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DensityMatrix

class DensityMatrix(data, dims=None)[source]

Bases : QuantumState, TolerancesMixin

DensityMatrix class

Initialize a density matrix object.

Paramètres
  • or (data (np.ndarray or list or matrix_like or QuantumCircuit) – qiskit.circuit.Instruction): A statevector, quantum instruction or an object with a to_operator or to_matrix method from which the density matrix can be constructed. If a vector the density matrix is constructed as the projector of that vector. If a quantum instruction, the density matrix is constructed by assuming all qubits are initialized in the zero state.

  • dims (int or tuple or list) – Optional. The subsystem dimension of the state (See additional information).

Lève

QiskitError – if input data is not valid.

Additional Information:

The dims kwarg can be None, an integer, or an iterable of integers.

  • Iterable – the subsystem dimensions are the values in the list with the total number of subsystems given by the length of the list.

  • Int or None – the leading dimension of the input matrix specifies the total dimension of the density matrix. If it is a power of two the state will be initialized as an N-qubit state. If it is not a power of two the state will have a single d-dimensional subsystem.

Methods

conjugate

Return the conjugate of the density matrix.

copy

Make a copy of current operator.

dims

Return tuple of input dimension for specified subsystems.

draw

Return a visualization of the Statevector.

evolve

Evolve a quantum state by an operator.

expand

Return the tensor product state other ⊗ self.

expectation_value

Compute the expectation value of an operator.

from_instruction

Return the output density matrix of an instruction.

from_int

Return a computational basis state density matrix.

from_label

Return a tensor product of Pauli X,Y,Z eigenstates.

is_valid

Return True if trace 1 and positive semidefinite.

measure

Measure subsystems and return outcome and post-measure state.

probabilities

Return the subsystem measurement probability vector.

probabilities_dict

Return the subsystem measurement probability dictionary.

purity

Return the purity of the quantum state.

reset

Reset state or subsystems to the 0-state.

reverse_qargs

Return a DensityMatrix with reversed subsystem ordering.

sample_counts

Sample a dict of qubit measurement outcomes in the computational basis.

sample_memory

Sample a list of qubit measurement outcomes in the computational basis.

seed

Set the seed for the quantum state RNG.

tensor

Return the tensor product state self ⊗ other.

to_dict

Convert the density matrix to dictionary form.

to_operator

Convert to Operator

to_statevector

Return a statevector from a pure density matrix.

trace

Return the trace of the density matrix.

Attributes

atol = 1e-08
data

Return data.

dim

Return total state dimension.

num_qubits

Return the number of qubits if a N-qubit state or None otherwise.

rtol = 1e-05
settings

Return settings.