Refactor QubitWaveFunction, add support for Numpy array backed dense representation

src/tequila/apps/unary_state_prep.py

@@ -89,7 +89,6 @@ def __init__(self, target_space: typing.List[BitString], max_repeat: int = 100,
         simulator.convert_to_numpy = False
         variables = None # {k:k.name.evalf() for k in self._abstract_circuit.extract_variables()}
         wfn = simulator.simulate(initial_state=BitString.from_int(0, nbits=self.n_qubits), variables=variables)
-        wfn.n_qubits = self._n_qubits
         equations = []
         for k in target_space:
             equations.append(wfn[k] - abstract_coefficients[k])
@@ -174,7 +173,7 @@ def __call__(self, wfn: QubitWaveFunction) -> QCircuit:
         :return:
         """
         try:
-            assert (len(wfn) == len(self._target_space))
+            assert wfn.length() == len(self._target_space)
             for key in wfn.keys():
                 try:
                     assert (key in self._target_space)

src/tequila/hamiltonian/paulis.py

@@ -256,7 +256,7 @@ def Projector(wfn, threshold=0.0, n_qubits=None) -> QubitHamiltonian:
 
     """
 
-    wfn = QubitWaveFunction(state=wfn, n_qubits=n_qubits)
+    wfn = QubitWaveFunction.convert_from(n_qubits, wfn)
 
     H = QubitHamiltonian.zero()
     for k1, v1 in wfn.items():
@@ -304,8 +304,9 @@ def KetBra(ket: QubitWaveFunction, bra: QubitWaveFunction, hermitian: bool = Fal
 
     """
     H = QubitHamiltonian.zero()
-    ket = QubitWaveFunction(state=ket, n_qubits=n_qubits)
-    bra = QubitWaveFunction(state=bra, n_qubits=n_qubits)
+
+    ket = QubitWaveFunction.convert_from(n_qubits, ket)
+    bra = QubitWaveFunction.convert_from(n_qubits, bra)
 
     for k1, v1 in bra.items():
         for k2, v2 in ket.items():

src/tequila/quantumchemistry/encodings.py

@@ -128,9 +128,9 @@ def map_state(self, state: list, *args, **kwargs) -> list:
         fop = openfermion.FermionOperator(string, 1.0)
         op = self(fop)
         from tequila.wavefunction.qubit_wavefunction import QubitWaveFunction
-        wfn = QubitWaveFunction.from_int(0, n_qubits=n_qubits)
+        wfn = QubitWaveFunction.from_basis_state(n_qubits, 0)
         wfn = wfn.apply_qubitoperator(operator=op)
-        assert (len(wfn.keys()) == 1)
+        assert wfn.length() == 1
         key = list(wfn.keys())[0].array
         return key
 

src/tequila/simulators/simulator_api.py

@@ -49,7 +49,7 @@
     HAS_QISKIT_GPU = True
     INSTALLED_SIMULATORS["qiskit_gpu"] = BackendTypes(BackendCircuitQiskitGpu, BackendExpectationValueQiskitGpu)
     INSTALLED_SAMPLERS["qiskit_gpu"] = BackendTypes(BackendCircuitQiskitGpu, BackendExpectationValueQiskitGpu)
-    from tequila.simulators.simulator_qiskit_gpu import HAS_NOISE as HAS_QISKIT_GPU_NOISE
+    from tequila.simulators.simulator_qiskit import HAS_NOISE as HAS_QISKIT_GPU_NOISE
     if HAS_QISKIT_GPU_NOISE:
         INSTALLED_NOISE_SAMPLERS["qiskit_gpu"] = BackendTypes(BackendCircuitQiskitGpu, BackendExpectationValueQiskitGpu)
 except (ImportError, DistributionNotFound):
@@ -363,7 +363,7 @@ def compile_circuit(abstract_circuit: 'QCircuit',
     return CircType(abstract_circuit=abstract_circuit, variables=variables, noise=noise, device=device, *args, **kwargs)
 
