import MainEngine from 'projectq/src/cengines/main.js'

public class | source

MainEngine

Extends:

BasicEngine → MainEngine

The MainEngine class provides all functionality of the main compiler engine.

It initializes all further compiler engines (calls, e.g., .next_engine=...) and keeps track of measurement results and active qubits (and their IDs).

Attributes: next_engine (BasicEngine): Next compiler engine (or the back-end). main_engine (MainEngine): Self. active_qubits (WeakSet): WeakSet containing all active qubits dirty_qubits (Set): Containing all dirty qubit ids backend (BasicEngine): Access the back-end. mapper (BasicMapperEngine): Access to the mapper if there is one.

Constructor Summary

Public Constructor
public	constructor(backend: BasicEngine, engineList: Array<BasicEngine>, verbose: boolean)

Member Summary

Public Members
public	activeQubits: *
public	backend: *
public	dirtyQubits: *
public	main: *
public	mapper: *
public	next: *
public	verbose: *

Private Members
private	_measurements: {}
private	_qubitIdx: number

Method Summary

Public Methods
public	deallocate() Destroy the main engine.
public	flush(deallocateQubits: boolean) Flush the entire circuit down the pipeline, clearing potential buffers (of, e.g., optimizers).
public	getMeasurementResult(qubit: BasicQubit): * Return the classical value of a measured qubit, given that an engine registered this result previously (see setMeasurementResult).
public	getNewQubitID(): number Returns a unique qubit id to be used for the next qubit allocation.
public	receive(commandList: Command[]) Forward the list of commands to the first engine.
public	send(commandList: *) Forward the list of commands to the next engine in the pipeline.
public	setMeasurementResult(qubit: BasicQubit, value: boolean) Register a measurement result

Inherited Summary

From class BasicEngine
public	isLastEngine: boolean
public	allocateQubit(dirty: boolean): Qureg Return a new qubit as a list containing 1 qubit object (quantum register of size 1).
public	allocateQureg(n: number): Qureg Allocate n qubits and return them as a quantum register, which is a list of qubit objects.
public	deallocateQubit(qubit: BasicQubit) Deallocate a qubit (and sends the deallocation command down the pipeline).
public	isAvailable(cmd: Command): boolean Default implementation of isAvailable: Ask the next engine whether a command is available, i.e., whether it can be executed by the next engine(s).
public	isMetaTagSupported(metaTag: function): boolean Check if there is a compiler engine handling the meta tag
public	receive()
public	send(commandList: Command[]) Forward the list of commands to the next engine in the pipeline.

Public Constructors

public constructor(backend: BasicEngine, engineList: Array<BasicEngine>, verbose: boolean) source

Override:

BasicEngine#constructor

Params:

Name	Type	Attribute	Description
backend	BasicEngine		Backend to send the compiled circuit to.
engineList	Array<BasicEngine>		List of engines / backends to use as compiler engines. Note: The engine list must not contain multiple mappers (instances of BasicMapperEngine). Default: getEngineList()
verbose	boolean		Either print full or compact error messages. Default: false (i.e. compact error messages).

Example:

const eng = new MainEngine() // uses default engine_list and the Simulator

Instead of the default `engine_list` one can use, e.g., one of the IBM
setups which defines a custom `engine_list` useful for one of the IBM
chips

const eng = new MainEngine(new Simulator, getEngineList())
// eng uses the default Simulator backend

Alternatively, one can specify all compiler engines explicitly, e.g.,

const rule_set = new DecompositionRuleSet()
const engines = [new AutoReplacer(rule_set), new TagRemover(), new LocalOptimizer(3)]
const eng = new MainEngine(new Simulator(), engines)

Public Members

public activeQubits: * source

public backend: * source

public dirtyQubits: * source

public main: * source

public mapper: * source

public next: * source

public verbose: * source

Private Members

private _measurements: {} source

private _qubitIdx: number source

Public Methods

public deallocate() source

Destroy the main engine. Flushes the entire circuit down the pipeline, clearing all temporary buffers (in, e.g., optimizers).

public flush(deallocateQubits: boolean) source

Flush the entire circuit down the pipeline, clearing potential buffers (of, e.g., optimizers).

Params:

Name	Type	Attribute	Description
deallocateQubits	boolean		If true, deallocates all qubits that are still alive (invalidating references to them by setting their id to -1).

public getMeasurementResult(qubit: BasicQubit): * source

Return the classical value of a measured qubit, given that an engine registered this result previously (see setMeasurementResult).

Params:

Name	Type	Attribute	Description
qubit	BasicQubit		Qubit of which to get the measurement result.

Return:

Example:


const eng = new MainEngine()
const qubit = eng.allocateQubit() // quantum register of size 1
H.or(qubit)
Measure.or(qubit)
eng.getMeasurementResult(qubit[0]) == qubit.toNumber()

public getNewQubitID(): number source

Returns a unique qubit id to be used for the next qubit allocation.

Return:

number

New unique qubit id.

public receive(commandList: Command[]) source

Forward the list of commands to the first engine.

Override:

BasicEngine#receive

Params:

Name	Type	Attribute	Description
commandList	Command[]		List of commands to receive (and then send on)

public send(commandList: *) source

Forward the list of commands to the next engine in the pipeline. It also shortens exception stack traces if this.verbose is false.

Override:

BasicEngine#send

Params:

Name	Type	Attribute	Description
commandList	*

public setMeasurementResult(qubit: BasicQubit, value: boolean) source

The engine being responsible for measurement results needs to register these results with the master engine such that they are available when the user calls an int() or bool() conversion operator on a measured qubit.

Params:

Name	Type	Attribute	Description
qubit	BasicQubit		Qubit for which to register the measurement result.
value	boolean		Boolean value of the measurement outcome (true / false = 1 / 0 respectively).