Class Quantum4JBackend

java.lang.Object

org.episteme.natural.physics.quantum.backends.Quantum4JBackend

All Implemented Interfaces:

AlgorithmProvider, Backend, ComputeBackend, QuantumAlgorithmProvider, QuantumBackend

@AutoService({AlgorithmProvider.class,QuantumBackend.class,ComputeBackend.class,Backend.class})
public class Quantum4JBackend
extends Object
implements QuantumBackend, QuantumAlgorithmProvider

Quantum4J backend implementation for Episteme.

Nested Class Summary

Nested classes/interfaces inherited from interface QuantumBackend

QuantumBackend.QuantumCircuit, QuantumBackend.QuantumResult

Constructor Summary

Constructors

Constructor	Description
Quantum4JBackend()

Method Summary

Modifier and Type	Method	Description
QuantumBackend.QuantumCircuit	createCircuit(int q, int c)	Creates a new quantum circuit.
ExecutionContext	createContext()	Creates an execution context for running operations.
Map<String,Integer>	execute(QuantumBackend.QuantumCircuit circuit)	Executes a quantum circuit on a simulator with default 1024 shots.
QuantumBackend.QuantumResult	executeHardware(QuantumBackend.QuantumCircuit c, int s, String b)	Executes a quantum circuit on real quantum hardware.
QuantumBackend.QuantumResult	executeSimulator(QuantumBackend.QuantumCircuit circuit, int shots)	Executes a quantum circuit on a simulator.
HardwareAccelerator	getAcceleratorType()	Returns the type of hardware accelerator used by this backend.
String[]	getAvailableBackends()	Returns available quantum backends (simulators and hardware).
Map<String,Object>	getBackendInfo(String b)	Returns backend information (num_qubits, connectivity, etc.).
String	getDescription()	Returns a description of the backend.
String	getId()	Returns the unique identifier for this backend (e.g., "javafx", "jmol", "cuda").
String	getName()	Returns the display name for UI presentation.
int	getPriority()	Returns the priority for auto-selection (higher = preferred).
String	getStatusMessage()	Returns a human-readable status message for this backend.
QuantumBackend.QuantumResult	groverSearch(QuantumBackend.QuantumCircuit oracle, int numQubits)	Performs Grover's search algorithm.
boolean	isAvailable()	Checks if this backend is currently available (libraries loaded, etc.).
QuantumBackend.QuantumCircuit	matrixToUnitary(Matrix<Complex> m)	Converts a classical matrix to a quantum unitary operator.
QuantumBackend.QuantumResult	qaoa(Matrix<Complex> h, int l)	Performs Quantum Approximate Optimization Algorithm (QAOA).
double	quantumPhaseEstimation(Matrix<Complex> u, Vector<Complex> e, int p)	Performs Quantum Phase Estimation (QPE).
int[]	shorFactor(int N)	Performs Shor's factoring algorithm.
void	shutdown()	Called when the application is shutting down or the backend is being replaced.
Matrix<Complex>	stateTomography(QuantumBackend.QuantumCircuit c, int s)	Performs quantum state tomography to reconstruct a density matrix.
double	vqe(Matrix<Complex> h, QuantumBackend.QuantumCircuit a, String o)	Performs Variational Quantum Eigensolver (VQE) to find ground state energy.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface AlgorithmProvider

description, getMetadata, score

Methods inherited from interface Backend

getAlgorithmProviders, isExplicitlyDisabled

Methods inherited from interface ComputeBackend

createBackend, supportsComplexNumbers, supportsFloatingPoint, supportsParallelOps

Methods inherited from interface QuantumAlgorithmProvider

getAlgorithmType

Methods inherited from interface QuantumBackend

getType

Constructor Details

Quantum4JBackend

public Quantum4JBackend()

Method Details

getId

public String getId()

Description copied from interface: Backend

Returns the unique identifier for this backend (e.g., "javafx", "jmol", "cuda").

Specified by:

getId in interface Backend

Specified by:

getId in interface ComputeBackend

getName

public String getName()

Description copied from interface: Backend

Returns the display name for UI presentation.

Specified by:

getName in interface AlgorithmProvider

Specified by:

getName in interface Backend

Specified by:

getName in interface QuantumAlgorithmProvider

getDescription

public String getDescription()

Description copied from interface: Backend

Returns a description of the backend.

Specified by:

getDescription in interface Backend

Specified by:

getDescription in interface ComputeBackend

getPriority

public int getPriority()

Description copied from interface: Backend

Returns the priority for auto-selection (higher = preferred). Used when multiple backends are available.

Specified by:

getPriority in interface AlgorithmProvider

Specified by:

getPriority in interface Backend

isAvailable

public boolean isAvailable()

Description copied from interface: Backend

Checks if this backend is currently available (libraries loaded, etc.).

Default implementation checks Backend.isExplicitlyDisabled() and returns false if it is.

Specified by:

isAvailable in interface AlgorithmProvider

Specified by:

isAvailable in interface Backend

Specified by:

isAvailable in interface QuantumBackend

getStatusMessage

public String getStatusMessage()

Description copied from interface: Backend

Returns a human-readable status message for this backend. Useful for debugging "Unavailable" states.

