Interface class for a quantum computing simulator state. More...

#include <State.h>

Inheritance diagram for Simulators::IState:

Collaboration diagram for Simulators::IState:

Public Member Functions
virtual	~IState ()=default
	Virtual destructor.

virtual size_t	AllocateQubits (size_t num_qubits)=0
	Allocates qubits.

virtual std::vector< double >	AllProbabilities ()=0
	Returns the probabilities of all possible outcomes.

virtual std::complex< double >	Amplitude (Types::qubit_t outcome)=0
	Returns the amplitude of the specified state.

virtual std::complex< double >	AmplitudeRaw (Types::qubit_t outcome)=0
	Gets the amplitude.

virtual void	ApplyReset (const Types::qubits_vector &qubits)=0
	Performs a reset of the specified qubits.

virtual void	Clear ()=0
	Clears the state.

void	ClearObservers ()
	Clears all observers.

virtual void	Configure (const char key, const char value)=0
	Configures the state.

virtual double	ExpectationValue (const std::string &pauliString)=0
	Returns the expected value of a Pauli string.

virtual void	Flush ()=0
	Flushes the applied operations.

virtual std::string	GetConfiguration (const char *key) const =0
	Returns configuration value.

virtual long long int	GetGatesCounter () const
	Returns the gates counter.

virtual bool	GetMultithreading () const =0
	Get the multithreading flag.

virtual size_t	GetNumberOfQubits () const =0
	Returns the number of qubits.

virtual SimulationType	GetSimulationType () const =0
	Returns the type of simulation.

virtual SimulatorType	GetType () const =0
	Returns the type of simulator.

virtual void	IncrementGatesCounter ()
	Increments the gates counter.

virtual void	Initialize ()=0
	Initializes the state.

virtual void	InitializeState (size_t num_qubits, AER::Vector< std::complex< double > > &amplitudes)=0
	Initializes the state.

virtual void	InitializeState (size_t num_qubits, Eigen::VectorXcd &amplitudes)=0
	Initializes the state.

virtual void	InitializeState (size_t num_qubits, std::vector< std::complex< double > > &amplitudes)=0
	Initializes the state.

virtual bool	IsQcsim () const =0
	Returns if the simulator is a qcsim simulator.

virtual size_t	Measure (const Types::qubits_vector &qubits)=0
	Performs a measurement on the specified qubits.

virtual std::vector< bool >	MeasureMany (const Types::qubits_vector &qubits)=0
	Performs a measurement on the specified qubits.

virtual Types::qubit_t	MeasureNoCollapse ()=0
	Measures all the qubits without collapsing the state.

virtual std::vector< bool >	MeasureNoCollapseMany ()=0
	Measures all the qubits without collapsing the state.

virtual std::vector< double >	Probabilities (const Types::qubits_vector &qubits)=0
	Returns the probabilities of the specified outcomes.

virtual double	Probability (Types::qubit_t outcome)=0
	Returns the probability of the specified outcome.

virtual std::complex< double >	ProjectOnZero ()=0
	Projects the state onto the zero state.

void	RegisterObserver (const std::shared_ptr< ISimulatorObserver > &observer)
	Registers an observer.

virtual void	Reset ()=0
	Just resets the state to 0.

virtual void	RestoreInternalDestructiveSavedState ()=0
	Restores the state from the internally saved state.

virtual void	RestoreState ()=0
	Restores the state from the internally saved state.

virtual std::unordered_map< Types::qubit_t, Types::qubit_t >	SampleCounts (const Types::qubits_vector &qubits, size_t shots=1000)=0
	Returns the counts of the outcomes of measurement of the specified qubits, for repeated measurements.

virtual std::unordered_map< std::vector< bool >, Types::qubit_t >	SampleCountsMany (const Types::qubits_vector &qubits, size_t shots=1000)=0
	Returns the counts of the outcomes of measurement of the specified qubits, for repeated measurements.

virtual void	SaveState ()=0
	Saves the state to internal storage.

virtual void	SaveStateToInternalDestructive ()=0
	Saves the state to internal storage.

virtual void	SetGatesCounter (long long int)
	Sets the gates counter.

virtual void	SetInitialQubitsMap (const std::vector< long long int > &initialMap)
	Sets the initial qubits map, if possible.

