cirq.ActOnDensityMatrixArgs

State and context for an operation acting on a density matrix.

Inherits From: ActOnArgs, OperationTarget

cirq.ActOnDensityMatrixArgs(
    target_tensor: Optional[np.ndarray] = None,
    available_buffer: Optional[List[np.ndarray]] = None,
    qid_shape: Optional[Tuple[int, ...]] = None,
    prng: Optional[np.random.RandomState] = None,
    log_of_measurement_results: Optional[Dict[str, List[int]]] = None,
    qubits: Optional[Sequence['cirq.Qid']] = None,
    ignore_measurement_results: bool = False,
    initial_state: Union[np.ndarray, 'cirq.STATE_VECTOR_LIKE'] = 0,
    dtype: Type[np.number] = np.complex64,
    classical_data: Optional['cirq.ClassicalDataStore'] = None
)

To act on this object, directly edit the target_tensor property, which is storing the density matrix of the quantum system with one axis per qubit.

target_tensor The state vector to act on, stored as a numpy array with one dimension for each qubit in the system. Operations are expected to perform inplace edits of this object.
available_buffer A workspace with the same shape and dtype as target_tensor. Used by operations that cannot be applied to target_tensor inline, in order to avoid unnecessary allocations.
qubits Determines the canonical ordering of the qubits. This is often used in specifying the initial state, i.e. the ordering of the computational basis states.
qid_shape The shape of the target tensor.
prng The pseudo random number generator to use for probabilistic effects.
log_of_measurement_results A mutable object that measurements are being recorded into.
ignore_measurement_results If True, then the simulation will treat measurement as dephasing instead of collapsing process. This is only applicable to simulators that can model dephasing.
initial_state The initial state for the simulation in the computational basis.
dtype The numpy.dtype of the inferred state vector. One of numpy.complex64 or numpy.complex128. Only used when target_tenson is None.
classical_data The shared classical data container for this simulation.

ValueError The dimension of target_tensor is not divisible by 2 and qid_shape is not provided.

allows_factoring Subclasses that allow factorization should override this.
available_buffer

can_represent_mixed_states

classical_data The shared classical data container for this simulation..
ignore_measurement_results

log_of_measurement_results Gets the log of measurement results.
prng

qid_shape

qubit_map

qubits Gets the qubit order maintained by this target.
target_tensor

Methods

apply_operation

View source

apply_operation(
    op: 'cirq.Operation'
)

copy

View source

copy(
    deep_copy_buffers: bool = True
) -> TSelf

Creates a copy of the object.

Args
deep_copy_buffers If True, buffers will also be deep-copied. Otherwise the copy will share a reference to the original object's buffers.

Returns
A copied instance.

create_merged_state

View source

create_merged_state() -> TSelf

Creates a final merged state.

factor

View source

factor(
    qubits: Sequence['cirq.Qid'], *, validate=True, atol=1e-07, inplace=False
) -> Tuple[TSelf, TSelf]

Splits two state spaces after a measurement or reset.

get_axes

View source

get_axes(
    qubits: Sequence['cirq.Qid']
) -> List[int]

kronecker_product

View source

kronecker_product(
    other: TSelf, *, inplace=False
) -> TSelf

Joins two state spaces together.

measure

View source

measure(
    qubits: Sequence['cirq.Qid'], key: str, invert_mask: Sequence[bool]
)

Measures the qubits and records to log_of_measurement_results.

Any bitmasks will be applied to the measurement record. If self._ignore_measurement_results is set, it dephases instead of measuring, and no measurement result will be logged.

Args
qubits The qubits to measure.
key The key the measurement result should be logged under. Note that operations should only store results under keys they have declared in a _measurement_key_names_ method.
invert_mask The invert mask for the measurement.

Raises
ValueError If a measurement key has already been logged to a key.

rename

View source

rename(
    q1: 'cirq.Qid', q2: 'cirq.Qid', *, inplace=False
)

Renames q1 to q2.

Args
q1 The qubit to rename.
q2 The new name.
inplace True to rename the qubit in the current object, False to create a copy with the qubit renamed.

Returns
The original object with the qubits renamed if inplace is requested, or a copy of the original object with the qubits renamed otherwise.

Raises
ValueError If the qubits are of different dimensionality.

sample

View source

sample(
    qubits: Sequence['cirq.Qid'],
    repetitions: int = 1,
    seed: 'cirq.RANDOM_STATE_OR_SEED_LIKE' = None
) -> np.ndarray

Samples the state value.

swap

View source

swap(
    q1: 'cirq.Qid', q2: 'cirq.Qid', *, inplace=False
)

Swaps two qubits.

This only affects the index, and does not modify the underlying state.

Args
q1 The first qubit to swap.
q2 The second qubit to swap.
inplace True to swap the qubits in the current object, False to create a copy with the qubits swapped.

Returns
The original object with the qubits swapped if inplace is requested, or a copy of the original object with the qubits swapped otherwise.

Raises
ValueError If the qubits are of different dimensionality.

transpose_to_qubit_order

View source

transpose_to_qubit_order(
    qubits: Sequence['cirq.Qid'], *, inplace=False
) -> TSelf

Physically reindexes the state by the new basis.

Args
qubits The desired qubit order.
inplace True to perform this operation inplace.

Returns
The state with qubit order transposed and underlying representation updated.

Raises
ValueError If the provided qubits do not match the existing ones.

with_qubits

View source

with_qubits(
    qubits
) -> TSelf

Extend current state space with added qubits.

The state of the added qubits is the default value set in the subclasses. A new state space is created as the Kronecker product of the original one and the added one.

Args
qubits The qubits to be added to the state space.

Regurns:

A new subclass object containing the extended state space.

__getitem__

View source

__getitem__(
    item: Optional['cirq.Qid']
) -> TSelf

Gets the item associated with the qubit.

__iter__

View source

__iter__() -> Iterator[Optional['cirq.Qid']]

Iterates the keys of the mapping.

__len__

View source

__len__() -> int

Gets the number of items in the mapping.