Partial trace

Functions for calculating reduced density matrices, creating a new output Qureg. More...

Functions
Qureg	calcPartialTrace (Qureg qureg, int *traceOutQubits, int numTraceQubits)
Qureg	calcReducedDensityMatrix (Qureg qureg, int *retainQubits, int numRetainQubits)

Detailed Description

Functions for calculating reduced density matrices, creating a new output Qureg.

Function Documentation

calcPartialTrace()

Qureg calcPartialTrace	(	Qureg	qureg,
		int *	traceOutQubits,
		int	numTraceQubits )

Note

Documentation for this function or struct is under construction!

Attention

This function's input validation has not yet been tested, so erroneous usage may produce unexpected output. Please use with caution!

Definition at line 368 of file calculations.cpp.

                                                                             {
    validate_quregFields(qureg, __func__);
    validate_quregIsDensityMatrix(qureg, __func__);
    validate_targets(qureg, traceOutQubits, numTraceQubits, __func__);
    validate_quregCanBeReduced(qureg, numTraceQubits, __func__);
 
    // attempt to create reduced Qureg with same deployments as input Qureg
    Qureg out = validateAndCreateCustomQureg(
        qureg.numQubits - numTraceQubits, 
        qureg.isDensityMatrix,  qureg.isDistributed, 
        qureg.isGpuAccelerated, qureg.isMultithreaded, __func__);
 
    // set it to reduced density matrix
    auto targets = util_getVector(traceOutQubits, numTraceQubits);
    localiser_densmatr_partialTrace(qureg, out, targets);
 
    return out;
}

Referenced by calcReducedDensityMatrix(), and TEST_CASE().

calcReducedDensityMatrix()

Qureg calcReducedDensityMatrix	(	Qureg	qureg,
		int *	retainQubits,
		int	numRetainQubits )

Note

Documentation for this function or struct is under construction!

Attention

This function's input validation has not yet been tested, so erroneous usage may produce unexpected output. Please use with caution!

Definition at line 388 of file calculations.cpp.

                                                                                    {
    validate_quregFields(qureg, __func__);
    validate_quregIsDensityMatrix(qureg, __func__);
    validate_targets(qureg, retainQubits, numRetainQubits, __func__);
    validate_quregCanBeReduced(qureg, qureg.numQubits - numRetainQubits, __func__);
 
    auto traceQubits = util_getNonTargetedQubits(retainQubits, numRetainQubits, qureg.numQubits);
 
    // harmlessly re-validates
    return calcPartialTrace(qureg, traceQubits.data(), traceQubits.size());
}

Referenced by TEST_CASE().