#include "QuEST.h"
#include "QuEST_precision.h"
#include "QuEST_internal.h"
#include "QuEST_validation.h"
#include "QuEST_qasm.h"
#include <stdlib.h>
#include <string.h>

Functions
void	applyDiagonalOp (Qureg qureg, DiagonalOp op)
	Apply a diagonal complex operator, which is possibly non-unitary and non-Hermitian, on the entire `qureg`, More...

void	applyMatrix2 (Qureg qureg, int targetQubit, ComplexMatrix2 u)
	Apply a general 2-by-2 matrix, which may be non-unitary. More...

void	applyMatrix4 (Qureg qureg, int targetQubit1, int targetQubit2, ComplexMatrix4 u)
	Apply a general 4-by-4 matrix, which may be non-unitary. More...

void	applyMatrixN (Qureg qureg, int *targs, int numTargs, ComplexMatrixN u)
	Apply a general N-by-N matrix, which may be non-unitary, on any number of target qubits. More...

void	applyMultiControlledMatrixN (Qureg qureg, int ctrls, int numCtrls, int targs, int numTargs, ComplexMatrixN u)
	Apply a general N-by-N matrix, which may be non-unitary, with additional controlled qubits. More...

void	applyPauliHamil (Qureg inQureg, PauliHamil hamil, Qureg outQureg)
	Modifies `outQureg` to be the result of applying `PauliHamil` (a Hermitian but not necessarily unitary operator) to `inQureg`. More...

void	applyPauliSum (Qureg inQureg, enum pauliOpType allPauliCodes, qreal termCoeffs, int numSumTerms, Qureg outQureg)
	Modifies `outQureg` to be the result of applying the weighted sum of Pauli products (a Hermitian but not necessarily unitary operator) to `inQureg`. More...

void	applyTrotterCircuit (Qureg qureg, PauliHamil hamil, qreal time, int order, int reps)
	Applies a trotterisation of unitary evolution $\exp(-i \, \text{hamil} \, \text{time})$ to `qureg`. More...

qreal	calcDensityInnerProduct (Qureg rho1, Qureg rho2)
	Computes the Hilbert-Schmidt scalar product (which is equivalent to the Frobenius inner product of matrices) of two density matrices `rho1` and `rho2` of equivalent size. More...

Complex	calcExpecDiagonalOp (Qureg qureg, DiagonalOp op)
	Computes the expected value of the diagonal operator `op` for state `qureg`. More...

qreal	calcExpecPauliHamil (Qureg qureg, PauliHamil hamil, Qureg workspace)
	Computes the expected value of `qureg` under Hermitian operator `hamil`. More...

qreal	calcExpecPauliProd (Qureg qureg, int targetQubits, enum pauliOpType pauliCodes, int numTargets, Qureg workspace)
	Computes the expected value of a product of Pauli operators. More...

qreal	calcExpecPauliSum (Qureg qureg, enum pauliOpType allPauliCodes, qreal termCoeffs, int numSumTerms, Qureg workspace)
	Computes the expected value of a sum of products of Pauli operators. More...

qreal	calcFidelity (Qureg qureg, Qureg pureState)
	Calculates the fidelity of `qureg` (a statevector or density matrix) against a reference pure state (necessarily a statevector). More...

qreal	calcHilbertSchmidtDistance (Qureg a, Qureg b)
	Computes the Hilbert Schmidt distance between two density matrices `a` and `b`, defined as the Frobenius norm of the difference between them. More...

