sf.compilers.Compiler

class Compiler

Bases: abc.ABC

Abstract base class for describing circuit compilation.

This class stores information about compilation of photonic quantum circuits.

Key ingredients in a specification include: the primitive gates supported by the circuit class, the gates that can be decomposed to sequences of primitive gates, and the possible topology/connectivity restrictions.

This information is used e.g., in Program.compile() for validation and compilation.

Attributes

circuit	A rigid circuit template that defines this circuit specification.
decompositions	Quantum operations that are not quantum primitives for the circuit class, but are supported via specified decompositions.
graph	The allowed circuit topologies or connectivity of the class, modelled as a directed acyclic graph.
interactive	Whether the circuits in the class can be executed interactively, that is, the registers in the circuit are not reset between engine executions.
primitives	The primitive set of quantum operations directly supported by the circuit class.
short_name	short name of the circuit class

circuit

A rigid circuit template that defines this circuit specification.

If arbitrary topologies are allowed in the circuit class, this function will simply return None.

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

Returns

Blackbird circuit or template representing the circuit

Return type

Union[str, None]

decompositions

Quantum operations that are not quantum primitives for the circuit class, but are supported via specified decompositions.

This should be of the form

{'operation_name': {'option1': val, 'option2': val,...}}

For each operation specified in the dictionary, the Operation.decompose() method will be called during Program compilation, with keyword arguments given by the dictionary value.

Returns

the quantum operations that are supported by the circuit class via decomposition

Return type

dict[str, dict]

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

Whether the circuits in the class can be executed interactively, that is, the registers in the circuit are not reset between engine executions.

Returns

True if the circuit supports interactive use

Return type

bool

primitives

The primitive set of quantum operations directly supported by the circuit class.

Returns

the names of the quantum primitives the circuit class supports

Return type

set[str]

short_name = ''

short name of the circuit class

Type

str

Methods

add_loss(program, device)	Adds realistic loss to circuit.
compile(seq, registers)	Class-specific circuit compilation method.
decompose(seq)	Recursively decompose all gates in a given sequence, as allowed by the circuit specification.
init_circuit(layout)	Sets the circuit in the compiler class.
reset_circuit()	Resets the circuit and graph class attributes.
update_params(program, device)	Updates and checks parameters in the program circuit.

add_loss(program, device)

Adds realistic loss to circuit.

Child classes which are hardware compilers should override this method with device specific loss added to the circuit.

compile(seq, registers)

Class-specific circuit compilation method.

If additional compilation logic is required, child classes can redefine this method.

Parameters

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

• registers (Sequence[RegRef]) – quantum registers

Returns

modified circuit

Return type

Sequence[Command]

Raises

CircuitError – the given circuit cannot be validated to belong to this circuit class

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 Compiler).

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 Compiler).

   • 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

list[strawberryfields.program_utils.Command]

classmethod init_circuit(layout)

Sets the circuit in the compiler class.

Parameters

layout (str) – the circuit layout for the target device

Return type

None

classmethod reset_circuit()

Resets the circuit and graph class attributes.

Return type

None

update_params(program, device)

Updates and checks parameters in the program circuit.

Child classes can override this method with compiler specific logic. If no parameters need to be updated, and are separately checked, this method should not be overridden and be left empty.

Parameters

• program (Program) – Program containing the circuit and gate parameters

• device (DeviceSpec) – device specification containing the valid parameter values

Return type

None

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