Specified by:

getStatusMessage in interface Backend

Returns:

status message (e.g., "Ready", "Native library missing", etc.)

shutdown

public void shutdown()

Description copied from interface: Backend

Called when the application is shutting down or the backend is being replaced. Use this to release hardware resources, close file handles, or stop background threads.

Specified by:

shutdown in interface AlgorithmProvider

Specified by:

shutdown in interface Backend

createContext

public ExecutionContext createContext()

Description copied from interface: ComputeBackend

Creates an execution context for running operations.

The context should be used within a try-with-resources block to ensure proper cleanup of resources.

Specified by:

createContext in interface ComputeBackend

Returns:

new execution context

execute

public Map<String,Integer> execute(QuantumBackend.QuantumCircuit circuit)

Description copied from interface: QuantumBackend

Executes a quantum circuit on a simulator with default 1024 shots.

Specified by:

execute in interface QuantumBackend

executeSimulator

public QuantumBackend.QuantumResult executeSimulator(QuantumBackend.QuantumCircuit circuit,
 int shots)

Description copied from interface: QuantumBackend

Executes a quantum circuit on a simulator.

Specified by:

executeSimulator in interface QuantumBackend

createCircuit

public QuantumBackend.QuantumCircuit createCircuit(int q,
 int c)

Description copied from interface: QuantumBackend

Creates a new quantum circuit.

Specified by:

createCircuit in interface QuantumBackend

executeHardware

public QuantumBackend.QuantumResult executeHardware(QuantumBackend.QuantumCircuit c,
 int s,
 String b)

Description copied from interface: QuantumBackend

Executes a quantum circuit on real quantum hardware.

Specified by:

executeHardware in interface QuantumBackend

vqe

public double vqe(Matrix<Complex> h,
 QuantumBackend.QuantumCircuit a,
 String o)

Description copied from interface: QuantumAlgorithmProvider

Performs Variational Quantum Eigensolver (VQE) to find ground state energy.

Specified by:

vqe in interface QuantumAlgorithmProvider

Parameters:

h - Hamiltonian matrix

a - Parameterized quantum circuit

o - Classical optimizer ("COBYLA", "SPSA", etc.)

Returns:

Ground state energy

qaoa

public QuantumBackend.QuantumResult qaoa(Matrix<Complex> h,
 int l)

Description copied from interface: QuantumAlgorithmProvider

Performs Quantum Approximate Optimization Algorithm (QAOA).

Specified by:

qaoa in interface QuantumAlgorithmProvider

Parameters:

h - Cost Hamiltonian for the optimization problem

l - Number of QAOA layers (p parameter)

Returns:

Optimal parameters and final state

quantumPhaseEstimation

public double quantumPhaseEstimation(Matrix<Complex> u,
 Vector<Complex> e,
 int p)

Description copied from interface: QuantumAlgorithmProvider

Performs Quantum Phase Estimation (QPE).

Specified by:

quantumPhaseEstimation in interface QuantumAlgorithmProvider

Parameters:

u - Unitary operator

e - Initial eigenstate

p - Number of precision qubits

Returns:

Estimated phase

groverSearch

public QuantumBackend.QuantumResult groverSearch(QuantumBackend.QuantumCircuit oracle,
 int numQubits)

Description copied from interface: QuantumAlgorithmProvider

Performs Grover's search algorithm.

Specified by:

groverSearch in interface QuantumAlgorithmProvider

Parameters:

oracle - Oracle function (marks solution states)

numQubits - Number of qubits in search space

Returns:

Measurement result (solution state)

shorFactor

public int[] shorFactor(int N)

Description copied from interface: QuantumAlgorithmProvider

Performs Shor's factoring algorithm.

Specified by:

shorFactor in interface QuantumAlgorithmProvider

Parameters:

N - Number to factor

Returns:

Factors of N

matrixToUnitary

public QuantumBackend.QuantumCircuit matrixToUnitary(Matrix<Complex> m)

Description copied from interface: QuantumAlgorithmProvider

Converts a classical matrix to a quantum unitary operator.

Specified by:

matrixToUnitary in interface QuantumAlgorithmProvider

stateTomography

public Matrix<Complex> stateTomography(QuantumBackend.QuantumCircuit c,
 int s)

Description copied from interface: QuantumAlgorithmProvider

Performs quantum state tomography to reconstruct a density matrix.

Specified by:

stateTomography in interface QuantumAlgorithmProvider

getAvailableBackends

public String[] getAvailableBackends()

Description copied from interface: QuantumBackend

Returns available quantum backends (simulators and hardware).

Specified by:

getAvailableBackends in interface QuantumBackend

getBackendInfo

public Map<String,Object> getBackendInfo(String b)

Description copied from interface: QuantumBackend

Returns backend information (num_qubits, connectivity, etc.).

Specified by:

getBackendInfo in interface QuantumBackend

getAcceleratorType

public HardwareAccelerator getAcceleratorType()

Description copied from interface: ComputeBackend

Returns the type of hardware accelerator used by this backend.

Specified by:

getAcceleratorType in interface ComputeBackend

Returns:

the accelerator type