Quantum Computing. Hafiz Md. Hasan Babu

       22.2.2 The RC encoder with single-feedback

       22.2.3 The RC encoder with multi-feedback

       22.3 Summary

       Further reading

       23 The QCA multiplexer and demultiplexer

       23.1 The QCA 2-to-1 multiplexer

       23.2 The QCA 4-to-1 multiplexer

       23.3 The QCA 1-to-2 demultiplexer

       23.4 The QCA 1-to-4 demultiplexer

       23.5 Multiplexing/demultiplexing using QCA

       23.5.1 The effect of the selector line (S0,S1) on the 2-to-1 MUX/1-to-2 DEMUX

       23.6 Summary

       Further reading

       24 The QCA RAM, ROM, and processor

       24.1 The RAM cell

       24.2 The QCA ROM

       24.3 The QCA processor

       24.3.1 Instruction memory

       24.3.2 Data memory

       24.3.3 The arithmetic logic unit

       24.3.4 The integrated processor

       24.4 Summary

       Further reading

      To my beloved parents and also to my beloved wife, daughter, and son, who made it possible for me to write this book.

Preface

      With the advent of nanotechnology, quantum computing is increasingly playing a large role in developing more compact and lower power consumption computers. The use of the properties of quantum mechanics has increased the speed certain computations dramatically. Quantum computing is one of the most promising nanotechnologies for designing modern compact computers. The quantum computer is an entirely different concept than the traditional computer and it does not use binary logic. Quantum computers can assess more than one probability at a time through something called quantum entanglement.

      The switching and memory units of a computing system are becoming as small as an atom, and switching techniques have reached their peak of development. Therefore, it is necessary to discover an entirely new way of thinking to build computing machines. Recently, advances in mathematics, materials science, and computer engineering have transformed quantum computing machines from theory to practice.

      This quantum computing book covers basic quantum computing, fault-tolerant quantum computing, and quantum dot cellular automata (QCA). The basic quantum computing part of this book comprises designs for different quantum circuits, including the adder, multiplier, divider, encoder, decoder, barrel shifter, comparator, and arithmetic logic unit. These quantum circuits are the building blocks of a quantum computer. Readers will obtain an understanding of quantum computing from the basic to the advanced level, which will help them to design new quantum circuits.

      The discovery of quantum error correction has greatly improved the long-term prospects for quantum computing technology. Encoded quantum information can thus be protected from the errors that arise due to uncontrolled interactions with the environment, or due to imperfect implementations of quantum logical operations. The fault-tolerant quantum computing part of this book consists of the designs for different fault-tolerant quantum circuits, such as the adder, multiplier, and divider. Fault tolerance is a very complex part of making a quantum circuit. It is necessary to develop fault-tolerant circuits which allow the qubits to be protected from quantum errors produced by inadequate control of environmental interactions. Readers will obtain a clear understanding of fault-tolerant quantum circuits and will be able to design their own fault-tolerant circuits.

      QCA are a new computational paradigm which encode binary information by charge configuration within a cell instead of the conventional current switches. As there is no current flow, the Coulombic interaction is sufficient for computation. This revolutionary paradigm provides a possible solution for transistorless computation at the nanoscale. Readers will obtain knowledge on QCA and the design processes of different quantum circuits using QCA design software. They will be acquainted with the costs of QCA circuits, which include cell area, delay, kink energy, and power.

      As a whole, this book is a great resource for quantum computing researchers and students alike. There are very few books written in this field. This book will satisfy the interest of beginner to advanced level readers.

Acknowledgments

      I would like to express my sincerest gratitude and particular appreciation to the various researchers in the field of quantum computing. The contents in this quantum computing book have been compiled from a wide variety of research works, where the researchers are pioneers in their respective fields. All the research articles related to the contents are listed at the end of each chapter.

      I am grateful to my parents and family members for their endless support. Most of all, I want to thank my wife Mrs Sitara Roshan, my daughter Ms Fariha Tasnim, and my son Md Tahsin Hasan for their invaluable cooperation in completing this book.

      Finally, I am also grateful to all of those who have provided their support and valuable time to finish this book.

Author biography

      Hafiz Md Hasan Babu

      Dr Hafiz Md Hasan Babu is currently working as the Pro-Vice-Chancellor of the National University, Bangladesh. He is on deputation from the Department of Computer Science and Engineering, University of Dhaka, Bangladesh. He is also a Professor and the former Chairman of the same department. Due to his excellent academic and administrative capabilities, he also served as the Professor and founder Chairman of the Department of Robotics and Mechatronics Engineering, University of Dhaka, Bangladesh. He served as a World Bank Senior Consultant and General Manager of the Information Technology & Management Information System Departments of Janata Bank Limited, Bangladesh. Dr Hasan Babu was the World Bank Resident Information Technology Expert of the Supreme Court Project Implementation Committee, Supreme Court of Bangladesh. He was also the Information Technology Consultant of the Health Economics Unit and Ministry of Health and Family Welfare in the project ‘SSK (Shasthyo Shurokhsha Karmasuchi) and Social Health Protection Scheme’ under the direct supervision and funding of the German Financial Cooperation through KfW.

      Professor Dr Hafiz Md Hasan Babu received his MSc degree in Computer Science and Engineering from the Brno University of Technology, Czech Republic, in 1992 under a Czech Government Scholarship. He also obtained a Japanese Government Scholarship