# sf.circuitspecs.GBSSpecs¶

class GBSSpecs[source]

Bases: strawberryfields.circuitspecs.gaussian.GaussianSpecs

Circuit specifications for the general GBS class of circuits.

 circuit A rigid circuit template that defines this circuit specification. decompositions graph The allowed circuit topologies or connectivity of the class, modelled as a directed acyclic graph. interactive local modes parameter_ranges Allowed parameter ranges for supported quantum operations. primitives remote short_name
circuit

A rigid circuit template that defines this circuit specification.

This property is optional. If arbitrary topologies are allowed in the circuit class, do not define this property. In such a case, it will simply return None.

If a backend device expects a specific template for the recieved Blackbird script, this method will return the serialized Blackbird circuit in string form.

Returns

Blackbird program or template representing the circuit

Return type

Union[str, None]

decompositions = {'Fouriergate': {}, 'S2gate': {}, 'Xgate': {}, 'Zgate': {}}
graph

The allowed circuit topologies or connectivity of the class, modelled as a directed acyclic graph.

This property is optional; if arbitrary topologies are allowed in the circuit class, this will simply return None.

Returns

a directed acyclic graph

Return type

networkx.DiGraph

interactive = True
local = True
modes = None
parameter_ranges

Allowed parameter ranges for supported quantum operations.

This property is optional.

Returns

a dictionary mapping an allowed quantum operation to a nested list of the form [[p0_min, p0_max], [p1_min, p0_max], ...]. where pi corresponds to the i th gate parameter

Return type

dict[str, list]

primitives = {'All', 'BSgate', 'Coherent', 'Dgate', 'DisplacedSqueezed', 'Fouriergate', 'Gaussian', 'LossChannel', 'MeasureFock', 'MeasureHeterodyne', 'MeasureHomodyne', 'MeasureThreshold', 'Rgate', 'Sgate', 'Squeezed', 'Thermal', 'ThermalLossChannel', 'Vacuum', '_Delete', '_New_modes'}
remote = True
short_name = 'gbs'
 compile(seq, registers) Try to arrange a quantum circuit into a form suitable for Gaussian boson sampling. decompose(seq) Recursively decompose all gates in a given sequence, as allowed by the circuit specification.
compile(seq, registers)[source]

Try to arrange a quantum circuit into a form suitable for Gaussian boson sampling.

This method checks whether the circuit can be implemented as a Gaussian boson sampling problem, i.e., if it is equivalent to a circuit A+B, where the sequence A only contains Gaussian operations, and B only contains Fock measurements.

If the answer is yes, the circuit is arranged into the A+B order, and all the Fock measurements are combined into a single MeasureFock operation.

Parameters
• seq (Sequence[Command]) – quantum circuit to modify

• registers (Sequence[RegRefs]) – quantum registers

Returns

modified circuit

Return type

List[Command]

Raises

CircuitError – the circuit does not correspond to GBS

decompose(seq)

Recursively decompose all gates in a given sequence, as allowed by the circuit specification.

This method follows the directives defined in the primitives and decompositions class attributes to determine whether a command should be decomposed.

The order of precedence to determine whether decomposition should be applied is as follows.

1. First, we check if the operation is in decompositions. If not, decomposition is skipped, and the operation is applied as a primitive (if supported by the CircuitSpecs).

2. Next, we check if (a) the operation supports decomposition, and (b) if the user has explicitly requested no decomposition.

• If both (a) and (b) are true, the operation is applied as a primitive (if supported by the CircuitSpecs).

• Otherwise, we attempt to decompose the operation by calling decompose() recursively.

Parameters

list[strawberryfields.program_utils.Command] – list of commands to be decomposed

Returns

list of compiled commands for the circuit specification

Return type