Class qOperator#

Class Documentation#

class qOperator#

Represents a quantum operator in a block-diagonal form.

This class provides methods to manipulate and display quantum operators used in the NRG calculations.

Public Functions

qOperator() = default#

Default constructor creates an empty block-operator.

inline qOperator(qmatrix<double> &opr, size_t i, size_t j)#

Construct a block operator with an initial block entry.

This constructor stores a single block opr at block coordinates (i,j) and supports move semantics for efficient block initialization.

Parameters:

  • opr – The block matrix to insert.

  • i – Block row index.

  • j – Block column index.

inline auto getMap()#

Get the internal Storage object of the qmatrix

Returns:

std::map<std::array<size_t, 2>, qmatrix<>>

inline void set(const qmatrix<double> &opr, size_t i, size_t j)#

Set a block entry in the symmetry-basis operator.

Parameters:

  • opr – Matrix object stored in the (i, j) block.

  • i – Row block index in the symmetry basis.

  • j – Column block index in the symmetry basis.

inline void set(qmatrix<double> &opr, size_t i, size_t j)#

Set a block entry by moving a matrix into storage.

Parameters:

  • opr – Matrix object to move into the (i, j) block.

  • i – Row block index in the symmetry basis.

  • j – Column block index in the symmetry basis.

inline std::optional<qmatrix<double>*> get(size_t i, size_t j)#

This function returns the qmatrix pointer for the sub-block i and j. If the sub-block is not found, it returns an empty std::optional.

Parameters:

  • i – The index of the block to be returned.

  • j – The index of the block to be returned.

Returns:

std::optional<qmatrix>

inline void unitaryTransform(qOperator &U)#

Unitarily transform this operator with a block-diagonal matrix.

The U matrix is a block-diagonal qmatrix and the operator is updated as \(U^\dagger qOperator U\).

Parameters:

U – The unitary matrix to transform the qOperator. Usually we get this matrix after diagonalization of the Hamiltonian.

inline void clear()#

Clears the storage for the operator.

This method removes all stored matrix elements and resets the operator.

inline void display(std::ostream &out) const#

Prints the qOperator to the output stream.

Avoid calling this function if the size of the qOperator is large.

Parameters:

out – Output stream to print to.

Friends

inline friend std::ostream &operator<<(std::ostream &out, const qOperator &val)#

Overloads the stream insertion operator for qOperator.

Allows the use of std::cout << qOperator or any other ostream object.

Parameters:

  • out – The output stream.

  • val – The qOperator to print.

Returns:

The modified output stream.