virtual void	SetLookaheadDepth (int)
	Sets the lookahead depth for swap optimization.

virtual void	SetLookaheadDepthWithHeuristic (int)
	Sets the lookahead depth for swap optimization.

virtual void	SetMultithreading (bool multithreading=true)=0
	Enable/disable multithreading.

virtual void	SetUpcomingGates (const std::vector< std::shared_ptr< Circuits::IOperation< double > > > &)
	Supplies upcoming gates for lookahead swap optimization.

virtual void	SetUseOptimalMeetingPosition (bool)
	Enables or disables optimal meeting position for MPS swaps.

virtual bool	SupportsMPSSwapOptimization () const
	Returns if the simulator supports MPS swap optimization.

void	UnregisterObserver (const std::shared_ptr< ISimulatorObserver > &observer)
	Unregisters an observer.

Protected Member Functions
void	DontNotify ()
	Stops notifying observers.

void	Notify ()
	Starts notifying observers.

void	NotifyObservers (const Types::qubits_vector &affectedQubits)
	Notifies observers.

Detailed Description

Interface class for a quantum computing simulator state.

Use this interface if only the state of the simulator is required.

See also: ISimulator

Definition at line 103 of file State.h.

Constructor & Destructor Documentation

◆ ~IState()

virtual Simulators::IState::~IState ( )

virtualdefault

Virtual destructor.

Since this is a base class, the destructor should be virtual.

Member Function Documentation

◆ AllocateQubits()

virtual size_t Simulators::IState::AllocateQubits ( size_t num_qubits )

pure virtual

Allocates qubits.

This function is called to allocate qubits.

Parameters

num_qubits The number of qubits to allocate.

Returns: The index of the first qubit allocated.

Referenced by AllocateQubits().

◆ AllProbabilities()

virtual std::vector< double > Simulators::IState::AllProbabilities ( )

pure virtual

Returns the probabilities of all possible outcomes.

Use it to obtain the probabilities of all possible outcomes.

See also: IState::Probability; IState::Amplitude; IState::Probabilities

Returns: A vector with the probabilities of all possible outcomes.

Referenced by AllProbabilities().

◆ Amplitude()

virtual std::complex< double > Simulators::IState::Amplitude ( Types::qubit_t outcome )

pure virtual

Returns the amplitude of the specified state.

Use it to obtain the amplitude of the specified state.

See also: IState::Probability; IState::Probabilities

Parameters

outcome The outcome to obtain the amplitude for.

Returns: The amplitude of the specified outcome.

Referenced by Amplitude().

◆ AmplitudeRaw()

virtual std::complex< double > Simulators::IState::AmplitudeRaw ( Types::qubit_t outcome )

pure virtual

Gets the amplitude.

Gets the amplitude, from the internal storage if needed. This is needed only for the composite simulator, for an optimization for qiskit aer.

◆ ApplyReset()

virtual void Simulators::IState::ApplyReset ( const Types::qubits_vector & qubits )

pure virtual

Performs a reset of the specified qubits.

Measures the qubits and for those that are 1, applies X on them

Parameters

qubits A vector with the qubits to be reset.

◆ Clear()

virtual void Simulators::IState::Clear ( )

pure virtual

Clears the state.

Sets the number of allocated qubits to 0 and clears the state. After this qubits allocation is required then calling IState::AllocateQubits in order to use the simulator.

Referenced by ClearSimulator().

◆ ClearObservers()

void Simulators::IState::ClearObservers ( )

inline

Clears all observers.

Definition at line 480 of file State.h.

◆ Configure()

virtual void Simulators::IState::Configure	(	const char *	key,
		const char *	value
	)

pure virtual

Configures the state.

This function is called to configure the simulator. Currently only aer supports configuration, qcsim will gracefully ignore this.

Parameters

key	The key of the configuration option.
value	The value of the configuration.

Referenced by ConfigureSimulator().

◆ DontNotify()

void Simulators::IState::DontNotify ( )

inlineprotected

Stops notifying observers.

Use it to stop notifying observers until Notify is called.

Definition at line 631 of file State.h.

◆ ExpectationValue()

virtual double Simulators::IState::ExpectationValue ( const std::string & pauliString )

pure virtual

Returns the expected value of a Pauli string.

