Density matrix utility functions for simulator

numqi.sim.dm

numqi.sim.dm.new_base(num_qubit, dtype=np.complex128)

return the base density matrix of the qubit quantum system

Parameters:

Name	Type	Description	Default
num_qubit	int	the number of qubits	required
dtype	dtype	the data type of the base state	complex128

Returns:

Name	Type	Description
ret	ndarray	the base state, ret.shape==(2**num_qubit,2**num_qubit)

numqi.sim.dm.apply_gate(dm, op, index)

apply a gate to the density matrix

Parameters:

Name	Type	Description	Default
dm	ndarray	the density matrix, dm.shape==(2**num_qubit,2**num_qubit)	required
op	ndarray	the gate, op.shape==(2**N0,2**N0)	required
index	int | tuple[int]	the qubit index to apply the gate, 0<=index<num_qubit, count from left to right |0123>	required

Returns:

Name	Type	Description
ret	ndarray	the density matrix after applying the gate

numqi.sim.dm.operator_expectation(dm0, op, index)

calculate the expectation value of an operator

TODO multiple operators

Parameters:

Name	Type	Description	Default
dm0	ndarray	the density matrix, dm0.shape==(2**num_qubit,2**num_qubit)	required
op	ndarray	the operator, op.shape==(2**N0,2**N0)	required
index	int | tuple[int]	the qubit index to apply the operator	required

Returns:

Name	Type	Description
ret	ndarray	the expectation value