Quantum Information Processing: An Essential Primer (original) (raw)

2020, IEEE Journal on Selected Areas in Information Theory

Quantum information science is an exciting, wide, rapidly progressing, cross-disciplinary field, and that very nature makes it both attractive and hard to enter. In this primer, we first provide answers to the three essential questions that any newcomer needs to know: How is quantum information represented? How is quantum information processed? How is classical information extracted from quantum states? We then introduce the most basic quantum information theoretic notions concerning entropy, sources, and channels, as well as secure communications and error correction. We conclude with examples that illustrate the power of quantum correlations. No prior knowledge of quantum mechanics is assumed. I. INTRODUCTION Quantum phenomena provide computing and information handling paradigms that are distinctly different and arguably much more powerful than their classical counterparts. In the past quarter of the century, much progress has been made on the theoretical side, and experiments have been carried out in which quantum computational operations were executed on a small number of quantum bits (qubits). The US National Science Foundation has declared this general area to be one of the 10 big ideas for future investments. In June 2018, the science committee of the US House of Representatives unanimously approved the National Quantum Initiative Act (H.R. 6227, Public Law No: 115-368) [1] to create a 10-year federal effort aimed at boosting quantum science. Similar funding commitments have been made throughout the world. We have entered what is known as the Noisy Intermediate-Scale Quantum (NISQ) technology era [2]. This term refers to devices with 50-100 qubits (intermediate-scale), which is too few to have have full errorcorrection (noisy). Nevertheless, NISQ systems may be able to perform tasks that exceed the capabilities of today's classical digital computers, and may be useful tools for exploring many-body quantum physics. On the theoretical side, significant progress has been made in understanding the fundamental limits of