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.

For questions related to the quantum algorithm for inverting linear systems of equations, developed by Harrow, Hassidim and Lloyd in 2009.
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…
99 questions
For questions concerning how to improve quantum computers on different aspects like performance, efficiency or fault-tolerance.
98 questions
For questions about the Quantum Approximate Optimization Algorithm (QAOA), first introduced in Farhi, Goldstone, Gutmann 2014 (https://arxiv.org/abs/1411.4028).
For questions about cryptography as it relates directly to quantum computing. Not for general cryptographic methods.
97 questions
For questions about the various kinds of entropies --- as defined in the context of quantum information theory and quantum statistical mechanics.
96 questions
Quantum teleportation is a process by which quantum information (e.g. the exact state of an atom or photon) can be transmitted (exactly, in principle) from one location to another, with the help of cl…
91 questions
Single qubit Hadamard gate transforms standard basis states (zero and one states) to their superpositions (plus and minus states)
90 questions
For questions about IBM's quantum computing processors and devices. For their cloud-computing service use the [ibm-q-experience] tag instead.
90 questions
For questions related to building of quantum computers and discussion of the hardware aspects.
89 questions
A tensor is an abstract object generalising a scalar or vector and can be represented by a number, a 1D array, 2D matrix or higher order generalisations thereof. A tensor product is a product defined …
87 questions
"Quantum advantage" or "quantum supremacy" is the potential ability of quantum computing devices to solve problems that classical computers practically cannot.
87 questions
For questions about the usage of, origin of or reasons for specific notation used in the context of quantum computing.
Refers to the quantum algorithm used to estimate the eigenvalue corresponding to an eigenvector of a unitary operator. (Wikipedia)
A stabilizer quantum error-correcting code appends ancilla qubits to qubits that we want to protect. A unitary encoding circuit rotates the global state into a subspace of a larger Hilbert space. This…
81 questions
Quantum superposition is a fundamental principle of quantum mechanics. It states that, much like waves in classical physics, any two (or more) quantum states can be added together ("superposed") and t…
79 questions
For questions about the set of quantum gates that form a set of gates from which another gate can be produced; this set is analogous the classical set of universal gates (either a NOR gate or a NAND g…
79 questions
In quantum information theory, fidelity is a measure of the "closeness" of two quantum states. It expresses the probability that one state will pass a test to identify as the other. The fidelity is no…
78 questions
For questions about vector spaces of all dimensions and linear transformations between them, including systems of linear equations, bases, dimensions, subspaces, matrices, determinants, traces, eigenv…
74 questions
For questions about either: comparing the performance of a quantum algorithm with a classical algorithm (or set of classical algorithms) independent of devices; or the ratio of time to solution of a …
73 questions
The Deutsch–Jozsa algorithm is a quantum algorithm, proposed by David Deutsch and Richard Jozsa in 1992. Although of little practical use, it is one of the first examples of a quantum algorithm that i…
67 questions
An oracle is a "black box" operation (function) that is used as an input to an another algorithm (for example Deutch-Jozsa, Grover etc.). A parameter or feature of the Oracle is infered by the algorit…
63 questions
For questions about quantum algorithms tackling machine learning tasks (e.g. the HHL algorithm or questions about quantum neural networks). For questions about applying classical machine learning to q…
61 questions
For questions about the superconducting realization of quantum computers. Questions can be about both the implementation of this realization or the theory behind this realization. If you are asking ab…
A quantum computing company, based in Burnaby, British Columbia, Canada, mostly known for their quantum annealing computers. An early rendition of these, D-Wave One, was the first commercially availab…
61 questions
For questions centred around or involving the notion of partial trace. The partial trace is a generalization of the notion of trace defined for multipartite systems.
60 questions
Quantum communication is a generalization of quantum cryptography. It refers to protocols and techniques for transmission of an unknown quantum state (of a quantum system) from one place to another.
58 questions
It is a metaheuristic for finding the global minimum of a given objective function over a given set of candidate solutions (candidate states), by a process using quantum fluctuations. (Wikipedia)
57 questions
For questions related to Bell basis - i.e. converting a state to the Bell basis, working with such states and measuring in the basis.
55 questions
For questions about quantum state tomography, that is, the process of fully characterizing a quantum state from experimental measurements.
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For questions relating to the Kraus decomposition of quantum channels.
53 questions
Quantum decoherence is the loss of quantum coherence. As long as there exists a definite phase relation between different states, the system is said to be coherent. This coherence is a fundamental pro…
52 questions
For questions related to experiments with actual quantum computing devices and how to interpret their results. Also appropriate if the question can only be reasonable answered with an experiment (or e…
51 questions
Adiabatic quantum computation (AQC) is a form of quantum computing which relies on the adiabatic theorem to do calculations and is closely related to and may be regarded as a subclass of, quantum anne…
50 questions
Quantum assembly language (QASM) called OpenQASM is used to implement experiments with low depth quantum circuits. OpenQASM represents universal physical circuits over the CNOT plus SU(2) basis with s…
50 questions
For questions regarding applications of quantum computing and quantum information theory in quantum chemistry or applications of chemistry in quantum computing architecture.
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