Complex	calcInnerProduct (Qureg bra, Qureg ket)
	Computes the inner product $\langle \text{bra} \| \text{ket} \rangle$ of two equal-size state vectors, given by. More...

qreal	calcProbOfOutcome (Qureg qureg, int measureQubit, int outcome)
	Gives the probability of a specified qubit being measured in the given outcome (0 or 1). More...

qreal	calcPurity (Qureg qureg)
	Calculates the purity of a density matrix, by the trace of the density matrix squared. More...

qreal	calcTotalProb (Qureg qureg)
	A debugging function which calculates the probability of the qubits in `qureg` being in any state, which should always be 1 for correctly normalised states (hence returning a real number). More...

void	clearRecordedQASM (Qureg qureg)
	Clear all QASM so far recorded. More...

void	cloneQureg (Qureg targetQureg, Qureg copyQureg)
	Set targetQureg to be a clone of copyQureg. More...

qreal	collapseToOutcome (Qureg qureg, int measureQubit, int outcome)
	Updates `qureg` to be consistent with measuring `measureQubit` in the given `outcome` (0 or 1), and returns the probability of such a measurement outcome. More...

void	compactUnitary (Qureg qureg, int targetQubit, Complex alpha, Complex beta)
	Apply a single-qubit unitary parameterised by two given complex scalars. More...

int	compareStates (Qureg qureg1, Qureg qureg2, qreal precision)
	Return whether two given wavefunctions are equivalent within a given precision Global phase included in equivalence check. More...

void	controlledCompactUnitary (Qureg qureg, int controlQubit, int targetQubit, Complex alpha, Complex beta)
	Apply a controlled unitary (single control, single target) parameterised by two given complex scalars. More...

void	controlledMultiQubitUnitary (Qureg qureg, int ctrl, int *targs, int numTargs, ComplexMatrixN u)
	Apply a general controlled multi-qubit unitary (including a global phase factor). More...

void	controlledNot (Qureg qureg, int controlQubit, int targetQubit)
	Apply the controlled not (single control, single target) gate, also known as the c-X, c-sigma-X, c-Pauli-X and c-bit-flip gate. More...

void	controlledPauliY (Qureg qureg, int controlQubit, int targetQubit)
	Apply the controlled pauliY (single control, single target) gate, also known as the c-Y and c-sigma-Y gate. More...

void	controlledPhaseFlip (Qureg qureg, int idQubit1, int idQubit2)
	Apply the (two-qubit) controlled phase flip gate, also known as the controlled pauliZ gate. More...

void	controlledPhaseShift (Qureg qureg, int idQubit1, int idQubit2, qreal angle)
	Introduce a phase factor $\exp(i \theta)$ on state $\|11\rangle$ of qubits `idQubit1` and `idQubit2`. More...

void	controlledRotateAroundAxis (Qureg qureg, int controlQubit, int targetQubit, qreal angle, Vector axis)
	Applies a controlled rotation by a given angle around a given vector on the Bloch-sphere. More...

void	controlledRotateX (Qureg qureg, int controlQubit, int targetQubit, qreal angle)
	Applies a controlled rotation by a given angle around the X-axis of the Bloch-sphere. More...

void	controlledRotateY (Qureg qureg, int controlQubit, int targetQubit, qreal angle)
	Applies a controlled rotation by a given angle around the Y-axis of the Bloch-sphere. More...

void	controlledRotateZ (Qureg qureg, int controlQubit, int targetQubit, qreal angle)
	Applies a controlled rotation by a given angle around the Z-axis of the Bloch-sphere. More...

void	controlledTwoQubitUnitary (Qureg qureg, int controlQubit, int targetQubit1, int targetQubit2, ComplexMatrix4 u)
	Apply a general controlled two-qubit unitary (including a global phase factor). More...

void	controlledUnitary (Qureg qureg, int controlQubit, int targetQubit, ComplexMatrix2 u)
	Apply a general controlled unitary (single control, single target), which can include a global phase factor. More...

Qureg	createCloneQureg (Qureg qureg, QuESTEnv env)
	Create a new Qureg which is an exact clone of the passed qureg, which can be either a statevector or a density matrix. More...

ComplexMatrixN	createComplexMatrixN (int numQubits)
	Create (dynamically) a square complex matrix which can be passed to the multi-qubit general unitary functions. More...

Qureg	createDensityQureg (int numQubits, QuESTEnv env)
	Create a Qureg for qubits which are represented by a density matrix, and can be in mixed states. More...

DiagonalOp	createDiagonalOp (int numQubits, QuESTEnv env)
	Creates a DiagonalOp representing a diagonal operator on the full Hilbert space of a Qureg. More...

