Preparations#

class Vacuum#

Prepare the system in a vacuum state.

Example usage:

with pq.Program() as program:
    pq.Q() | pq.Vacuum()
    ...

Note

This operation can only be used for all modes and is only practical to be used at the beginning of a program declaration.

class Mean(mean: ndarray)#

Set the first canonical moment of the state.

Example usage:

with pq.Program() as program:
    pq.Q() | pq.Mean(
        mean=np.array(...)
    )
    ...

Can only be applied to the following states: GaussianState.

Note

The mean vector is dependent on \(\hbar\), but the value of \(\hbar\) is specified later when executed by a simulator. The parameter mean should be specified keeping in mind that it will automatically be scaled with \(\hbar\) during execution.

Parameters:: mean (numpy.ndarray) – The vector of the first canonical moments in xpxp-ordering.

class Covariance(cov: ndarray)#

Sets the covariance matrix of the state.

Example usage:

with pq.Program() as program:
    pq.Q() | pq.Covariance(
        cov=np.array(...)
    )
    ...

Can only be applied to the following states: GaussianState.

Note

The covariance matrix is dependent on \(\hbar\), but the value of \(\hbar\) is specified later when executed by a simulator. The parameter cov should be specified keeping in mind that it will automatically be scaled with \(\hbar\) during execution.

Parameters:: cov (numpy.ndarray) – The covariance matrix in xpxp-ordering.

class Thermal(mean_photon_numbers: Iterable[float])#

Prepares a thermal state.

Example usage:

with pq.Program() as program:
    pq.Q(0, 1) | pq.Thermal([0.5, 1.5])
    ...

The thermal state is defined by

\[\rho = \sum_{\vec{n} = 0}^\infty \frac{\overline{n}^{\vec{n}}}{(1 + \overline{n})^{\vec{n} + 1}} | \vec{n} \rangle \langle \vec{n} |,\]

where \(\overline{n} \in \mathbb{R}^d\) is the vector of mean photon numbers. The power on vectors is defined as

\[\vec{a}^{\vec{b}} = \prod_{i=1}^d a_i^{b_i}\]

In terms of Gaussian states, the mean vector and covariance matrix is

\[\begin{split}\mu &= 0_{2d} \\ \sigma &= \hbar ( 2 \operatorname{\textit{diag}}(\operatorname{\textit{repeat}} (\overline{n}, 2)) + I_{2d \times 2d} )\end{split}\]

Can only be applied to the following states: GaussianState.

Parameters:: mean_photon_numbers (Iterable[float]) – The sequence of mean photon numbers.
Raises:: InvalidParameter – If the mean photon numbers are not positive real numbers.

class StateVector(occupation_numbers: Iterable[int], coefficient: complex = 1.0)#

State preparation with Fock basis vectors.

Example usage:

with pq.Program() as program:
    pq.Q() | (
        0.3 * pq.StateVector([2, 1, 0, 3])
        + 0.2 * pq.StateVector([1, 1, 2, 3])
        ...
    )
    ...

Can only be applied to the following states: PureFockState.

Parameters:

occupation_numbers (Iterable[int]) – The occupation numbers.
coefficient (complex, optional) – The coefficient of the occupation number. Defaults to \(1.0\).

Raises:

InvalidState – If the specified occupation numbers are not all natural numbers.

class DensityMatrix(ket: Iterable[int], bra: Iterable[int], coefficient: complex = 1.0)#

State preparation with density matrix elements.

Example usage:

with pq.Program() as program:
    pq.Q() | (
        0.2 * pq.DensityMatrix(ket=(1, 0, 1), bra=(2, 1, 0))
        + 0.3 * pq.DensityMatrix(ket=(2, 0, 1), bra=(0, 1, 1))
        ...
    )
    ...

Note

This only creates one matrix element.

Can only be applied to the following states: FockState.

Parameters:

bra (Iterable[int]) – The bra vector.
ket (Iterable[int]) – The ket vector.
coefficient (complex, optional) – The coefficient of the operator defined by the “bra” and “ket” vectors. Defaults to \(1.0\).

Raises:

InvalidState – If the specified “bra” or “ket” vectors are not all natural numbers.

class Create#

Create a particle on a mode.

This instruction essentially applies a creation operator on the specified mode, then normalizes the state.

Example usage:

with pq.Program() as program:
    pq.Q(1) | pq.Create()
    pq.Q(2) | pq.Create()
    ...

Can only be applied to the following states: FockState, PureFockState.

class Annihilate#

Annihilate a particle on a mode.

This instruction essentially applies an annihilation operator on the specified mode, then normalizes the state.

Example usage:

with pq.Program() as program:
    ...
    pq.Q(0) | pq.Annihilate()
    ...

Can only be applied to the following states: FockState, PureFockState.