 
-def simulate(objective: typing.Union['Objective', 'QCircuit','QTensor'],
+def simulate(objective: typing.Union['Objective', 'QCircuit', 'QTensor'],
              variables: Dict[Union[Variable, Hashable], RealNumber] = None,
              samples: int = None,
              backend: str = None,
@@ -407,7 +407,7 @@ def simulate(objective: typing.Union['Objective', 'QCircuit','QTensor'],
                 objective.extract_variables()))
 
     compiled_objective = compile(objective=objective, samples=samples, variables=variables, backend=backend,
-                                 noise=noise,device=device, *args, **kwargs)
+                                 noise=noise, device=device, *args, **kwargs)
 
     return compiled_objective(variables=variables, samples=samples, *args, **kwargs)
 

src/tequila/simulators/simulator_base.py

@@ -352,7 +352,7 @@ def simulate(self, variables, initial_state=0, *args, **kwargs) -> QubitWaveFunc
         if isinstance(initial_state, BitString):
             initial_state = initial_state.integer
         if isinstance(initial_state, QubitWaveFunction):
-            if len(initial_state.keys()) != 1:
+            if initial_state.length() != 1:
                 raise TequilaException("only product states as initial states accepted")
             initial_state = list(initial_state.keys())[0].integer
 
@@ -371,7 +371,7 @@ def simulate(self, variables, initial_state=0, *args, **kwargs) -> QubitWaveFunc
                                   **kwargs)
 
         if keymap_required:
-            result.apply_keymap(keymap=keymap, initial_state=initial_state)
+            result = QubitWaveFunction.from_wavefunction(result, keymap, n_qubits=len(all_qubits), initial_state=initial_state)
 
         return result
 

src/tequila/simulators/simulator_cirq.py

@@ -173,7 +173,7 @@ def do_simulate(self, variables, initial_state=0, *args, **kwargs) -> QubitWaveF
         simulator = cirq.Simulator()
         backend_result = simulator.simulate(program=self.circuit, param_resolver=self.resolver,
                                             initial_state=initial_state)
-        return QubitWaveFunction.from_array(arr=backend_result.final_state_vector, numbering=self.numbering)
+        return QubitWaveFunction.from_array(array=backend_result.final_state_vector, numbering=self.numbering)
 
     def convert_measurements(self, backend_result: cirq.Result) -> QubitWaveFunction:
         """
@@ -186,18 +186,18 @@ def convert_measurements(self, backend_result: cirq.Result) -> QubitWaveFunction
         Returns
         -------
         QubitWaveFunction:
-            the result of sampling, as a tequila QubitWavefunction.
+            the result of sampling, as a tequila QubitWaveFunction.
 
         """
         assert (len(backend_result.measurements) == 1)
         for key, value in backend_result.measurements.items():
-            counter = QubitWaveFunction()
+            counter = QubitWaveFunction(self.n_qubits, self.numbering)
             for sample in value:
                 binary = BitString.from_array(array=sample.astype(int))
-                if binary in counter._state:
-                    counter._state[binary] += 1
+                if binary in counter.keys():
+                    counter[binary] += 1
                 else:
-                    counter._state[binary] = 1
+                    counter[binary] = 1
             return counter
 
     def do_sample(self, samples, circuit, *args, **kwargs) -> QubitWaveFunction:

src/tequila/simulators/simulator_pyquil.py

@@ -439,7 +439,7 @@ def do_simulate(self, variables, initial_state, *args, **kwargs):
             if val > 0:
                 iprep += pyquil.gates.X(i)
         backend_result = simulator.wavefunction(iprep + self.circuit, memory_map=self.resolver)
-        return QubitWaveFunction.from_array(arr=backend_result.amplitudes, numbering=self.numbering)
+        return QubitWaveFunction.from_array(array=backend_result.amplitudes, numbering=self.numbering)
 
     def do_sample(self, samples, circuit, *args, **kwargs) -> QubitWaveFunction:
         """
@@ -495,7 +495,7 @@ def string_to_array(s):
                     listing.append(int(letter))
             return listing
 
