List of functions

This is a list of functions provided by QETLAB, arranged by category. If you would prefer an alphabetical list of all functions please see this page. Brief descriptions of these functions are provided here, as well as links to their documentation pages, where full details and numerous examples can be found.

Basic Operations

• IsPSD: Determines whether or not a matrix is positive semidefinite
• Tensor: Kronecker tensor product of two or more matrices
• TensorSum: Computes a vector or operator from its tensor decomposition

Entanglement and Separability

• IsEntanglingGate: Determines if a unitary is an entangling gate
• IsPPT: Determines whether or not a matrix has positive partial transpose
• IsProductOperator: Determines if an operator is an elementary tensor
• IsProductVector: Determines if a pure state is a product vector
• OperatorSchmidtDecomposition: Computes the operator Schmidt decomposition of a bipartite operator
• OperatorSchmidtRank: Computes the operator Schmidt rank of a bipartite operator
• SchmidtDecomposition: Computes the Schmidt decomposition of a bipartite vector
• SchmidtNumber: (coming soon)
• SchmidtRank: Computes the Schmidt rank of a bipartite vector
• SymmetricExtension: Determines whether or not an operator has a symmetric extension

Norms

• CBNorm: Computes the completely bounded norm of a superoperator
• DiamondNorm: Computes the diamond norm of a superoperator
• kpNorm: Computes the (k,p)-norm of an operator
• kpNormDual: Computes the dual of the (k,p)-norm of an operator
• KyFanNorm: Computes the Ky Fan k-norm of an operator
• SkOperatorNorm: Bounds the S(k)-norm of an operator
• SkVectorNorm: Computes the s(k)-norm of a vector
• SchattenNorm: Computes the Schatten p-norm of an operator
• TraceNorm: Computes the trace norm of an operator

Permutations and Symmetry of Subsystems

• AntisymmetricProjection: Produces the projection onto the antisymmetric subspace
• PermutationOperator: Produces a unitary operator that permutes subsystems
• PermuteSystems: Permutes subsystems within a state or operator
• Swap: Swaps two subsystems within a state or operator
• SwapOperator: Produces a unitary operator that swaps two subsystems
• SymmetricProjection: Produces the projection onto the symmetric subspace

Random Things

• RandomDensityMatrix: Generates a random density matrix
• RandomStateVector: Generates a random pure state vector
• RandomSuperoperator: (coming soon)
• RandomUnitary: Generates a random unitary or orthogonal matrix

Special States, Vectors, and Operators

• FourierMatrix: Generates the unitary matrix that implements the quantum Fourier transform
• IsotropicState: Produces an isotropic state
• MaxEntangled: Produces a maximally entangled bipartite pure state
• WernerState: Produces a Werner state

Superoperators

• ApplyMap: Applies a superoperator to an operator
• ChoiMatrix: Computes the Choi matrix of a superoperator
• IsCP: Determines whether or not a superoperator is completely positive
• IsHermPreserving: Determines whether or not a superoperator is Hermiticity preserving
• PartialMap: Applies a superoperator to a subsystem of an operator
• PartialTrace: Computes the partial trace of a matrix
• PartialTranspose: Computes the partial transpose of a matrix
• Realignment: Computes the realignment of a bipartite operator

Miscellaneous

• Commutant: Computes the commutant of a set of matrices
• IsTotallyNonsingular: Determines whether or not a matrix is totally nonsingular
• IsTotallyPositive: Determines whether or not a matrix is totally positive

Helper Functions

• iden: Computes a sparse or full identity matrix
• kron: A faster version of MATLAB's kron function
• normalize_cols: Scales the columns of a matrix to have norm 1
• opt_args: Handles optional input arguments for functions
• opt_disp: Display a message to the user (sometimes)
• perm_inv: Computes the inverse of a permutation
• perm_sign: Computes the sign of a permutation
• spnull: Returns a sparse orthonormal basis for the null space
• sporth: Returns a sparse orthonormal basis for the range