Tags

A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.

Qiskit is an open source SDK for working with quantum computers at the level of pulses, circuits and application modules. If appropriate, also use the [programming] tag.
For any questions whose answer is expected to require code or programming notions. For questions about a specific framework (e.g. qiskit or cirq) please also include a more specific tag. If your quest…
For questions regarding usage, performance, implementation, application or theory related to quantum gates.
Questions about or related to quantum states. Consider using the density-matrix tag when relevant.
For questions about quantum algorithms, that is, sequences of quantum gates, operations, and measurements, whose purpose which achieve some goal. Standard examples are Shor's and Grover's algorithms.
For questions about the principle and application of quantum entanglement. It is a physical phenomenon which occurs when pairs or groups of particles are generated, interact, or share spatial proximit…
for questions about IBM's Quantum Service - Circuit Composer & Quantum Lab. DO NOT use this for questions about general Qiskit issues (use [qiskit] for that).
592 questions
For questions about the construction of complex circuits using elementary quantum gates.
Applies to questions of primarily educational value - styled in the format similar to that found in textbook exercises. This tag should be applied to questions that are (1) stated in the form of an ex…
For questions related to measurement and its effects as relevant to quantum computation and quantum information.
for questions about mathematics relevant to quantum computing and/or quantum information theory. DO NOT use this tag for general mathematics questions.
Quantum error correction (QEC) is a collection of techniques to protect quantum information from decoherence and other quantum noise, to realise fault-tolerant quantum computation. Quantum error corre…
For questions about completely positive (CP) linear maps between quantum states. Can also be used for trace-preserving CP maps (quantum channels). For questions about unitary operations, please use qu…
Grover's search algorithm is an algorithm that can perform a search in the order of square root of the input size. This is a provable speed up over the best classical algorithm, which requires a time …
289 questions
a model in which a computation is a sequence of quantum gates, which are reversible transformations on an n-qubit register (the quantum-mechanical analog of an n-bit register)
For questions about simulating either quantum computers or simulating things on quantum computers.
For questions about density matrices and related concepts and ideas, e.g. procedures for computing properties of quantum states from their density matrices.
For questions about exercises or passages from the popular quantum computing textbook *Quantum Computation and Quantum Information* by Michael Nielsen and Isaac Chuang.
For questions that involve a request for resources to learn anything related to quantum computing or quantum information.
245 questions
For questions regarding complexity analysis of quantum algorithms and comparisons with complexities of classical algorithms.
223 questions
Hamiltonian simulation is a class of algorithms that, given a Hermitian matrix A, output a quantum circuit implementing an approximation to the unitary exp[iAt].
For questions about physical implementations of a quantum algorithm or other quantum information protocol. DO NOT use for questions about simulation or emulation of quantum computers, or cloud-based q…
194 questions
For questions about the Variational Quantum Eigensolver, a quantum/classical hybrid algorithm that can be used to find eigenvalues of a (often large) matrix H. When this algorithm is used in quantum s…
186 questions
used for questions connected with information theory in classical and/or quantum sense.
185 questions
For questions about finding (short) gate sequences to implement a specific unitary operation, for example decomposing a complicated multi-qubit gate into a sequence of basic gates. It might apply to o…
167 questions
For questions about Pauli matrices in general or Pauli gates in particular, as relevant to quantum computing and/or quantum information theory. The Pauli matrices are a set of three 2 × 2 complex matr…
For questions related to the Bloch sphere. In quantum mechanics, the Bloch sphere is a geometrical representation of the pure state space of a two-level quantum mechanical system (qubit), named after …
153 questions
For questions related to the unitarity (unitary evolution) of quantum systems, as applicable to quantum computing or quantum information.
153 questions
Q# is a domain-specific programming language used to express quantum algorithms. This tag should be used for questions related to creating/programming quantum algorithms using the 'Q#' language. If th…
144 questions
For questions about matrix representations of quantum gates.
144 questions
A python framework for creating, editing, and invoking Noisy Intermediate Scale Quantum (NISQ) circuits. It is a Python library for writing, manipulating, and optimizing quantum circuits and running t…
143 questions
For questions about different types of noise a quantum computer (or qubits) may experience; how this affects the outcome of the computation; how to reduce a specific type of noise on a specific implem…
140 questions
Shor's algorithm, named after American mathematician Peter Shor, is a quantum algorithm for integer factorization, formulated in 1994. Informally, it solves the following problem: given an integer N, …
138 questions
For questions related to physical realizations of quantum bits i.e. quantum systems living in a 2-dimensional Hilbert space.
137 questions
For questions concerning how to improve quantum computers on different aspects like performance, efficiency or fault-tolerance.
Quantum Fourier Transform (QFT) is a linear transformation on quantum bits and is the quantum analogue of the discrete Fourier transform. The quantum Fourier transform is a part of many quantum algori…
133 questions
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