-        result = QubitWaveFunction()
+        result = QubitWaveFunction(self.n_qubits, self.numbering)
         bit_dict = {}
         for b in backend_result:
             try:
@@ -505,7 +505,7 @@ def string_to_array(s):
 
         for k, v in bit_dict.items():
             arr = string_to_array(k)
-            result._state[BitString.from_array(arr)] = v
+            result[BitString.from_array(arr)] = v
         return result
 
     def no_translation(self, abstract_circuit):

src/tequila/simulators/simulator_qibo.py

@@ -356,20 +356,20 @@ def do_simulate(self, variables, initial_state=None, *args, **kwargs):
         n_qubits = max(self.highest_qubit + 1, self.n_qubits, self.abstract_circuit.max_qubit() + 1)
         if initial_state is not None:
             if isinstance(initial_state, (int, np.int64)):
-                wave = QubitWaveFunction.from_int(i=initial_state, n_qubits=n_qubits)
+                wave = QubitWaveFunction.from_basis_state(n_qubits, initial_state, self.numbering)
             elif isinstance(initial_state, str):
-                wave = QubitWaveFunction.from_string(string=initial_state).to_array()
+                wave = QubitWaveFunction.from_string(initial_state, self.numbering).to_array()
             elif isinstance(initial_state, QubitWaveFunction):
                 wave = initial_state
             elif isinstance(initial_state,np.ndarray):
-                wave = QubitWaveFunction.from_array(initial_state)
+                wave = QubitWaveFunction.from_array(initial_state, self.numbering)
             else:
                 raise TequilaQiboException('could not understand initial state of type {}'.format(type(initial_state)))
             state = wave.to_array()
             result = self.circuit(state)
         else:
             result = self.circuit()
-        back= QubitWaveFunction.from_array(arr=result.numpy())
+        back= QubitWaveFunction.from_array(result.numpy(), self.numbering)
         return back
 
     def simulate(self, variables, initial_state=0, *args, **kwargs) -> QubitWaveFunction:
@@ -398,7 +398,7 @@ def simulate(self, variables, initial_state=0, *args, **kwargs) -> QubitWaveFunc
         if isinstance(initial_state, BitString):
             initial_state = initial_state.integer
         if isinstance(initial_state, QubitWaveFunction):
-            if len(initial_state.keys()) != 1:
+            if initial_state.length() != 1:
                 return self.do_simulate(variables=variables,initial_state=initial_state, *args, **kwargs)
             initial_state = list(initial_state.keys())[0].integer
         if isinstance(initial_state,np.ndarray):
@@ -426,19 +426,18 @@ def convert_measurements(self, backend_result, target_qubits=None) -> QubitWaveF
             results transformed to tequila native QubitWaveFunction
         """
 
-        result = QubitWaveFunction()
+        result = QubitWaveFunction(self.n_qubits, self.numbering)
         # todo there are faster ways
 
         for k, v in backend_result.frequencies(binary=True).items():
             converted_key = BitString.from_bitstring(other=BitString.from_binary(binary=k))
-            result._state[converted_key] = v
-
+            result[converted_key] = v
 
         if target_qubits is not None:
             mapped_target = [self.qubit_map[q].number for q in target_qubits]
             mapped_full = [self.qubit_map[q].number for q in self.abstract_qubits]
             keymap = KeyMapRegisterToSubregister(subregister=mapped_target, register=mapped_full)
-            result = result.apply_keymap(keymap=keymap)
+            result = QubitWaveFunction.from_wavefunction(result, keymap, len(mapped_target))
 
         return result
 
@@ -521,21 +520,20 @@ def do_sample(self, samples, circuit, noise_model=None, initial_state=None, *arg
         n_qubits = max(self.highest_qubit + 1, self.n_qubits, self.abstract_circuit.max_qubit() + 1)
         if initial_state is not None:
             if isinstance(initial_state, int):
-                wave=QubitWaveFunction.from_int(i=initial_state, n_qubits=n_qubits)
+                wave = QubitWaveFunction.from_basis_state(n_qubits, initial_state, self.numbering)
             elif isinstance(initial_state, str):
-                wave = QubitWaveFunction.from_string(string=initial_state).to_array()
+                wave = QubitWaveFunction.from_string(initial_state, self.numbering).to_array()
             elif isinstance(initial_state, QubitWaveFunction):
                 wave = initial_state
-            elif isinstance(initial_state,np.ndarray):
-                wave = QubitWaveFunction.from_array(arr=initial_state, n_qubits=n_qubits)  # silly but necessary
+            elif isinstance(initial_state, np.ndarray):
+                wave = QubitWaveFunction.from_array(initial_state, self.numbering)  # silly but necessary
             else:
                 raise TequilaQiboException('received an unusable initial state of type {}'.format(type(initial_state)))
-            state=wave.to_array()
-            result = circuit(state,nshots=samples)
+            state = wave.to_array()
+            result = circuit(state, nshots=samples)
         else:
             result = circuit(nshots=samples)
 
