Principles of Quantum Mechanics

Chapter 20

Introduction to Quantum Computing

If you do not expect the unexpected, you will not find it.

—Heraclitus

20.1  INTRODUCTION

All modern day computers use two-state binary logic in data processing (or information processing). The size of the modern day computers (we shall call these as classical computers, as their size is macroscopic) is decreasing day-by-day at the rate predicted by Moore. Moore’s law may be stated in various forms:

1. The computing power will double for constant cost roughly every two years.
2. The number of components (transistors) in silicon ICs will roughly double every two years.
3. Minimum feature size of an IC chip halves roughly every two years.
4. The computer size halves roughly every two years.

So at this exponential ...