PauliHamil	createPauliHamil (int numQubits, int numSumTerms)
	Create a `PauliHamil` instance, which is a Hamiltonian expressed as a real-weighted sum of products of Pauli operators. More...

PauliHamil	createPauliHamilFromFile (char *fn)
	Create a `PauliHamil` instance, a real-weighted sum of products of Pauli operators, populated with the data in filename `fn`. More...

Qureg	createQureg (int numQubits, QuESTEnv env)
	Create a Qureg object representing a set of qubits which will remain in a pure state. More...

void	destroyComplexMatrixN (ComplexMatrixN m)
	Destroy a ComplexMatrixN instance created with createComplexMatrixN() More...

void	destroyDiagonalOp (DiagonalOp op, QuESTEnv env)
	Destroys a DiagonalOp created with createDiagonalOp(), freeing its memory. More...

void	destroyPauliHamil (PauliHamil h)
	Destroy a `PauliHamil` instance, created with either createPauliHamil() or createPauliHamilFromFile(). More...

void	destroyQureg (Qureg qureg, QuESTEnv env)
	Deallocate a Qureg object representing a set of qubits. More...

Complex	getAmp (Qureg qureg, long long int index)
	Get the complex amplitude at a given index in the state vector. More...

Complex	getDensityAmp (Qureg qureg, long long int row, long long int col)
	Get an amplitude from a density matrix at a given row and column. More...

qreal	getImagAmp (Qureg qureg, long long int index)
	Get the imaginary component of the complex probability amplitude at an index in the state vector. More...

long long int	getNumAmps (Qureg qureg)
	Get the number of probability amplitudes in a qureg object, given by 2^numQubits. More...

int	getNumQubits (Qureg qureg)
	Get the number of qubits in a qureg object. More...

qreal	getProbAmp (Qureg qureg, long long int index)
	Get the probability of a state-vector at an index in the full state vector. More...

int	getQuEST_PREC (void)

qreal	getRealAmp (Qureg qureg, long long int index)
	Get the real component of the complex probability amplitude at an index in the state vector. More...

void	hadamard (Qureg qureg, int targetQubit)
	Apply the single-qubit Hadamard gate. More...

void	initBlankState (Qureg qureg)
	Initialises a qureg to have all-zero-amplitudes. More...

void	initClassicalState (Qureg qureg, long long int stateInd)
	Initialise a set of qubits to the classical state (also known as a "computational basis state") with index `stateInd`. More...

void	initComplexMatrixN (ComplexMatrixN m, qreal re[][1<< m.numQubits], qreal im[][1<< m.numQubits])
	Initialises a ComplexMatrixN instance to have the passed `real` and `imag` values. More...

void	initDebugState (Qureg qureg)
	Initialises `qureg` to be in the un-normalised, non-physical state with with n-th complex amplitude (2n/10 + i(2n+1)/10). More...

void	initDiagonalOp (DiagonalOp op, qreal real, qreal imag)
	Updates the entire DiagonalOp `op` with the given elements, of which there must be 2^`op.numQubits`. More...

void	initPauliHamil (PauliHamil hamil, qreal coeffs, enum pauliOpType codes)
	Initialise a `PauliHamil` instance with the given term coefficients and Pauli codes (one for every qubit in every term). More...

void	initPlusState (Qureg qureg)
	Initialise a set of qubits to the plus state ${\| + \rangle}^{\otimes N} = \frac{1}{\sqrt{2^N}} (\| 0 \rangle + \| 1 \rangle)^{\otimes N}$ (and similarly $\|+\rangle \langle+\|$ for density matrices). More...

void	initPureState (Qureg qureg, Qureg pure)
	Initialise a set of qubits, which can be a state vector or density matrix, to a given pure state. More...

void	initStateFromAmps (Qureg qureg, qreal reals, qreal imags)
	Initialise qureg by specifying the complete statevector. More...

void	initStateFromSingleFile (Qureg *qureg, char filename[200], QuESTEnv env)
	Initialises the wavefunction amplitudes according to those specified in a file. More...