Use it to obtain the expected value of a Pauli string. The Pauli string is a string of characters representing the Pauli operators, e.g. "XIZY". The length of the string should be less or equal to the number of qubits (if it's less, it's completed with I).

Parameters

pauliString The Pauli string to obtain the expected value for.

Returns: The expected value of the specified Pauli string.

◆ Flush()

virtual void Simulators::IState::Flush ( )

pure virtual

Flushes the applied operations.

This function is called to flush the applied operations. qcsim applies them right away, so this has no effect on it, but qiskit aer does not.

Referenced by FlushSimulator().

◆ GetConfiguration()

virtual std::string Simulators::IState::GetConfiguration ( const char * key ) const

pure virtual

Returns configuration value.

This function is called get a configuration value.

Parameters

key	The key of the configuration value.

Returns: The configuration value as a string.

Referenced by GetConfiguration().

◆ GetGatesCounter()

virtual long long int Simulators::IState::GetGatesCounter ( ) const

inlinevirtual

Returns the gates counter.

Usually does nothing, except for MPS simulators that support swap optimization.

Returns: The number of gates executed in the circuit.

Definition at line 244 of file State.h.

◆ GetMultithreading()

virtual bool Simulators::IState::GetMultithreading ( ) const

pure virtual

Get the multithreading flag.

Returns the multithreading flag.

Returns: The multithreading flag.

Referenced by GetMultithreading().

◆ GetNumberOfQubits()

virtual size_t Simulators::IState::GetNumberOfQubits ( ) const

pure virtual

Returns the number of qubits.

This function is called to obtain the number of the allocated qubits.

Returns: The number of qubits.

Referenced by GetNumberOfQubits().

◆ GetSimulationType()

virtual SimulationType Simulators::IState::GetSimulationType ( ) const

pure virtual

Returns the type of simulation.

Returns: The type of simulation.

See also: SimulationType

◆ GetType()

virtual SimulatorType Simulators::IState::GetType ( ) const

pure virtual

Returns the type of simulator.

Returns: The type of simulator.

See also: SimulatorType

◆ IncrementGatesCounter()

virtual void Simulators::IState::IncrementGatesCounter ( )

inlinevirtual

Increments the gates counter.

Usually does nothing, except for MPS simulators that support swap optimization. Increments the position in the circuit from where the execution should continue. Useful for classically controlled gates, for the case when the controlled gate is not executed.

Definition at line 261 of file State.h.

◆ Initialize()

virtual void Simulators::IState::Initialize ( )

pure virtual

Initializes the state.

This function is called when the simulator is initialized. Call it after the qubits allocation.

See also: IState::AllocateQubits

Referenced by InitializeSimulator().

◆ InitializeState() [1/3]

virtual void Simulators::IState::InitializeState	(	size_t	num_qubits,
		AER::Vector< std::complex< double > > &	amplitudes
	)

pure virtual

Initializes the state.

This function is called when the simulator is initialized. Call it only on a non-initialized state. This is good only for a statevector simulator and should be used only by calling from a composite simulator.

Parameters

num_qubits	The number of qubits to initialize the state with.
amplitudes	A vector with the amplitudes to initialize the state with.

◆ InitializeState() [2/3]

virtual void Simulators::IState::InitializeState	(	size_t	num_qubits,
		Eigen::VectorXcd &	amplitudes
	)

pure virtual

Initializes the state.

This function is called when the simulator is initialized. Call it only on a non-initialized state. This is good only for a statevector simulator and should be used only by calling from a composite simulator.

Parameters

num_qubits	The number of qubits to initialize the state with.
amplitudes	A vector with the amplitudes to initialize the state with.

◆ InitializeState() [3/3]

virtual void Simulators::IState::InitializeState	(	size_t	num_qubits,
		std::vector< std::complex< double > > &	amplitudes
	)

pure virtual

Initializes the state.

This function is called when the simulator is initialized. Call it only on a non-initialized state. This is good only for a statevector simulator and should be used only by calling from a composite simulator.

Parameters

num_qubits	The number of qubits to initialize the state with.
amplitudes	A vector with the amplitudes to initialize the state with.

◆ IsQcsim()

virtual bool Simulators::IState::IsQcsim ( ) const

pure virtual

Returns if the simulator is a qcsim simulator.

