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cirq.sim.StateVectorSimulationState

State and context for an operation acting on a state vector.

Inherits From: SimulationState, SimulationStateBase

There are two common ways to act on this object:

  1. Directly edit the target_tensor property, which is storing the state vector of the quantum system as a numpy array with one axis per qudit.
  2. Overwrite the available_buffer property with the new state vector, and then pass available_buffer into swap_target_tensor_for.

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. Passing available_buffer into swap_target_tensor_for will swap it for target_tensor.
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.
prng The pseudo random number generator to use for probabilistic effects.
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.

allows_factoring Subclasses that allow factorization should override this.
available_buffer

can_represent_mixed_states

classical_data

ignore_measurement_results THIS FUNCTION IS DEPRECATED.

IT WILL BE REMOVED IN cirq v0.16.

Remove this call, it always returns False.

log_of_measurement_results Gets the log of measurement results.
prng

qubit_map

qubits

target_tensor

Methods

apply_operation

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copy

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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

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Creates a final merged state.

factor

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Splits two state spaces after a measurement or reset.

get_axes

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kronecker_product

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Joins two state spaces together.

measure

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Measures the qubits and records to log_of_measurement_results.

Any bitmasks will be applied to the measurement record.

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

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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

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Samples the state value.

subspace_index

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THIS FUNCTION IS DEPRECATED.

IT WILL BE REMOVED IN cirq v0.16.

None, this function was unintentionally made public.

An index for the subspace where the target axes equal a value.

    Args:
        axes: The qubits that are specified by the index bits.
        little_endian_bits_int: The desired value of the qubits at the
            targeted `axes`, packed into an integer. The least significant
            bit of the integer is the desired bit for the first axis, and
            so forth in increasing order. Can't be specified at the same
            time as `big_endian_bits_int`.

            When operating on qudits instead of qubits, the same basic logic
            applies but in a different basis. For example, if the target
            axes have dimension [a:2, b:3, c:2] then the integer 10
            decomposes into [a=0, b=2, c=1] via 7 = 1*(3*2) +  2*(2) + 0.
        big_endian_bits_int: The desired value of the qubits at the
            targeted `axes`, packed into an integer. The most significant
            bit of the integer is the desired bit for the first axis, and
            so forth in decreasing order. Can't be specified at the same
            time as `little_endian_bits_int`.

            When operating on qudits instead of qubits, the same basic logic
            applies but in a different basis. For example, if the target
            axes have dimension [a:2, b:3, c:2] then the integer 10
            decomposes into [a=1, b=2, c=0] via 7 = 1*(3*2) +  2*(2) + 0.

    Returns:
        A value that can be used to index into `target_tensor` and
        `available_buffer`, and manipulate only the part of Hilbert space
        corresponding to a given bit assignment.

    Example:
        If `target_tensor` is a 4 qubit tensor and `axes` is `[1, 3]` and
        then this method will return the following when given
        `little_endian_bits=0b01`:

            `(slice(None), 0, slice(None), 1, Ellipsis)`

        Therefore the following two lines would be equivalent:

            args.target_tensor[args.subspace_index(0b01)] += 1

            args.target_tensor[:, 0, :, 1] += 1

swap

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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.

swap_target_tensor_for

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THIS FUNCTION IS DEPRECATED.

IT WILL BE REMOVED IN cirq v0.16.

None, this function was unintentionally made public.

Gives a new state vector for the system.

    Typically, the new state vector should be `args.available_buffer` where
    `args` is this <a href="../../cirq/sim/StateVectorSimulationState"><code>cirq.StateVectorSimulationState</code></a> instance.

    Args:
        new_target_tensor: The new system state. Must have the same shape
            and dtype as the old system state.

transpose_to_qubit_order

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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

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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__

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Gets the item associated with the qubit.

__iter__

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Iterates the keys of the mapping.

__len__

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Gets the number of items in the mapping.