void	initStateOfSingleQubit (Qureg *qureg, int qubitId, int outcome)
	Initialise the state vector of probability amplitudes such that one qubit is set to 'outcome' and all other qubits are in an equal superposition of zero and one. More...

void	initZeroState (Qureg qureg)
	Initialise a set of qubits to the classical zero state ${\| 0 \rangle}^{\otimes N}$ . More...

int	measure (Qureg qureg, int measureQubit)
	Measures a single qubit, collapsing it randomly to 0 or 1. More...

int	measureWithStats (Qureg qureg, int measureQubit, qreal *outcomeProb)
	Measures a single qubit, collapsing it randomly to 0 or 1, and additionally gives the probability of that outcome. More...

void	mixDamping (Qureg qureg, int targetQubit, qreal prob)
	Mixes a density matrix `qureg` to induce single-qubit amplitude damping (decay to 0 state). More...

void	mixDensityMatrix (Qureg combineQureg, qreal otherProb, Qureg otherQureg)
	Modifies combineQureg to become (1-prob)combineProb + prob otherQureg. More...

void	mixDephasing (Qureg qureg, int targetQubit, qreal prob)
	Mixes a density matrix `qureg` to induce single-qubit dephasing noise. More...

void	mixDepolarising (Qureg qureg, int targetQubit, qreal prob)
	Mixes a density matrix `qureg` to induce single-qubit homogeneous depolarising noise. More...

void	mixKrausMap (Qureg qureg, int target, ComplexMatrix2 *ops, int numOps)
	Apply a general single-qubit Kraus map to a density matrix, as specified by at most four Kraus operators, (`ops`). More...

void	mixMultiQubitKrausMap (Qureg qureg, int targets, int numTargets, ComplexMatrixN ops, int numOps)
	Apply a general N-qubit Kraus map to a density matrix, as specified by at most (2N)^2 Kraus operators. More...

void	mixPauli (Qureg qureg, int qubit, qreal probX, qreal probY, qreal probZ)
	Mixes a density matrix `qureg` to induce general single-qubit Pauli noise. More...

void	mixTwoQubitDephasing (Qureg qureg, int qubit1, int qubit2, qreal prob)
	Mixes a density matrix `qureg` to induce two-qubit dephasing noise. More...

void	mixTwoQubitDepolarising (Qureg qureg, int qubit1, int qubit2, qreal prob)
	Mixes a density matrix `qureg` to induce two-qubit homogeneous depolarising noise. More...

void	mixTwoQubitKrausMap (Qureg qureg, int target1, int target2, ComplexMatrix4 *ops, int numOps)
	Apply a general two-qubit Kraus map to a density matrix, as specified by at most sixteen Kraus operators. More...

void	multiControlledMultiQubitUnitary (Qureg qureg, int ctrls, int numCtrls, int targs, int numTargs, ComplexMatrixN u)
	Apply a general multi-controlled multi-qubit unitary (including a global phase factor). More...

void	multiControlledPhaseFlip (Qureg qureg, int *controlQubits, int numControlQubits)
	Apply the multiple-qubit controlled phase flip gate, also known as the multiple-qubit controlled pauliZ gate. More...

void	multiControlledPhaseShift (Qureg qureg, int *controlQubits, int numControlQubits, qreal angle)
	Introduce a phase factor $\exp(i \theta)$ on state $\|1 \dots 1 \rangle$ of the passed qubits. More...

void	multiControlledTwoQubitUnitary (Qureg qureg, int *controlQubits, int numControlQubits, int targetQubit1, int targetQubit2, ComplexMatrix4 u)
	Apply a general multi-controlled two-qubit unitary (including a global phase factor). More...

void	multiControlledUnitary (Qureg qureg, int *controlQubits, int numControlQubits, int targetQubit, ComplexMatrix2 u)
	Apply a general multiple-control single-target unitary, which can include a global phase factor. More...

void	multiQubitUnitary (Qureg qureg, int *targs, int numTargs, ComplexMatrixN u)
	Apply a general multi-qubit unitary (including a global phase factor) with any number of target qubits. More...

