Preset Passmanagers

qiskit.transpiler.preset_passmanagers.generate_preset_pass_manager(optimization_level=2, backend=None, target=None, basis_gates=None, inst_map=None, coupling_map=None, instruction_durations=None, backend_properties=None, timing_constraints=None, initial_layout=None, layout_method=None, routing_method=None, translation_method=None, scheduling_method=None, approximation_degree=1.0, seed_transpiler=None, unitary_synthesis_method='default', unitary_synthesis_plugin_config=None, hls_config=None, init_method=None, optimization_method=None, dt=None, qubits_initially_zero=True, *, _skip_target=False)

Generate a preset PassManager

This function is used to quickly generate a preset pass manager. Preset pass managers are the default pass managers used by the transpile() function. This function provides a convenient and simple method to construct a standalone PassManager object that mirrors what the transpile() function internally builds and uses.

The target constraints for the pass manager construction can be specified through a Target instance, a BackendV1 or BackendV2 instance, or via loose constraints (basis_gates, inst_map, coupling_map, backend_properties, instruction_durations, dt or timing_constraints). The order of priorities for target constraints works as follows: if a target input is provided, it will take priority over any backend input or loose constraints. If a backend is provided together with any loose constraint from the list above, the loose constraint will take priority over the corresponding backend constraint. This behavior is independent of whether the backend instance is of type BackendV1 or BackendV2, as summarized in the table below. The first column in the table summarizes the potential user-provided constraints, and each cell shows whether the priority is assigned to that specific constraint input or another input (target/backend(V1)/backend(V2)).

Parameters

• optimization_level (int) –

  The optimization level to generate a StagedPassManager for. By default optimization level 2 is used if this is not specified. This can be 0, 1, 2, or 3. Higher levels generate potentially more optimized circuits, at the expense of longer transpilation time:

  • 0: no optimization
  • 1: light optimization
  • 2: heavy optimization
  • 3: even heavier optimization

• backend (Backend) – An optional backend object which can be used as the source of the default values for the basis_gates, inst_map, coupling_map, backend_properties, instruction_durations, timing_constraints, and target. If any of those other arguments are specified in addition to backend they will take precedence over the value contained in the backend.

• target (Target) – The Target representing a backend compilation target. The following attributes will be inferred from this argument if they are not set: coupling_map, basis_gates, instruction_durations, inst_map, timing_constraints and backend_properties.

• basis_gates (list) – List of basis gate names to unroll to (e.g: ['u1', 'u2', 'u3', 'cx']).

• inst_map (InstructionScheduleMap) – DEPRECATED. Mapping object that maps gates to schedules. If any user defined calibration is found in the map and this is used in a circuit, transpiler attaches the custom gate definition to the circuit. This enables one to flexibly override the low-level instruction implementation.

• coupling_map (CouplingMap orlist) –

  Directed graph represented a coupling map. Multiple formats are supported:

  1. CouplingMap instance
  2. List, must be given as an adjacency matrix, where each entry specifies all directed two-qubit interactions supported by backend, e.g: [[0, 1], [0, 3], [1, 2], [1, 5], [2, 5], [4, 1], [5, 3]]

• instruction_durations (InstructionDurations orlist) –

  Dictionary of duration (in dt) for each instruction. If specified, these durations overwrite the gate lengths in backend.properties. Applicable only if scheduling_method is specified. The format of instruction_durations must be as follows: They must be given as an InstructionDurations instance or a list of tuples

  ` [(instruction_name, qubits, duration, unit), ...]. | [('cx', [0, 1], 12.3, 'ns'), ('u3', [0], 4.56, 'ns')] | [('cx', [0, 1], 1000), ('u3', [0], 300)] `

  If unit is omitted, the default is 'dt', which is a sample time depending on backend. If the time unit is 'dt', the duration must be an integer.

• dt (float) – Backend sample time (resolution) in seconds. If provided, this value will overwrite the dt value in instruction_durations. If None (default) and a backend is provided, backend.dt is used.

• timing_constraints (TimingConstraints) –

  Hardware time alignment restrictions. A quantum computer backend may report a set of restrictions, namely:

  • granularity: An integer value representing minimum pulse gate resolution in units of dt. A user-defined pulse gate should have duration of a multiple of this granularity value.
  • min_length: An integer value representing minimum pulse gate length in units of dt. A user-defined pulse gate should be longer than this length.
  • pulse_alignment: An integer value representing a time resolution of gate instruction starting time. Gate instruction should start at time which is a multiple of the alignment value.
  • acquire_alignment: An integer value representing a time resolution of measure instruction starting time. Measure instruction should start at time which is a multiple of the alignment value.

