# A Quantum Glossary

## Contents

**A Quantum Glossary**¶

Here are some of the terms that we’ve encountered.

## Diffraction¶

This is the *spreading out* of a wave as it encounters the edge of a barrier.

Think about how the light in a corridor spreads out into a dark room whose door is slightly ajar.

## Entanglement¶

A phenomenon whereby two or more quantum objects cannot be *mathematically described* separate from each other. It is associated with strange quantum correlations, irrespective of spatial distance separating the objects.

## Interference¶

This is when waves can add up and/or cancel each other out.

If waves are *in phase*, they add to each other. If they are *out of phase*, they cancel each other.

## Quantum algorithm¶

Definition: A sequence of computational steps for a quantum computer to follow.

## Quantum Mechanics¶

The *mathematical* and *physical* theory developed to describe the behaviours of quantum objects and systems.

## Qubit¶

A qubit is a *quantum bit*. A quantum bit is the basic unit of *quantum information* and essentially, the building blocks of quantum computers.

## State¶

The *state* of a *physical* object is simply its description in a particular context/setting.

## Superposition¶

The ability of *quantum objects* to be in two or more, measurably distinct states *at the same time*.

## Wave-function¶

The *mathematical function* that describes the *state* of a quantum object/system.

## Wave-function collapse¶

This refers to a phenomenon that occurs when quantum objects/systems are observed or measured. Wave-function collapse is the *reduction* of a superposed state to one of the measurable states.

## Wave-particle duality¶

The ability of tiny objects to display both *wave*-behaviour and *particulate* behaviour in different experimental settings. The idea of wave-particle duality revolutionized Physics.