Returns if the simulator is a qcsim simulator. This is just a helper function to ease things up: qcsim has different functionality exposed sometimes so it's good to know if we deal with qcsim or with qiskit aer.

Returns: True if the simulator is a qcsim simulator, false otherwise.

Referenced by IsQcsim().

◆ Measure()

virtual size_t Simulators::IState::Measure ( const Types::qubits_vector & qubits )

pure virtual

Performs a measurement on the specified qubits.

Don't use it if the number of qubits is larger than the number of bits in the size_t type (usually 64), as the outcome will be undefined

Parameters

qubits A vector with the qubits to be measured.

Returns: The outcome of the measurements, the first qubit result is the least significant bit.

◆ MeasureMany()

virtual std::vector< bool > Simulators::IState::MeasureMany ( const Types::qubits_vector & qubits )

pure virtual

Performs a measurement on the specified qubits.

Parameters

qubits A vector with the qubits to be measured.

Returns: The outcome of the measurements

◆ MeasureNoCollapse()

virtual Types::qubit_t Simulators::IState::MeasureNoCollapse ( )

pure virtual

Measures all the qubits without collapsing the state.

Measures all the qubits without collapsing the state, allowing to perform multiple shots. This is to be used only internally, only for the statevector simulators (or those based on them, as the composite ones). For the qiskit aer case, SaveStateToInternalDestructive is needed to be called before this. If one wants to use the simulator after such measurement(s), RestoreInternalDestructiveSavedState should be called at the end.

Don't use this for more qubits than the size of Types::qubit_t, as the result is packed in a limited number of bits (e.g. 64 bits for uint64_t)

Returns: The result of the measurements, the first qubit result is the least significant bit.

◆ MeasureNoCollapseMany()

virtual std::vector< bool > Simulators::IState::MeasureNoCollapseMany ( )

pure virtual

Measures all the qubits without collapsing the state.

Measures all the qubits without collapsing the state, allowing to perform multiple shots. This is to be used only internally, only for the statevector simulators (or those based on them, as the composite ones). For the qiskit aer case, SaveStateToInternalDestructive is needed to be called before this. If one wants to use the simulator after such measurement(s), RestoreInternalDestructiveSavedState should be called at the end.

Use this for more qubits than the size of Types::qubit_t

Returns: The result of the measurements

◆ Notify()

void Simulators::IState::Notify ( )

inlineprotected

Starts notifying observers.

Use it to allow notifying observers.

Definition at line 638 of file State.h.

◆ NotifyObservers()

void Simulators::IState::NotifyObservers ( const Types::qubits_vector & affectedQubits )

inlineprotected

Notifies observers.

Called when the state changes, to notify observers about it.

Parameters

affectedQubits A vector with the qubits that were affected by the change.

Definition at line 647 of file State.h.

◆ Probabilities()

virtual std::vector< double > Simulators::IState::Probabilities ( const Types::qubits_vector & qubits )

pure virtual

Returns the probabilities of the specified outcomes.

Use it to obtain the probabilities of the specified outcomes.

See also: IState::Probability; IState::Amplitude

Parameters

qubits A vector with the qubits configuration outcomes.

Returns: A vector with the probabilities for the specified qubit configurations.

◆ Probability()

virtual double Simulators::IState::Probability ( Types::qubit_t outcome )

pure virtual

Returns the probability of the specified outcome.

Use it to obtain the probability to obtain the specified outcome, if all qubits are measured.

See also: IState::Amplitude; IState::Probabilities

Parameters

outcome The outcome to obtain the probability for.

Returns: The probability of the specified outcome.

Referenced by Probability().

◆ ProjectOnZero()

virtual std::complex< double > Simulators::IState::ProjectOnZero ( )

pure virtual

Projects the state onto the zero state.

Use it to project the state onto the zero state. For most simulator is the same as calling Amplitude(0), but for some simulators it can be optimized to be faster than calling Amplitude(0). This for now is done for qcsim mps and gpu mps.

See also: IState::Amplitude; IState::Probability

Returns: The inner product result as a complex number.

◆ RegisterObserver()

void Simulators::IState::RegisterObserver ( const std::shared_ptr< ISimulatorObserver > & observer )

inline

Registers an observer.