  This information will be provided by the backend configuration. If the backend doesn’t have any restriction on the instruction time allocation, then timing_constraints is None and no adjustment will be performed.

• initial_layout (Layout | List[int]) – Initial position of virtual qubits on physical qubits.

• layout_method (str) – The Pass to use for choosing initial qubit placement. Valid choices are 'trivial', 'dense', and 'sabre', representing TrivialLayout, DenseLayout and SabreLayout respectively. This can also be the external plugin name to use for the layout stage of the output StagedPassManager. You can see a list of installed plugins by using list_stage_plugins() with "layout" for the stage_name argument.

• routing_method (str) – The pass to use for routing qubits on the architecture. Valid choices are 'basic', 'lookahead', 'stochastic', 'sabre', and 'none' representing BasicSwap, LookaheadSwap, StochasticSwap, SabreSwap, and erroring if routing is required respectively. This can also be the external plugin name to use for the routing stage of the output StagedPassManager. You can see a list of installed plugins by using list_stage_plugins() with "routing" for the stage_name argument.

• translation_method (str) – The method to use for translating gates to basis gates. Valid choices 'translator', 'synthesis' representing BasisTranslator, and UnitarySynthesis respectively. This can also be the external plugin name to use for the translation stage of the output StagedPassManager. You can see a list of installed plugins by using list_stage_plugins() with "translation" for the stage_name argument.

• scheduling_method (str) – The pass to use for scheduling instructions. Valid choices are 'alap' and 'asap'. This can also be the external plugin name to use for the scheduling stage of the output StagedPassManager. You can see a list of installed plugins by using list_stage_plugins() with "scheduling" for the stage_name argument.

• backend_properties (BackendProperties) – Properties returned by a backend, including information on gate errors, readout errors, qubit coherence times, etc.

• approximation_degree (float) – Heuristic dial used for circuit approximation (1.0=no approximation, 0.0=maximal approximation).

• seed_transpiler (int) – Sets random seed for the stochastic parts of the transpiler.

• unitary_synthesis_method (str) – The name of the unitary synthesis method to use. By default 'default' is used. You can see a list of installed plugins with unitary_synthesis_plugin_names().

• unitary_synthesis_plugin_config (dict) – An optional configuration dictionary that will be passed directly to the unitary synthesis plugin. By default this setting will have no effect as the default unitary synthesis method does not take custom configuration. This should only be necessary when a unitary synthesis plugin is specified with the unitary_synthesis_method argument. As this is custom for each unitary synthesis plugin refer to the plugin documentation for how to use this option.

• hls_config (HLSConfig) – An optional configuration class HLSConfig that will be passed directly to HighLevelSynthesis transformation pass. This configuration class allows to specify for various high-level objects the lists of synthesis algorithms and their parameters.

• init_method (str) – The plugin name to use for the init stage of the output StagedPassManager. By default an external plugin is not used. You can see a list of installed plugins by using list_stage_plugins() with "init" for the stage name argument.

• optimization_method (str) – The plugin name to use for the optimization stage of the output StagedPassManager. By default an external plugin is not used. You can see a list of installed plugins by using list_stage_plugins() with "optimization" for the stage_name argument.

• qubits_initially_zero (bool) – Indicates whether the input circuit is zero-initialized.

Returns

The preset pass manager for the given options

Return type

StagedPassManager

Raises

ValueError – if an invalid value for optimization_level is passed in.

qiskit.transpiler.preset_passmanagers.level_0_pass_manager(pass_manager_config)

Level 0 pass manager: no explicit optimization other than mapping to backend.

This pass manager applies the user-given initial layout. If none is given, a trivial layout consisting of mapping the i-th virtual qubit to the i-th physical qubit is used. Any unused physical qubit is allocated as ancilla space.

The pass manager then unrolls the circuit to the desired basis, and transforms the circuit to match the coupling map.

Parameters

pass_manager_config (PassManagerConfig) – configuration of the pass manager.

Returns

a level 0 pass manager.

Raises

TranspilerError – if the passmanager config is invalid.

Return type

StagedPassManager

qiskit.transpiler.preset_passmanagers.level_1_pass_manager(pass_manager_config)

Level 1 pass manager: light optimization by simple adjacent gate collapsing.

