An Introduction to Quantum Computing

To begin with let us look at regular digital computers, or what physicists call a classical computer. This performs data processing tasks by manipulating bits; each bit can have a value of one or zero. A quantum implementation of a computer manipulates quantum bits (qubits). Qubits can have a value of one, zero or both simultaneously. When the bit is simultaneously a one and a zero, (yes one and zero at the same time, not oscillating quickly between two states) the bit is said to be in a state of superposition. Superposition is one of two key phenomena in quantum computing, the other being entanglement as they allow us to quickly crack encryption, make artificial intelligence (AI) faster, or do things like simultaneously build models for weather and the stock market.

In this article we will focus on superposition. To understand this, we need to examine the properties of an electron, especially how electrons behave in the presence of electromagnetic (EM) fields and how this is used within qubit. Consider figure 1. Each atomic orbital is represented by an energy level measured in electron volts (eV), with the lowest orbit called the ground state. As a particle can also be a wave (wave-particle duality), its energy level has a frequency equal to the energy level in eV divided by Planck's constant (the quantization constant). If we want the electron to move to a higher energy state, we apply EM energy at a frequency equal to the desired energy level minus the current energy level, divided by Planck's constant. The frequency and time the stimulus is applied is key, plus if we can constrain the energy levels to two, we have the fundamental building blocks for manipulating 1s and 0s with a single electron.