Every algorithm in the catalogue, written on this page — not behind a call. Each description is the sealed Quantum Algorithm Zoo snapshot; what Rosetta measured, and where, lives in the ledger.
Oracular Algorithms · 31
Find a hidden subgroup of a commutative group by querying a function that is constant on each coset. This is the shared pattern behind Shor: factoring, discrete log and Pell all reduce to it.
Superpolynomial · 6 refs
Recover a secret string hidden inside a linear function with as few queries as possible.
Polynomial Directly, Superpolynomial Recursively · 5 refs
Locate the centre of a radially symmetric function by querying it pointwise.
Polynomial · 1 refs
Find two inputs with the same output, or decide whether all elements of a list are distinct.
Polynomial · 14 refs
Identify fake coins in as few weighings as possible: the classic puzzle, in query form.
Polynomial · 2 refs
Decide whether a boolean function is constant or balanced in a single query. The first historical separation between quantum and classical.
Exponential over P, none over BPP · 3 refs
Compute the effective resistance between two nodes of a graph whose edge weights are read as resistances.
Exponential · 3 refs
Compute the structure of finite rings and of their ideals.
Superpolynomial · 3 refs
Evaluate the value of a boolean formula (AND/OR/NOT) with oracle access to its inputs.
Polynomial · 13 refs
Decide whether some pair of adjacent vertices is labelled 1, given oracle access to the labelling.
Polynomial · 5 refs
The same, but reaching the graph through neighbour lists: the model changes the cost.
Polynomial · 3 refs
Decide graph properties (connectivity, bipartiteness, cycles) by querying the adjacency matrix.
Polynomial · 21 refs
Decide whether a group given by its generators is commutative.
Polynomial · 1 refs
Decide whether two finite groups given by oracle and generators are the same group under different names.
Superpolynomial · 3 refs
Compute the order of a group and decide whether an element belongs to it.
Superpolynomial · 3 refs
Find hidden structures that are not subgroups but nonlinear objects such as spheres or cones.
Superpolynomial · 3 refs
Given two functions that differ by an unknown shift, find that shift.
Superpolynomial · 12 refs
Decide whether a function depends on at most k of its n input bits. Closely related to group testing.
Polynomial · 4 refs
Decide whether a set of matrices commutes.
Polynomial · 1 refs
Multiply matrices over semirings (min-plus, for instance), the core of several shortest-path problems.
Polynomial · 5 refs
Compute the rank of a matrix with oracle access to its entries.
Polynomial · 3 refs
Compute maximum flow, or minimum-cost flow, on a network with capacities on its edges.
Polynomial · 1 refs
The same problem over non-commutative groups. Solving it in general would attack graph isomorphism and lattices, and it remains open.
Superpolynomial · 24 refs
Search a sorted list. The quantum margin here is only a constant factor, not a change of order.
Constant factor · 5 refs
Locate a pattern inside a long text.
Superpolynomial · 5 refs
Reconstruct a polynomial's coefficients by querying it at points.
Varies · 7 refs
Recover a hidden string when queries may leave positions unspecified.
Polynomial · 1 refs
Find the needle in an unstructured haystack: locate a marked item among N with only a yes/no oracle. This is Grover.
Polynomial · 32 refs
Estimate how far apart two probability distributions are, with sampling access only.
Polynomial · 3 refs
Find a k-element subset satisfying a given property.
Polynomial · 3 refs
Traverse two binary trees welded at the leaves. The clean example of exponential separation by quantum walk.
Superpolynomial · 1 refs
Optimization, Numerics, and Machine Learning · 18
Solve a problem by starting from an easy Hamiltonian and deforming it slowly into one whose ground state encodes the answer. The model behind quantum annealing.
A plausible example of superpolynomial speedup appears in [ 530 ] · 34 refs
Approximate Nash equilibria in two-player games.
Polynomial · 2 refs
Compute the principal eigenvector of a matrix, the core of PageRank-style methods.
Polynomial · 1 refs
Optimise over convex bodies and estimate their volumes, with membership-oracle access to the body.
Polynomial · 11 refs
A family based on double-bracket flows for diagonalising and preparing states. The source declares its advantage unknown.
Unknown · 6 refs
Estimate determinants, traces and other sums over a matrix's spectrum.
Superpolynomial · 2 refs
Estimate the gradient of a smooth function at a point, or learn a polynomial's coefficients, by querying an oracle.
