cirq.BaseDensePauliString

Parent class for cirq.DensePauliString and cirq.MutableDensePauliString.

Inherits From: Gate

cirq.BaseDensePauliString(
    pauli_mask: (Iterable[cirq.PAULI_GATE_LIKE] | np.ndarray),
    *,
    coefficient: cirq.TParamValComplex = 1
)

cirq.BaseDensePauliString is an abstract base class, which is used to implement cirq.DensePauliString and cirq.MutableDensePauliString. The non-mutable version is used as the corresponding gate for cirq.PauliString operation and the mutable version is mainly used for efficiently manipulating dense pauli strings.

See the docstrings of cirq.DensePauliString and cirq.MutableDensePauliString for more details.

Examples:

print(cirq.DensePauliString('XXIY'))
+XXIY
 
print(cirq.MutableDensePauliString('IZII', coefficient=-1))
-IZII (mutable)
 
print(cirq.DensePauliString([0, 1, 2, 3],
                            coefficient=sympy.Symbol('t')))
t*IXYZ

pauli_mask A specification of the Pauli gates to use. This argument can be a string like "IXYYZ", or a numeric list like [0, 1, 3, 2] with I=0, X=1, Y=2, Z=3=X|Y.

The internal representation is a 1-dimensional uint8 numpy array containing numeric values. If such a numpy array is given, and the pauli string is mutable, the argument will be used directly instead of being copied.

coefficient A complex number. Usually +1, -1, 1j, or -1j but other values are supported.

coefficient A complex coefficient or symbol.
pauli_mask A 1-dimensional uint8 numpy array giving a specification of Pauli gates to use.

Methods

controlled

View source

controlled(
    num_controls: (int | None) = None,
    control_values: (cv.AbstractControlValues | Sequence[int | Collection[int]] | None) = None,
    control_qid_shape: (tuple[int, ...] | None) = None
) -> Gate

Returns a controlled version of this gate. If no arguments are specified, defaults to a single qubit control.

Args
num_controls Total number of control qubits.
control_values Which control computational basis state to apply the sub gate. A sequence of length num_controls where each entry is an integer (or set of integers) corresponding to the computational basis state (or set of possible values) where that control is enabled. When all controls are enabled, the sub gate is applied. If unspecified, control values default to 1.
control_qid_shape The qid shape of the controls. A tuple of the expected dimension of each control qid. Defaults to (2,) * num_controls. Specify this argument when using qudits.

Returns
A cirq.Gate representing self controlled by the given control values and qubits. This is a cirq.ControlledGate in the base implementation, but subclasses may return a different gate type.

copy

View source

@abc.abstractmethod
copy(
    coefficient: (cirq.TParamValComplex | None) = None,
    pauli_mask: (None | str | Iterable[int] | np.ndarray) = None
) -> Self

Returns a copy with possibly modified contents.

Args
coefficient The new coefficient value. If not specified, defaults to the current coefficient value.
pauli_mask The new pauli_mask value. If not specified, defaults to the current pauli mask value.

Returns
A copied instance.

eye

View source

@classmethod
eye(
    length: int
) -> Self

Creates a dense pauli string containing only identity gates.

Args
length The length of the dense pauli string.

frozen

View source

frozen() -> DensePauliString

A cirq.DensePauliString with the same contents.

mutable_copy

View source

mutable_copy() -> MutableDensePauliString

A cirq.MutableDensePauliString with the same contents.

num_qubits

View source

num_qubits() -> int

The number of qubits this gate acts on.

on

View source

on(
    *qubits
) -> cirq.PauliString

Returns an application of this gate to the given qubits.

Args
*qubits The collection of qubits to potentially apply the gate to.

Returns: a cirq.Operation which is this gate applied to the given qubits.

on_each

View source

on_each(
    *targets
) -> list[cirq.Operation]

Returns a list of operations applying the gate to all targets.

Args
*targets The qubits to apply this gate to. For single-qubit gates this can be provided as varargs or a combination of nested iterables. For multi-qubit gates this must be provided as an Iterable[Sequence[Qid]], where each sequence has num_qubits qubits.

