14 Jul 2022 5 min read

Glossary of Quantum Terms


The Advanced Encryption Standard (AES) has a key length of 256 bits, is practically unbreakable, and is used to protect data.


This is the Agency of National Security Systems Information, based out of France to ensure national security.

Asymmetric cryptography

This is known as secret-key cryptography which uses two sides of different keys (one public and one private) to encapsulate and decapsulate (Key Encapsulation Mechanism) or verify and sign (Digital Signatures)


In computing, bits are the size of any character or information in the computing environment, and in quantum computing, they represent the size of the information


The coherence of a qubit, roughly speaking, is its ability to maintain superposition over time. It is therefore the absence of “decoherence”, which is any process that collapses the quantum state into a classical state, for instance by interaction with an environment.


This refers to the ability of security hardware to swap algorithms, as per industry standards, without the need to rewrite applications.

A cryptographically relevant quantum computer

This enables a quantum computer to attack cryptographic systems that classical computers can’t.


This is Canada’s national cryptologic agency, providing the Government of Canada with information technology security and foreign signals intelligence.

Dark fibers

This refers to an optical fiber that is not yet lit, or put into use by a service provider.

Digital signatures

This s a mathematical scheme for verifying the authenticity of digital messages or documents.


This is an acronym for Elliptic Curve Cryptography, the key-based technique for encrypting data.


This is the European Union Agency for Cybersecurity (ENISA) which contributes to European cyber policy, enhances the trustworthiness of ICT products and services, and helps Europe prepare for cybersecurity problems.


Quantum entanglement is the physical phenomenon that occurs when a group of particles are generated, interact, or share spatial proximity.


Developed by the National Institute of Standards and Technology (NIST), the “Federal Information Processing Standard” (FIPS) are standards and guidelines for federal computer systems.

Harvest-now, decrypt-later

This has been defined in many ways, but ultimately it means taking someone’s data to store until it can be decrypted.

Information-theoretic security

Provides the tools that define the notion of security.


This is a key encapsulation method (KEM) designed to be resistant to cryptanalytic attacks with future powerful quantum computers. It is used to establish a shared secret between two communicating parties without an (IND-CCA2) attacker in the transmission system being able to decrypt it.


This stands for the National Cyber Security Center UK, which provides cybersecurity to make the UK the safest place to work online.


This is an acronym for Noisy intermediate-scale quantum which refers to the leading quantum processors which contain about 50 to a few hundred qubits. These are not advanced enough to reach fault-tolerance nor large enough to profit sustainably from quantum supremacy. The term was coined by John Preskill in 2018..


This is the National Security Agency, a federal government intelligence agency that is part of the United States Department of Defense.

PQC (post-quantum cryptography)

This refers to cryptography that is resilient against quantum computers, hence ‘post-quantum’.

Physical qubit

Physical qubits are physically realized qubits. They can be in superposition.

Quantum algorithm

This is an algorithm that runs on a realistic model of quantum computation, the most commonly used model being the quantum circuit model of computation. A classical (or non-quantum) algorithm is a finite sequence of instructions, or a step-by-step procedure for solving a problem, where each step or instruction can be performed on a classical computer.

Quantum key distribution (QKD)

This is a method that leverages the properties of quantum mechanics, such as the ‘no-cloning theorem,” to allow two people to securely agree on a key, a secret code word that is shared only between you and the person you are trying to communicate with. This secret code word can then be used to encrypt messages such that they can be transmitted without being read by a malicious third party.

Quantum Readiness Index (QRI)

This is a tool that is used to determine if an organization is quantum-safe. It measures the company’s readiness for quantum technology.

Quantum supremacy

Proof that the quantum computer is superior to the classical computer, based on tasks and outcomes.


A classical bit can be in two states, it can be either zero or it can be one. A quantum bit or qubit, however, can be in a sort of zero state and in a one-state at the same time. This situation is called a superposition of (quantum) states. Qubits have some very particular properties: for instance, it is not possible to make copies of qubits. This is sometimes very useful, such as when you want to keep information private, and in fact this property is used in quantum cryptography.


From QuSecure, this is the industry’s first end-to-end PQC software-based solution uniquely designed to protect encrypted communications and data with quantum-resilience using quantum secure channels. With QuProtect, for the first time organizations can leverage quantum resilient technology to help prevent today’s cyberattacks, while future-proofing networks and preparing for post-quantum cyberthreats.


This is one of the oldest public-key encryption systems used for data protection.

Stream Cipher

A stream cipher is a symmetric key cipher where plaintext digits are combined with a keystream. In a stream cipher, each plaintext digit is encrypted one at a time with the corresponding digit of the keystream, to give a digit of the ciphertext stream. Since encryption of each digit is dependent on the current state of the cipher, it is also known as a state cipher.


This is when, in classical physics, any two (or more) quantum states can be added together.


“Years to Quantum”, is the moment of uncertainty when we could lose digital security.

Sources include wikipedia.com, dictionary.com, and vocabulary.com.


Other news

Sorry, no posts matched your criteria.

Are you ready? Contact us today.

Find out more