GLOSSAIRE

Boson Sampling is a specialized model of quantum computation that involves sampling from the probability distribution of identical bosons (typically photons) scattered through a linear optical network. This quantum approach […]

What is Single-Photon Source Brightness? Single-photon source brightness refers to the efficiency with which a device emits usable single photons. It is typically defined as the probability that a single […]

Computational complexity studies the resources (mostly, time and space) required to solve a problem on a computer. It classifies problems based on how difficult they are to solve for different […]

What are the DiVicenzo criteria?  The DiVincenzo Criteria (find the paper here) are a set of fundamental requirements formulated by physicist David DiVincenzo in 2000 that define the necessary conditions […]

General ideas  Data can be affected by “noise”, that is, any unwanted interactions with the rest of the environment which result in a modification of the data. This leads to […]

An error-corrected qubit is a logical qubit that is protected from errors using quantum error correction (QEC) techniques. More precisely, error-corrected qubits are highly-entangled quantum states where one or several […]

FTQC, which stands for Fault-Tolerant Quantum Computing, refers to the ability of a quantum computer to continue operating correctly in the presence of errors and faults. It involves sophisticated techniques […]

Definition A hybrid quantum–classical algorithm is a computational scheme in which a quantum computer and a classical computer collaborate to solve a problem. The quantum circuit handles subroutines that can […]

What is Linear Optical Quantum Computing?  Linear Optical Quantum Computing (LOQC) is a paradigm of quantum computing that uses photons as qubits and manipulates them using only linear optical elements […]

The term “logical qubit” can be used in two contexts, with slightly different meanings. It can be meant as a mathematical concept that represents a perfect quantum bit, i.e. the […]

What is a Measurement A measurement is an operation which happens during or in the final step of a quantum computation. Usually, measurements are used in the end to average […]

NISQ, which stands for Noisy Intermediate-Scale Quantum, refers to the current generation of quantum computers. These devices have several tens to a few hundred qubits and are characterized by their […]

Noise is a broad concept that includes all imperfections and unwanted processes that may occur during a computation, degrading its output.   Ideally, the quantum system that hosts the computation should […]

A photonic gate is a fundamental building block in optical quantum computing and quantum information processing. Photonic gates are used to manipulate a quantum state encoded in photons and perform […]

Early electronic computers, such as ENIAC in the 1950s, were built using bulky components that required a significant amount of space. Over time, advancements in semiconductor technology led to compact, […]

What is a Photonic Qubit? A Photonic Qubit is a quantum bit encoded in the quantum states of light. At the quantum level light is made up of individual particles […]

A physical qubit can be any physical system able to encode a qubit degree of freedom, i.e. well defined and manipulable |0> and |1> states. Two-level physical systems are ideal […]

Quantum as a Service (QaaS) refers to cloud-based platforms that provide access to quantum computing resources over the internet. This model allows users to run quantum algorithms and experiments on […]

When people first hear about quantum computing, a frequent question is “what is the point in trying to build such a quantum computer?”. The answer to this very important question […]

What is AI: Artificial intelligence (AI) is a field of research in computer science that refers to the capability of computers to perform tasks typically associated with human intelligence, such […]

A quantum algorithm is a sequence of operations that can be performed only on a quantum computer. Such algorithms exploit properties inherent to quantum systems, such as entanglement, superposition and […]

Quantum annealing is a quantum computing paradigm particularly suited to solving optimization problems, including some NP-complete problems, such as the traveling salesman problem. Contrary to gate-based approaches, quantum annealing will […]

A benchmark is a condition against which we can judge that a quantum device is “good enough” in some sense – usually many different benchmarking metrics are required. Benchmarking is […]

They are analogous to classical logic circuits but operate on qubits according to the principles of quantum mechanics.  A quantum circuit consists of a series of initializations , quantum gates […]