Polynomial · 8 refs
Attack lattice problems, which are the basis of the post-quantum cryptography standardised by NIST.
Exponential · 3 refs
Solve Ax = b. This is HHL, and the asterisk matters: it returns a quantum state encoding the solution, not the answer vector.
Superpolynomial · 24 refs
Umbrella entry gathering the quantum techniques proposed for machine learning. Also the area where the most claims fell to dequantization — classical algorithms that later matched the supposed advantage.
Varies · 56 refs
Reduce certain optimisation problems to a decoding problem, and solve that instead.
Superpolynomial · 13 refs
Solve constraint satisfaction problems (SAT and family) with a polynomial improvement over the best classical backtracking.
Polynomial · 8 refs
Search for good approximate solutions to combinatorial problems with a short parameterised circuit. This is QAOA, and it is the family carrying almost the entire commercial promise of quantum optimisation.
Superpolynomial · 12 refs
Solve path-in-the-hypercube problems by dynamic programming, a family that includes the travelling salesman.
Polynomial · 1 refs
Optimise a linear objective over positive semidefinite matrices under linear constraints. The workhorse of convex relaxation.
Polynomial (with some exceptions) · 6 refs
Solve systems of linear differential equations.
Superpolynomial · 19 refs
Solve nonlinear differential equations, under strong assumptions about how nonlinear they may be.
Superpolynomial · 13 refs
Recover a signal hidden inside a high-dimensional tensor of Gaussian noise.
Polynomial (quartic) · 1 refs
Algebraic and Number Theoretic Algorithms · 14
Compute the class group of a number field, a central invariant of algebraic number theory.
Superpolynomial · 2 refs
Decode a linear error-correcting code, the hard problem that code-based cryptography rests on.
Varies · 2 refs
Given b = a^s mod N, find s. Underpins DSA, ECDSA and Diffie-Hellman key exchange.
Superpolynomial · 7 refs
Break an n-bit integer into its prime factors. This is what RSA rests on.
Superpolynomial · 13 refs
Estimate Gauss sums over finite fields, a basic object of number theory.
Superpolynomial · 2 refs
Estimate matrix elements and multiplicity coefficients of group representations, including Clebsch-Gordan coefficients.
Superpolynomial · 6 refs
Solve Pell's equation x^2 - d*y^2 = 1 over the integers. Breaking it breaks the Buchmann-Williams cryptosystem.
Superpolynomial · 1 refs
Certify that a number is prime, not merely probably prime.
Polynomial · 7 refs
Decide whether an ideal of a number field is principal and, if so, find its generator. At least as hard as factoring.
Superpolynomial · 3 refs
Attack specific cryptographic primitives with quantum resources, beyond Shor and Grover.
Various · 23 refs
Solve congruences whose unknowns sit in the exponent.
Polynomial · 1 refs
Given a set of numbers, find a subset that adds up to a target value.
Polynomial · 3 refs
Compute the unit group of the ring of integers of a number field.
Superpolynomial · 4 refs
Check whether the product of two matrices equals a third, faster than multiplying them.
Polynomial · 3 refs
Approximation and Simulation Algorithms · 11
Approximate the Jones polynomial and other knot invariants, a BQP-hard problem.
Superpolynomial · 10 refs
Estimate entries of high powers of a matrix without computing the full matrix.
Superpolynomial · 1 refs
Estimate the partition function of a classical system, from which essentially every thermodynamic quantity follows.
Superpolynomial · 10 refs
Prepare the ground state or a thermal state of a Hamiltonian, the starting point of almost all materials and chemistry simulation.
Superpolynomial · 31 refs
Sample from distributions a classical computer cannot sample efficiently.
Superpolynomial · 3 refs
Speed up simulated annealing: reach the equilibrium of a Markov chain in fewer steps.
Polynomial · 5 refs
Simulate how a quantum system evolves in time given its Hamiltonian. Feynman's original application and the strongest candidate for real utility.
Superpolynomial · 61 refs
Decide word problems in string-rewriting systems.
Superpolynomial · 2 refs
Approximate topological invariants of three-dimensional manifolds.
Superpolynomial · 3 refs
Compute weight enumerators of codes, which describe the distance distribution of an error-correcting code.
Superpolynomial · 4 refs
Compute zeta functions of curves over finite fields, with direct use in elliptic-curve cryptography.
Superpolynomial · 2 refs