Registers an observer that will be notified when the state changes.

See also: ISimulatorObserver

Parameters

observer A smart pointer to an observer.

Definition at line 459 of file State.h.

◆ Reset()

virtual void Simulators::IState::Reset ( )

pure virtual

Just resets the state to 0.

Does not destroy the internal state, just resets it to zero (as a 'reset' op on each qubit would do).

Referenced by ResetSimulator().

◆ RestoreInternalDestructiveSavedState()

virtual void Simulators::IState::RestoreInternalDestructiveSavedState ( )

pure virtual

Restores the state from the internally saved state.

Restores the state from the internally saved state, if needed. This does something only for qiskit aer.

Referenced by RestoreInternalDestructiveSavedState().

◆ RestoreState()

virtual void Simulators::IState::RestoreState ( )

pure virtual

Restores the state from the internally saved state.

Restores the state from the internally saved state, if needed. To be used in order to recover the state after doing measurements, for multiple shots executions. In the first phase, only qcsim will implement this.

Referenced by RestoreState().

◆ SampleCounts()

virtual std::unordered_map< Types::qubit_t, Types::qubit_t > Simulators::IState::SampleCounts	(	const Types::qubits_vector &	qubits,
		size_t	shots = `1000`
	)

pure virtual

Returns the counts of the outcomes of measurement of the specified qubits, for repeated measurements.

Use it to obtain the counts of the outcomes of the specified qubits measurements. The state is not collapsed, so the measurement can be repeated 'shots' times.

Don't use it if the number of qubits is larger than the number of bits in the Types::qubit_t type (usually 64), as the outcome will be undefined.

Parameters

qubits	A vector with the qubits to be measured.
shots	The number of shots to perform.

Returns: A map with the counts for the otcomes of measurements of the specified qubits.

◆ SampleCountsMany()

virtual std::unordered_map< std::vector< bool >, Types::qubit_t > Simulators::IState::SampleCountsMany	(	const Types::qubits_vector &	qubits,
		size_t	shots = `1000`
	)

pure virtual

Returns the counts of the outcomes of measurement of the specified qubits, for repeated measurements.

Use it to obtain the counts of the outcomes of the specified qubits measurements. The state is not collapsed, so the measurement can be repeated 'shots' times.

Parameters

qubits	A vector with the qubits to be measured.
shots	The number of shots to perform.

Returns: A map with the counts for the otcomes of measurements of the specified qubits.

◆ SaveState()

virtual void Simulators::IState::SaveState ( )

pure virtual

Saves the state to internal storage.

Saves the state to internal storage, if needed. Calling this will not destroy the internal state, unlike the 'Destructive' variant. To be used in order to recover the state after doing measurements, for multiple shots executions. In the first phase, only qcsim will implement this.

Referenced by SaveState().

◆ SaveStateToInternalDestructive()

virtual void Simulators::IState::SaveStateToInternalDestructive ( )

pure virtual

Saves the state to internal storage.

Saves the state to internal storage, if needed. Calling this should consider as the simulator is gone to uninitialized. Either do not use it except for getting amplitudes, or reinitialize the simulator after calling it. This is needed only for the composite simulator, for an optimization for qiskit aer.

Referenced by SaveStateToInternalDestructive().

◆ SetGatesCounter()

virtual void Simulators::IState::SetGatesCounter ( long long int )

inlinevirtual

Sets the gates counter.

Usually does nothing, except for MPS simulators that support swap optimization.

Parameters

counter The position in the circuit from where the execution should continue.

Definition at line 253 of file State.h.

◆ SetInitialQubitsMap()

virtual void Simulators::IState::SetInitialQubitsMap ( const std::vector< long long int > & initialMap )

inlinevirtual

Sets the initial qubits map, if possible.

This will do nothing for most simulators, but for the MPS simulator it will set the initial qubits if it supports it - that is, for qcsim and the gpu simulator it can set the mapping of the qubits to the positions in the chain, which can be used to optimize the swapping cost.

Definition at line 193 of file State.h.

◆ SetLookaheadDepth()

virtual void Simulators::IState::SetLookaheadDepth ( int )

inlinevirtual

Sets the lookahead depth for swap optimization.

