that the Heisenberg limit can be approached by using quantum error-correction and that the synchronization of distant optical docks at the femtosecond level is possible. Book jacket.