tntMpsCreateConfig.c

/*
Authors: Sarah Al-Assam, Stephen Clark and Dieter Jaksch
$LastChangedDate$
(c) University of Oxford 2014
*/

/* Include the header for the TNT library */
#include "tntMpsInternal.h"

tntNetwork tntMpsCreateConfig(unsigned L, 
                              const char *config) 
{

    tntNetwork mps;     /* The mps network to create */
    tntNode A;          /* The current node */
    tntComplexArray Aarr;
    unsigned loop;
    unsigned d; /* Dimension of the physical leg */
    tntIntArray qnums_phys, qnums_int; /* Quantum numbers for the physical leg, and for the internal legs (1 internal leg only) */
    unsigned config_length; /* Number of characters in the configuration */
    unsigned bs; /* State for the current site */

    /* Get the dimension of the physical leg */
    if (NULL == tntSysBasisOpGet()) {
        tntErrorPrint("Cannot create wave function using configuration as the basis operator for the system has not yet been set"); /* NO_COVERAGE */
    } else { /* NO_COVERAGE */
        d = tntNodeGetLegDim(tntSysBasisOpGet(),"D");
    }
    
    /* Create the empty network */
    mps = tntNetworkCreate();
    
    /* Get the quantum numbers for the physical leg and initialise internal QNs */
    if (tntSymmTypeGet()) {
        qnums_phys = tntNodeGetQN(tntSysBasisOpGet(), "D");
        qnums_int = tntIntArrayAlloc(tntSymmNumGet());
    }
    
    /* Initialise array for holding node values */
    Aarr = tntComplexArrayAlloc(d);

    /* Find the length of the provided configuration */
    config_length = _tnt_strlen(config);

    /* Keep inserting nodes at the end. */
    for (loop = 0; loop < L; loop++) {

        /* Find the non-zero entry using the character array, and convert the single character to an integer */
        /* If loop is larger than character array, then fill with 0 instead */
        if (loop < config_length) {
            bs = (unsigned) config[loop] - '0';

            /* Check that the basis is valid */
            if (bs > d-1) tntErrorPrint("Invalid configuration %s|The character %d is larger than the physical dimension (%d) allows.",config,bs,d); /* NO_COVERAGE */
                
        } else {
            bs = 0;
        }

        /* Set the value in the array to form the node */
        Aarr.vals[bs].re = 1.0;

        /* Create the node */
        A = tntNodeCreate(&Aarr, "DLR", d);

        /* Insert the node in the network */
        tntNodeInsertAtEnd(A, "L", "R", mps);

        /* Set the array back to all zeros */
        Aarr.vals[bs].re = 0.0;
        
        /* Now set the quantum number information if there are symmetries in the sysem: */
        if (TNT_SYMM_U1 == tntSymmTypeGet()) {
            /* Physical leg is incoming leg and has same information as operator */
            tntNodeSetQN(A,"D",&qnums_phys,TNT_QN_IN);
        
            /* Left leg is incoming leg, and has value = to current total charge */
            tntNodeSetQN(A,"L",&qnums_int,TNT_QN_IN);
            
            /* make the node invariant, this will set QNs on the right internal leg (the only remaining leg that does not have QNs set) as an outgoing leg */
            tntNodeMakeCovariantQN(A);
            
            /* Get the quantum numbers on the leg (freeing previous values first) */
            tntIntArrayFree(&qnums_int);
            qnums_int = tntNodeGetQN(A, "R");
        }

    }

    /* Free the array for holding array values */
    tntComplexArrayFree(&Aarr);
    
    /* Free the qn information if it was used */
    if (TNT_SYMM_U1 == tntSymmTypeGet()) {
        tntIntArrayFree(&qnums_phys);
        tntIntArrayFree(&qnums_int);
    }

    /* return the completed matrix product state */
    return mps;
}