This pass manager applies the user-given initial layout. If none is given, and a trivial layout (i-th virtual -> i-th physical) makes the circuit fit the coupling map, that is used. Otherwise, the circuit is mapped to the most densely connected coupling subgraph, and swaps are inserted to map. Any unused physical qubit is allocated as ancilla space. The pass manager then unrolls the circuit to the desired basis, and transforms the circuit to match the coupling map. Finally, optimizations in the form of adjacent gate collapse and redundant reset removal are performed.

Parameters

pass_manager_config (PassManagerConfig) – configuration of the pass manager.

Returns

a level 1 pass manager.

Raises

TranspilerError – if the passmanager config is invalid.

Return type

StagedPassManager

qiskit.transpiler.preset_passmanagers.level_2_pass_manager(pass_manager_config)

Level 2 pass manager: medium optimization by initial layout selection and gate cancellation using commutativity rules.

This pass manager applies the user-given initial layout. If none is given, a search for a perfect layout (i.e. one that satisfies all 2-qubit interactions) is conducted. If no such layout is found, qubits are laid out on the most densely connected subset which also exhibits the best gate fidelities.

The pass manager then transforms the circuit to match the coupling constraints. It is then unrolled to the basis, and any flipped cx directions are fixed. Finally, optimizations in the form of commutative gate cancellation and redundant reset removal are performed.

Parameters

pass_manager_config (PassManagerConfig) – configuration of the pass manager.

Returns

a level 2 pass manager.

Raises

TranspilerError – if the passmanager config is invalid.

Return type

StagedPassManager

qiskit.transpiler.preset_passmanagers.level_3_pass_manager(pass_manager_config)

Level 3 pass manager: heavy optimization by noise adaptive qubit mapping and gate cancellation using commutativity rules and unitary synthesis.

This pass manager applies the user-given initial layout. If none is given, a search for a perfect layout (i.e. one that satisfies all 2-qubit interactions) is conducted. If no such layout is found, and device calibration information is available, the circuit is mapped to the qubits with best readouts and to CX gates with highest fidelity.

The pass manager then transforms the circuit to match the coupling constraints. It is then unrolled to the basis, and any flipped cx directions are fixed. Finally, optimizations in the form of commutative gate cancellation, resynthesis of two-qubit unitary blocks, and redundant reset removal are performed.

Parameters

pass_manager_config (PassManagerConfig) – configuration of the pass manager.

Returns

a level 3 pass manager.

Raises

TranspilerError – if the passmanager config is invalid.

Return type

StagedPassManager

qiskit.transpiler.preset_passmanagers.common.generate_control_flow_options_check(layout_method=None, routing_method=None, translation_method=None, optimization_method=None, scheduling_method=None, basis_gates=(), target=None)

Generate a pass manager that, when run on a DAG that contains control flow, fails with an error message explaining the invalid options, and what could be used instead.

Returns

a pass manager that populates the contains_x properties for each of the control-flow operations, and raises an error if any of the given options do not support control flow, but a circuit with control flow is given.

Return type

PassManager

qiskit.transpiler.preset_passmanagers.common.generate_error_on_control_flow(message)

Get a pass manager that always raises an error if control flow is present in a given circuit.

qiskit.transpiler.preset_passmanagers.common.generate_unroll_3q(target, basis_gates=None, approximation_degree=None, unitary_synthesis_method='default', unitary_synthesis_plugin_config=None, hls_config=None, qubits_initially_zero=True)

Generate an unroll >3q PassManager

Parameters

• target (Target) – the Target object representing the backend
• basis_gates (list) – A list of str gate names that represent the basis gates on the backend target
• approximation_degree (Optional[float]) – The heuristic approximation degree to use. Can be between 0 and 1.
• unitary_synthesis_method (str) – The unitary synthesis method to use. You can see a list of installed plugins with unitary_synthesis_plugin_names().
• unitary_synthesis_plugin_config (dict) – The optional dictionary plugin configuration, this is plugin specific refer to the specified plugin’s documentation for how to use.
• hls_config (HLSConfig) – An optional configuration class to use for HighLevelSynthesis pass. Specifies how to synthesize various high-level objects.
• qubits_initially_zero (bool) – Indicates whether the input circuit is zero-initialized.

Returns

The unroll 3q or more pass manager

Return type

PassManager

qiskit.transpiler.preset_passmanagers.common.generate_embed_passmanager(coupling_map)

Generate a layout embedding PassManager

This is used to generate a PassManager object that can be used to expand and apply an initial layout to a circuit

Parameters

coupling_map (Union[CouplingMap, Target) – The coupling map for the backend to embed the circuit to.