void	multiRotatePauli (Qureg qureg, int targetQubits, enum pauliOpType targetPaulis, int numTargets, qreal angle)
	Apply a multi-qubit multi-Pauli rotation on a selected number of qubits. More...

void	multiRotateZ (Qureg qureg, int *qubits, int numQubits, qreal angle)
	Apply a multi-qubit Z rotation on a selected number of qubits. More...

void	multiStateControlledUnitary (Qureg qureg, int controlQubits, int controlState, int numControlQubits, int targetQubit, ComplexMatrix2 u)
	Apply a general multiple-control, conditioned on a specific bit sequence, single-target unitary, which can include a global phase factor. More...

void	pauliX (Qureg qureg, int targetQubit)
	Apply the single-qubit Pauli-X (also known as the X, sigma-X, NOT or bit-flip) gate. More...

void	pauliY (Qureg qureg, int targetQubit)
	Apply the single-qubit Pauli-Y (also known as the Y or sigma-Y) gate. More...

void	pauliZ (Qureg qureg, int targetQubit)
	Apply the single-qubit Pauli-Z (also known as the Z, sigma-Z or phase-flip) gate. More...

void	phaseShift (Qureg qureg, int targetQubit, qreal angle)
	Shift the phase between $\|0\rangle$ and $\|1\rangle$ of a single qubit by a given angle. More...

void	printRecordedQASM (Qureg qureg)
	Print recorded QASM to stdout. More...

void	reportPauliHamil (PauliHamil hamil)
	Print the `PauliHamil` to screen. More...

void	reportStateToScreen (Qureg qureg, QuESTEnv env, int reportRank)
	Print the current state vector of probability amplitudes for a set of qubits to standard out. More...

void	rotateAroundAxis (Qureg qureg, int rotQubit, qreal angle, Vector axis)
	Rotate a single qubit by a given angle around a given Vector on the Bloch-sphere. More...

void	rotateX (Qureg qureg, int targetQubit, qreal angle)
	Rotate a single qubit by a given angle around the X-axis of the Bloch-sphere. More...

void	rotateY (Qureg qureg, int targetQubit, qreal angle)
	Rotate a single qubit by a given angle around the Y-axis of the Bloch-sphere. More...

void	rotateZ (Qureg qureg, int targetQubit, qreal angle)
	Rotate a single qubit by a given angle around the Z-axis of the Bloch-sphere (also known as a phase shift gate). More...

void	setAmps (Qureg qureg, long long int startInd, qreal reals, qreal imags, long long int numAmps)
	Overwrites a subset of the amplitudes in `qureg`, with those passed in `reals` and `imags`. More...

void	setDensityAmps (Qureg qureg, qreal reals, qreal imags)
	Set elements in the underlying state vector represenation of a density matrix. More...

void	setDiagonalOpElems (DiagonalOp op, long long int startInd, qreal real, qreal imag, long long int numElems)
	Modifies a subset (starting at index `startInd`) of the elements in DiagonalOp `op` with the given elements, of which there are `numElems`. More...

void	setWeightedQureg (Complex fac1, Qureg qureg1, Complex fac2, Qureg qureg2, Complex facOut, Qureg out)
	Modifies qureg `out` to the result of (`facOut` `out` + `fac1` `qureg1` + `fac2` `qureg2`), imposing no constraints on normalisation. More...

void	sGate (Qureg qureg, int targetQubit)
	Apply the single-qubit S gate. More...

void	sqrtSwapGate (Qureg qureg, int qb1, int qb2)
	Performs a sqrt SWAP gate between `qubit1` and `qubit2`. More...

void	startRecordingQASM (Qureg qureg)
	Enable QASM recording. More...

void	stopRecordingQASM (Qureg qureg)
	Disable QASM recording. More...

void	swapGate (Qureg qureg, int qb1, int qb2)
	Performs a SWAP gate between `qubit1` and `qubit2`. More...

void	syncDiagonalOp (DiagonalOp op)
	Copy the elements in DiagonalOp `op.real` and `op.imag` to the persisent GPU memory. More...

void	tGate (Qureg qureg, int targetQubit)
	Apply the single-qubit T gate. More...

void	twoQubitUnitary (Qureg qureg, int targetQubit1, int targetQubit2, ComplexMatrix4 u)
	Apply a general two-qubit unitary (including a global phase factor). More...

void	unitary (Qureg qureg, int targetQubit, ComplexMatrix2 u)
	Apply a general single-qubit unitary (including a global phase factor). More...

void	writeRecordedQASMToFile (Qureg qureg, char *filename)
	Writes recorded QASM to a file, throwing an error if inaccessible. More...