Returns
Operations applying this gate to the target qubits.

Raises
ValueError If targets are not instances of Qid or Iterable[Qid]. If the gate qubit number is incompatible.
TypeError If a single target is supplied and it is not iterable.

one_hot

View source

@classmethod
one_hot(
    *, index: int, length: int, pauli: cirq.PAULI_GATE_LIKE
) -> Self

Creates a dense pauli string with only one non-identity Pauli.

Args
index The index of the Pauli that is not an identity.
length The total length of the string to create.
pauli The pauli gate to put at the hot index. Can be set to either a string ('X', 'Y', 'Z', 'I'), a cirq gate (cirq.X, cirq.Y, cirq.Z, or cirq.I), or an integer (0=I, 1=X, 2=Y, 3=Z).

sparse

View source

sparse(
    qubits: (Sequence[cirq.Qid] | None) = None
) -> cirq.PauliString

A cirq.PauliString version of this dense pauli string.

Args
qubits The qubits to apply the Paulis to. Defaults to cirq.LineQubit.range(len(self)).

Returns
A cirq.PauliString with the non-identity operations from this dense pauli string applied to appropriate qubits.

Raises
ValueError If the number of qubits supplied does not match that of this instance.

tensor_product

View source

tensor_product(
    other: BaseDensePauliString
) -> Self

Concatenates dense pauli strings and multiplies their coefficients.

Args
other The dense pauli string to place after the end of this one.

Returns
A dense pauli string with the concatenation of the paulis from the two input pauli strings, and the product of their coefficients.

validate_args

View source

validate_args(
    qubits: Sequence[cirq.Qid]
) -> None

Checks if this gate can be applied to the given qubits.

By default checks that:

  • inputs are of type Qid
  • len(qubits) == num_qubits()
  • qubit_i.dimension == qid_shape[i] for all qubits

Child classes can override. The child implementation should call super().validate_args(qubits) then do custom checks.

Args
qubits The sequence of qubits to potentially apply the gate to.

Raises
ValueError The gate can't be applied to the qubits.

with_probability

View source

with_probability(
    probability: cirq.TParamVal
) -> cirq.Gate

Creates a probabilistic channel with this gate.

Args
probability floating point value between 0 and 1, giving the probability this gate is applied.

Returns
cirq.RandomGateChannel that applies self with probability probability and the identity with probability 1-p.

wrap_in_linear_combination

View source

wrap_in_linear_combination(
    coefficient: cirq.TParamValComplex = 1
) -> cirq.LinearCombinationOfGates

Returns a LinearCombinationOfGates with this gate.

Args
coefficient number coefficient to use in the resulting cirq.LinearCombinationOfGates object.

Returns
cirq.LinearCombinationOfGates containing self with a coefficient of coefficient.

__abs__

View source

__abs__() -> Self

__add__

View source

__add__(
    other: (Gate | cirq.LinearCombinationOfGates)
) -> cirq.LinearCombinationOfGates

__call__

View source

__call__(
    *qubits, **kwargs
)

Call self as a function.

__eq__

View source

__eq__(
    other: _SupportsValueEquality
) -> bool

__getitem__

View source

__getitem__(
    item
)

__iter__

View source

__iter__() -> Iterator[cirq.Pauli | cirq.IdentityGate]

__len__

View source

__len__() -> int

__mul__

View source

__mul__(
    other
)

__ne__

View source

__ne__(
    other: _SupportsValueEquality
) -> bool

__neg__

View source

__neg__()

__pos__

View source

__pos__()

__pow__

View source

__pow__(
    power: float
) -> (NotImplementedType | Self)

__rmul__

View source

__rmul__(
    other
)

__sub__

View source

__sub__(
    other: (Gate | cirq.LinearCombinationOfGates)
) -> cirq.LinearCombinationOfGates

__truediv__

View source

__truediv__(
    other
)

I_VAL 0
X_VAL 1
Y_VAL 2
Z_VAL 3