Controls how many upcoming 2-qubit gates are considered when choosing the swap meeting position. 0 means no lookahead (immediate cost only). Only effective for MPS simulators. Requires upcoming gates to be supplied via SetUpcomingGates.

Definition at line 214 of file State.h.

◆ SetLookaheadDepthWithHeuristic()

virtual void Simulators::IState::SetLookaheadDepthWithHeuristic ( int )

inlinevirtual

Sets the lookahead depth for swap optimization.

Controls how many upcoming 2-qubit gates are considered when choosing the swap meeting position. 0 means no lookahead (immediate cost only). Only effective for MPS simulators. Requires upcoming gates to be supplied via SetUpcomingGates. This value sets a number of gates to lookahead without much cost increase.

Definition at line 225 of file State.h.

◆ SetMultithreading()

virtual void Simulators::IState::SetMultithreading ( bool multithreading = true )

pure virtual

Enable/disable multithreading.

Enable/disable multithreading. Default is enabled.

Parameters

multithreading A flag to indicate if multithreading should be enabled.

Referenced by SetMultithreading().

◆ SetUpcomingGates()

virtual void Simulators::IState::SetUpcomingGates ( const std::vector< std::shared_ptr< Circuits::IOperation< double > > > & )

inlinevirtual

Supplies upcoming gates for lookahead swap optimization.

The simulator uses these to evaluate swap costs for future gates when choosing where to meet. Only effective for MPS simulators with lookahead depth > 0.

Definition at line 234 of file State.h.

◆ SetUseOptimalMeetingPosition()

virtual void Simulators::IState::SetUseOptimalMeetingPosition ( bool )

inlinevirtual

Enables or disables optimal meeting position for MPS swaps.

When enabled, the MPS simulator uses actual bond dimensions to find the cheapest meeting position for non-adjacent qubit swaps instead of the default heuristic. Does nothing for non-MPS simulators.

Definition at line 204 of file State.h.

◆ SupportsMPSSwapOptimization()

virtual bool Simulators::IState::SupportsMPSSwapOptimization ( ) const

inlinevirtual

Returns if the simulator supports MPS swap optimization.

Used to check if the simulator supports MPS swap optimization.

Returns: True if the simulator supports MPS swap optimization, false otherwise.

Definition at line 183 of file State.h.

◆ UnregisterObserver()

void Simulators::IState::UnregisterObserver ( const std::shared_ptr< ISimulatorObserver > & observer )

inline

Unregisters an observer.

Unegisters an observer.

See also: ISimulatorObserver

Parameters

observer A smart pointer to an observer.

Definition at line 471 of file State.h.

The documentation for this class was generated from the following file:

State.h

Public Member Functions

Protected Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ ~IState()

Member Function Documentation

◆ AllocateQubits()

◆ AllProbabilities()

◆ Amplitude()

◆ AmplitudeRaw()

◆ ApplyReset()

◆ Clear()

◆ ClearObservers()

◆ Configure()

◆ DontNotify()

◆ ExpectationValue()

◆ Flush()

◆ GetConfiguration()

◆ GetGatesCounter()

◆ GetMultithreading()

◆ GetNumberOfQubits()

◆ GetSimulationType()

◆ GetType()

◆ IncrementGatesCounter()

◆ Initialize()

◆ InitializeState() [1/3]

◆ InitializeState() [2/3]

◆ InitializeState() [3/3]

◆ IsQcsim()

◆ Measure()

◆ MeasureMany()

◆ MeasureNoCollapse()

◆ MeasureNoCollapseMany()

◆ Notify()

◆ NotifyObservers()

◆ Probabilities()

◆ Probability()

◆ ProjectOnZero()

◆ RegisterObserver()

◆ Reset()

◆ RestoreInternalDestructiveSavedState()

◆ RestoreState()

◆ SampleCounts()

◆ SampleCountsMany()

◆ SaveState()

◆ SaveStateToInternalDestructive()

◆ SetGatesCounter()

◆ SetInitialQubitsMap()

◆ SetLookaheadDepth()

◆ SetLookaheadDepthWithHeuristic()

◆ SetMultithreading()

◆ SetUpcomingGates()

◆ SetUseOptimalMeetingPosition()

◆ SupportsMPSSwapOptimization()

◆ UnregisterObserver()