Classical computers (laptops, mobiles phones, gaming consoles…) are built around the concept of “bits”. Bits are binary units of information, meaning that a bit can take the values \(0\) or […]

Quantum Computing is a revolutionary approach to computation that harnesses the principles of quantum mechanics to process information. Unlike classical computers that use bits (0s and 1s), quantum computers use […]

Decoherence is a phenomenon where a quantum system loses its coherence, or quantum behavior, due to interactions with its environment. It’s the process by which the quantum nature of a […]

A quantum dot (QD) is a nanoscale semiconductor structure that exhibits unique optical and electronic properties due to quantum mechanical effects. These structures are typically a few nanometers in size […]

What is a quantum energetic advantage?  The development of quantum computers was primarily motivated by their computational advantage, that is, the fact that quantum computers can solve tasks which are […]

Quantum entanglement is a fundamental quantum phenomenon where two or more particles become correlated in such a way that the quantum state of each particle cannot be described independently, even […]

Definition A quantum feature map is a method for encoding classical data into quantum states, allowing machine learning algorithms to operate in high-dimensional Hilbert spaces. By mapping data into this […]

Quantum information is fragile and needs to be protected from various sources of errors. This is usually done by spreading the quantum information into a bigger system, called a quantum […]

Machine learning (ML) is a subfield of artificial intelligence where algorithms are not explicitly programmed, but rather learn directly from the data, or from experience, i.e. interacting with an environment.  […]

Quantum Mechanics is a fundamental theory in physics that describes the behavior of light and matter at the molecular, atomic, nuclear, and even smaller microscopic levels. It provides a mathematical […]

The idea of a quantum simulator was proposed by Yuri Manin in 1980 and Richard Feynman in 1982 who famously wrote: “Nature isn’t classical, dammit, and if you want to […]

What is quantum software?  Quantum software is a form of specialized software with the aim to make the implementation of quantum algorithms possible. It contains several different tools that are […]

Superposition is a phenomenon where a quantum system can exist in multiple states simultaneously. Unlike classical systems that must be in one definite state at any given time, a quantum […]

What is Quantum Volume? Quantum volume is a benchmark used for assessing generic quantum circuit performance. The benchmark consists of applying sequences of random gates and checking whether, at a […]

Definition Quantum-inspired algorithms are classical algorithms that leverage mathematical techniques and concepts originally developed for quantum computing. They run entirely on conventional hardware (CPUs, GPUs, TPUs) but mimic certain aspects […]

A qubit is the fundamental unit of quantum information, existing in a superposition of two basis states simultaneously. Unlike classical bits, qubits can represent a continuum of states between 0 and 1, enabling the unique computational capabilities of quantum systems.

Shor’s algorithm, introduced by Peter Shor in 1994, is a foundational quantum algorithm designed to factor large integers efficiently. This problem—factoring composite numbers into their prime components—is widely regarded as […]

A Single Photon Source (SPS) is a specialized device or system that can emit exactly one photon at a time, either on demand or with high probability. These sources are […]

A quantum gate is a single operation performed in a Quantum circuit, which modifies the logical state of the qubits involved in the computation according to some predetermined rules.  How […]

How does SPAM error work? It is convenient to label different sources of noise in a quantum device (as there are usually many) and we categorize them to better understand […]

A superconducting qubit is a type of physical qubit, which is implemented using superconducting circuits (see below). The first experimental demonstration of such qubits was achieved in 1999, shortly after […]

A trapped ion qubit is a type of physical qubit, which consists of an atomic ion suspended, or trapped, in an electromagnetic field — an ion being an electrically charged […]

A two-qubit gate is an operation that acts on two qubits throughout a quantum computation. Depending on the operation, the qubits, after the application of the two-qubit gate, can be […]

Variational quantum algorithms (VQAs) are a type of hybrid classical-quantum algorithms consisting of a parametrized quantum circuit and a classical optimization loop to update the parameters of the quantum circuit.   […]