Returns

The embedding passmanager that assumes the layout property

set has been set in earlier stages

Return type

PassManager

qiskit.transpiler.preset_passmanagers.common.generate_routing_passmanager(routing_pass, target, coupling_map=None, vf2_call_limit=None, backend_properties=None, seed_transpiler=None, check_trivial=False, use_barrier_before_measurement=True, vf2_max_trials=None)

Generate a routing PassManager

Parameters

• routing_pass (TransformationPass) – The pass which will perform the routing
• target (Target) – the Target object representing the backend
• coupling_map (CouplingMap) – The coupling map of the backend to route for
• vf2_call_limit (int) – The internal call limit for the vf2 post layout pass. If this is None or 0 the vf2 post layout will not be run.
• backend_properties (BackendProperties) – Properties of a backend to synthesize for (e.g. gate fidelities).
• seed_transpiler (int) – Sets random seed for the stochastic parts of the transpiler.
• check_trivial (bool) – If set to true this will condition running the VF2PostLayout pass after routing on whether a trivial layout was tried and was found to not be perfect. This is only needed if the constructed pass manager runs TrivialLayout as a first layout attempt and uses it if it’s a perfect layout (as is the case with preset pass manager level 1).
• use_barrier_before_measurement (bool) – If true (the default) the BarrierBeforeFinalMeasurements transpiler pass will be run prior to the specified pass in the routing_pass argument.
• vf2_max_trials (int) – The maximum number of trials to run VF2 when evaluating the vf2 post layout pass. If this is None or 0 the vf2 post layout will not be run.

Returns

The routing pass manager

Return type

PassManager

qiskit.transpiler.preset_passmanagers.common.generate_pre_op_passmanager(target=None, coupling_map=None, remove_reset_in_zero=False)

Generate a pre-optimization loop PassManager

This pass manager will check to ensure that directionality from the coupling map is respected

Parameters

• target (Target) – the Target object representing the backend
• coupling_map (CouplingMap) – The coupling map to use
• remove_reset_in_zero (bool) – If True include the remove reset in zero pass in the generated PassManager

Returns

The pass manager

Return type

PassManager

qiskit.transpiler.preset_passmanagers.common.generate_translation_passmanager(target, basis_gates=None, method='translator', approximation_degree=None, coupling_map=None, backend_props=None, unitary_synthesis_method='default', unitary_synthesis_plugin_config=None, hls_config=None, qubits_initially_zero=True)

Generate a basis translation PassManager

Parameters

• target (Target) – the Target object representing the backend
• basis_gates (list) – A list of str gate names that represent the basis gates on the backend target
• method (str) – The basis translation method to use
• approximation_degree (Optional[float]) – The heuristic approximation degree to use. Can be between 0 and 1.
• coupling_map (CouplingMap) – the coupling map of the backend in case synthesis is done on a physical circuit. The directionality of the coupling_map will be taken into account if pulse_optimize is True/None and natural_direction is True/None.
• unitary_synthesis_plugin_config (dict) – The optional dictionary plugin configuration, this is plugin specific refer to the specified plugin’s documentation for how to use.
• backend_props (BackendProperties) – Properties of a backend to synthesize for (e.g. gate fidelities).
• unitary_synthesis_method (str) – The unitary synthesis method to use. You can see a list of installed plugins with unitary_synthesis_plugin_names().
• hls_config (HLSConfig) – An optional configuration class to use for HighLevelSynthesis pass. Specifies how to synthesize various high-level objects.
• qubits_initially_zero (bool) – Indicates whether the input circuit is zero-initialized.

Returns

The basis translation pass manager

Return type

PassManager

Raises

TranspilerError – If the method kwarg is not a valid value

qiskit.transpiler.preset_passmanagers.common.generate_scheduling(instruction_durations, scheduling_method, timing_constraints, inst_map, target=None)

Generate a post optimization scheduling PassManager

Parameters

• instruction_durations (dict) – The dictionary of instruction durations
• scheduling_method (str) – The scheduling method to use, can either be 'asap'/'as_soon_as_possible' or 'alap'/'as_late_as_possible'
• timing_constraints (TimingConstraints) – Hardware time alignment restrictions.
• inst_map (InstructionScheduleMap) – DEPRECATED. Mapping object that maps gate to schedule.
• target (Target) – The Target object representing the backend

Returns

The scheduling pass manager

Return type

PassManager

Raises

TranspilerError – If the scheduling_method kwarg is not a valid value