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sf.ops.Vacuum

class Vacuum[source]

Bases: strawberryfields.ops.Preparation

Prepare a mode in the vacuum state.

Can be accessed via the shortcut variable Vac.

Note

By default, newly created modes in Strawberry Fields default to the vacuum state.

Definition

The vacuum state \(\ket{0}\) is a Gaussian state defined by

\[\ket{0} = \frac{1}{\sqrt[4]{\pi \hbar}} \int dx~e^{-x^2/(2 \hbar)}\ket{x} ~~\text{where}~~ \a\ket{0}=0\]

Tip

Available in Strawberry Fields as a NumPy array by strawberryfields.utils.vacuum_state()

In the Fock basis, it is represented by Fock state \(\ket{0}\), and in the Gaussian formulation, by \(\bar{\mathbf{r}}=(0,0)\) and \(\mathbf{V}= \frac{\hbar}{2} I\).

measurement_deps

Extra dependencies due to parameters that depend on measurements.

ns

measurement_deps

Extra dependencies due to parameters that depend on measurements.

Returns

dependencies

Return type

set[RegRef]

ns = 1

apply(reg, backend, **kwargs)

Ask a local backend to execute the operation on the current register state right away.

decompose(reg, **kwargs)

Decompose the operation into elementary operations supported by the backend API.

merge(other)

Merge the operation with another (acting on the exact same set of subsystems).
apply(reg, backend, **kwargs)

Ask a local backend to execute the operation on the current register state right away.

Takes care of parameter evaluations and any pending formal transformations (like dagger) and then calls Operation._apply().

Parameters

  • reg (Sequence[RegRef]) – subsystem(s) the operation is acting on

  • backend (BaseBackend) – backend to execute the operation

Returns

the result of self._apply

Return type

Any

decompose(reg, **kwargs)

Decompose the operation into elementary operations supported by the backend API.

See strawberryfields.backends.base.

Parameters

reg (Sequence[RegRef]) – subsystems the operation is acting on

Returns

decomposition as a list of operations acting on specific subsystems

Return type

list[Command]

merge(other)

Merge the operation with another (acting on the exact same set of subsystems).

Note

For subclass overrides: merge may return a newly created object, or self, or other, but it must never modify self or other because the same Operation objects may be also used elsewhere.

Parameters

other (Operation) – operation to merge this one with

Returns

other * self. The return value None represents the identity gate (doing nothing).

Return type

Operation, None

Raises

MergeFailure – if the two operations cannot be merged

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