Does not work with QASM Simulator

[cryotheta]

Hi, the code does not seem to work when qasm_simulator is chosen. And leads to the following error:

backend = Aer.get_backend('qasm_simulator')  # use this for QASM simulator

---

QiskitError Traceback (most recent call last)
Input In [13], in <cell line: 5>()
5 for alpha in alphas:
6 objectives[alpha] = Objective(var_form, H, offset, alpha, backend, optimal=optimal_value)
----> 7 optimizer.optimize(m, objectives[alpha].evaluate, initial_point=initial_point)

File ~\Anaconda3\lib\site-packages\qiskit\algorithms\optimizers\scipy_optimizer.py:158, in SciPyOptimizer.optimize(self, num_vars, objective_function, gradient_function, variable_bounds, initial_point)
147 def optimize(
148 self,
149 num_vars,
(...)
153 initial_point=None,
154 ):
155 super().optimize(
156 num_vars, objective_function, gradient_function, variable_bounds, initial_point
157 )
--> 158 result = self.minimize(
159 objective_function, initial_point, gradient_function, variable_bounds
160 )
161 return result.x, result.fun, result.nfev

File ~\Anaconda3\lib\site-packages\qiskit\algorithms\optimizers\scipy_optimizer.py:129, in SciPyOptimizer.minimize(self, fun, x0, jac, bounds)
126 if jac is not None and self._method == "l-bfgs-b":
127 jac = self._wrap_gradient(jac)
--> 129 raw_result = minimize(
130 fun=fun,
131 x0=x0,
132 method=self._method,
133 jac=jac,
134 bounds=bounds,
135 options=self._options,
136 **self._kwargs,
137 )
138 result = OptimizerResult()
139 result.x = raw_result.x

File ~\Anaconda3\lib\site-packages\scipy\optimize_minimize.py:629, in minimize(fun, x0, args, method, jac, hess, hessp, bounds, constraints, tol, callback, options)
626 return _minimize_tnc(fun, x0, args, jac, bounds, callback=callback,
627 **options)
628 elif meth == 'cobyla':
--> 629 return _minimize_cobyla(fun, x0, args, constraints, **options)
630 elif meth == 'slsqp':
631 return _minimize_slsqp(fun, x0, args, jac, bounds,
632 constraints, callback=callback, **options)

File ~\Anaconda3\lib\site-packages\scipy\optimize\cobyla.py:34, in synchronized..wrapper(*args, **kwargs)
31 @functools.wraps(func)
32 def wrapper(*args, **kwargs):
33 with _module_lock:
---> 34 return func(*args, **kwargs)

File ~\Anaconda3\lib\site-packages\scipy\optimize\cobyla.py:260, in _minimize_cobyla(fun, x0, args, constraints, rhobeg, tol, maxiter, disp, catol, **unknown_options)
257 return f
259 info = np.zeros(4, np.float64)
--> 260 xopt, info = _cobyla.minimize(calcfc, m=m, x=np.copy(x0), rhobeg=rhobeg,
261 rhoend=rhoend, iprint=iprint, maxfun=maxfun,
262 dinfo=info)
264 if info[3] > catol:
265 # Check constraint violation
266 info[0] = 4

File ~\Anaconda3\lib\site-packages\scipy\optimize\cobyla.py:252, in _minimize_cobyla..calcfc(x, con)
251 def calcfc(x, con):
--> 252 f = fun(np.copy(x), *args)
253 i = 0
254 for size, c in izip(cons_lengths, constraints):

Input In [12], in Objective.evaluate(self, thetas)
20 job = execute(qc, self.backend)
21 result = job.result()
---> 22 counts = result.get_counts()
24 # evaluate counts
25 probabilities = np.zeros(len(counts))

File ~\Anaconda3\lib\site-packages\qiskit\result\result.py:300, in Result.get_counts(self, experiment)
298 dict_list.append(statevector.Statevector(vec).probabilities_dict(decimals=15))
299 else:
--> 300 raise QiskitError(f'No counts for experiment "{repr(key)}"')
302 # Return first item of dict_list if size is 1
303 if len(dict_list) == 1:

QiskitError: 'No counts for experiment "0"'