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ORNL-QCI / tnqvm

Tensor Network QPU Simulator for Eclipse XACC
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bug in vqe execution #89

Closed amccaskey closed 3 years ago

amccaskey commented 3 years ago

I am observing that the following code does not converge to the correct energy, while it does with the qpp accelerator 

import xacc
xacc.qasm('''
.compiler xasm
.circuit ansatz
.parameters theta
.qbit q
U(q[0], 3.14159,-1.5708,1.5708);
U(q[2], 3.14159,-1.5708,1.5708);
U(q[0], 1.5708,-1.5708,1.5708);
U(q[1], 1.5708,0,3.14159);
U(q[2], 1.5708,0,3.14159);
U(q[3], 1.5708,0,3.14159);
CNOT(q[0], q[1]);
CNOT(q[1], q[2]);
CNOT(q[2], q[3]);
Rz(q[3], theta);
CNOT(q[2], q[3]);
CNOT(q[1], q[2]);
CNOT(q[0], q[1]);
U(q[0], 1.5708,1.5708,4.71239);
U(q[1], 1.5708,0,3.14159);
U(q[2], 1.5708,0,3.14159);
U(q[3], 1.5708,0,3.14159);
''')
ansatz = xacc.getCompiled('ansatz')

qpu = xacc.getAccelerator('tnqvm')
buffer = xacc.qalloc(4)
geom = '''
Na  0.000000   0.0      0.0
H   0.0        0.0  1.914388
'''
fo = [0, 1, 2, 3, 4, 10, 11, 12, 13, 14]
ao = [5, 9, 15, 19]
H = xacc.getObservable('pyscf', {'basis': 'sto-3g', 'geometry': geom,
                                       'frozen-spin-orbitals': fo, 'active-spin-orbitals': ao})
opt = xacc.getOptimizer('nlopt')
vqe = xacc.getAlgorithm('vqe', {
                        'ansatz': ansatz,
                        'accelerator': qpu,
                        'observable': H,
                        'optimizer': opt
                        })
xacc.set_verbose(True)
vqe.execute(buffer)
print('Energy = ', buffer['opt-val'])
print('Opt Angles = ', buffer['opt-params'])