Function applyMatrix4

pub unsafe extern "C" fn applyMatrix4(
    qureg: Qureg,
    targetQubit1: c_int,
    targetQubit2: c_int,
    u: ComplexMatrix4,
)

Apply a general 4-by-4 matrix, which may be non-unitary. The matrix is left-multiplied onto the state, for both state-vectors and density matrices.

Note this differs from the action of twoQubitUnitary() on a density matrix.

\p targetQubit1 is treated as the \p least significant qubit in \p u, such that a row in \p u is dotted with the vector \f$ |\text{targetQubit2} ;; \text{targetQubit1}\rangle : { |00\rangle, |01\rangle, |10\rangle, |11\rangle } \f$

For example,

    applyMatrix4(qureg, a, b, u);

will invoke multiplication \f[ \begin{pmatrix} u_{00} & u_{01} & u_{02} & u_{03} \ u_{10} & u_{11} & u_{12} & u_{13} \ u_{20} & u_{21} & u_{22} & u_{23} \ u_{30} & u_{31} & u_{32} & u_{33} \end{pmatrix} \begin{pmatrix} |ba\rangle = |00\rangle \ |ba\rangle = |01\rangle \ |ba\rangle = |10\rangle \ |ba\rangle = |11\rangle \end{pmatrix} \f]

This function may leave \p qureg is an unnormalised state.

Note that in distributed mode, this routine requires that each node contains at least 4 amplitudes. This means an q-qubit register (state vector or density matrix) can be distributed by at most 2^q/4 nodes.

@see

• ::ComplexMatrix4
• twoQubitUnitary()

@ingroup operator @param[in,out] qureg object representing the set of all qubits @param[in] targetQubit1 first qubit to operate on, treated as least significant in \p u @param[in] targetQubit2 second qubit to operate on, treated as most significant in \p u @param[in] u matrix to apply @throws invalidQuESTInputError()

• if \p targetQubit1 or \p targetQubit2 are outside [0, \p qureg.numQubitsRepresented)
• if \p targetQubit1 equals \p targetQubit2
• if each node cannot fit 4 amplitudes in distributed mode @author Tyson Jones