Detailed Description

Implements the QuEST.h API (and some debugging functions) in a hardware-agnostic way, for both pure and mixed states. These functions mostly wrap hardware-specific functions, and should never call eachother.

Density matrices rho of N qubits are flattened to appear as state-vectors |s> of 2N qubits. Operations U rho U^dag are implemented as U^* U |s> and make use of the pure state backend, and often don't need to explicitly compute U^*.

Author: Tyson Jones (architecture, validation, qasm, density matrices); Ania Brown (setDensityAmps()); Balint Koczor (Kraus maps, calcDensityInnerProduct()); Nicolas Vogt of HQS (one-qubit damping)

Definition in file QuEST.c.

Function Documentation

◆ compareStates()

int compareStates	(	Qureg	mq1,
		Qureg	mq2,
		qreal	precision
	)

Return whether two given wavefunctions are equivalent within a given precision Global phase included in equivalence check.

For debugging purposes.

Definition at line 1303 of file QuEST.c.

                                                                {
     validateMatchingQuregDims(qureg1, qureg2, __func__);
     return statevec_compareStates(qureg1, qureg2, precision);
 }

References statevec_compareStates(), and validateMatchingQuregDims().

◆ getQuEST_PREC()

int getQuEST_PREC ( void )

Definition at line 1339 of file QuEST.c.

                          {
   return sizeof(qreal)/4;
 }

References qreal.

◆ initStateFromSingleFile()

void initStateFromSingleFile	(	Qureg *	qureg,
		char	filename[200],
		QuESTEnv	env
	)

Initialises the wavefunction amplitudes according to those specified in a file.

For debugging purpsoses

Definition at line 1312 of file QuEST.c.

                                                                              {
     int success = statevec_initStateFromSingleFile(qureg, filename, env);
     validateFileOpened(success, filename, __func__);
 }

References statevec_initStateFromSingleFile(), and validateFileOpened().

◆ initStateOfSingleQubit()

void initStateOfSingleQubit	(	Qureg *	qureg,
		int	qubitId,
		int	outcome
	)

Initialise the state vector of probability amplitudes such that one qubit is set to 'outcome' and all other qubits are in an equal superposition of zero and one.

Parameters

[in,out]	qureg	object representing the set of qubits to be initialised
[in]	qubitId	id of qubit to set to state 'outcome'
[in]	outcome	value of qubit 'qubitId' to set

Definition at line 1317 of file QuEST.c.

                                                                     {
     validateStateVecQureg(*qureg, __func__);
     validateTarget(*qureg, qubitId, __func__);
     validateOutcome(outcome, __func__);
     statevec_initStateOfSingleQubit(qureg, qubitId, outcome);
 }

References statevec_initStateOfSingleQubit(), validateOutcome(), validateStateVecQureg(), and validateTarget().

◆ setDensityAmps()

void setDensityAmps	(	Qureg	qureg,
		qreal *	reals,
		qreal *	imags
	)

Set elements in the underlying state vector represenation of a density matrix.

Not exposed in the public API as this requires an understanding of how the state vector is used to represent a density matrix. Currently can only be used to set all amps.

Definition at line 790 of file QuEST.c.

                                                              {
     long long int numAmps = qureg.numAmpsTotal; 
     statevec_setAmps(qureg, 0, reals, imags, numAmps);
     
     qasm_recordComment(qureg, "Here, some amplitudes in the density matrix were manually edited.");
 }

References Qureg::numAmpsTotal, qasm_recordComment(), and statevec_setAmps().