-
         back = self.convert_measurements(backend_result=result)
         return back
 

src/tequila/simulators/simulator_qiskit.py

@@ -300,8 +300,7 @@ def do_simulate(self, variables, initial_state=0, *args, **kwargs) -> QubitWaveF
 
         if initial_state != 0:
             state = np.zeros(2 ** self.n_qubits)
-            initial_state = reverse_int_bits(initial_state, self.n_qubits)
-            state[initial_state] = 1.0
+            state[reverse_int_bits(initial_state, self.n_qubits)] = 1.0
             init_circuit = qiskit.QuantumCircuit(self.q, self.c)
             init_circuit.set_statevector(state)
             circuit = init_circuit.compose(circuit)
@@ -310,7 +309,7 @@ def do_simulate(self, variables, initial_state=0, *args, **kwargs) -> QubitWaveF
 
         backend_result = qiskit_backend.run(circuit, optimization_level=optimization_level).result()
 
-        return QubitWaveFunction.from_array(arr=backend_result.get_statevector(circuit), numbering=self.numbering)
+        return QubitWaveFunction.from_array(array=backend_result.get_statevector(circuit).data, numbering=self.numbering)
 
     def do_sample(self, circuit: qiskit.QuantumCircuit, samples: int, read_out_qubits, *args,
                   **kwargs) -> QubitWaveFunction:
@@ -394,16 +393,17 @@ def convert_measurements(self, backend_result, target_qubits=None) -> QubitWaveF
             measurements converted into wave function form.
         """
         qiskit_counts = backend_result.result().get_counts()
-        result = QubitWaveFunction()
+        result = QubitWaveFunction(self.n_qubits, self.numbering)
         # todo there are faster ways
         for k, v in qiskit_counts.items():
-            converted_key = BitString.from_bitstring(other=BitStringLSB.from_binary(binary=k))
-            result._state[converted_key] = v
+            # Qiskit uses LSB bitstrings, but from_binary expects MSB
+            converted_key = BitString.from_binary(k[::-1])
+            result[converted_key] = v
         if target_qubits is not None:
             mapped_target = [self.qubit_map[q].number for q in target_qubits]
             mapped_full = [self.qubit_map[q].number for q in self.abstract_qubits]
             keymap = KeyMapRegisterToSubregister(subregister=mapped_target, register=mapped_full)
-            result = result.apply_keymap(keymap=keymap)
+            result = QubitWaveFunction.from_wavefunction(result, keymap, n_qubits=len(target_qubits))
 
         return result
 

src/tequila/simulators/simulator_qlm.py

@@ -395,10 +395,10 @@ def do_simulate(self, variables, initial_state=0, *args, **kwargs) -> QubitWaveF
         if MY_QLM:
             result = PyLinalg().submit(job)
             statevector = get_statevector(result)
-            return QubitWaveFunction.from_array(arr=statevector, numbering=self.numbering)
+            return QubitWaveFunction.from_array(array=statevector, numbering=self.numbering)
 
         result = LinAlg().submit(job)
-        return QubitWaveFunction.from_array(arr=result.statevector, numbering=self.numbering)
+        return QubitWaveFunction.from_array(array=result.statevector, numbering=self.numbering)
 
     def update_variables(self, variables):
         """
@@ -431,7 +431,7 @@ def convert_measurements(self, backend_result) -> QubitWaveFunction:
         QubitWaveFunction:
             measurements converted into wave function form.
         """
-        result = QubitWaveFunction()
+        result = QubitWaveFunction(self.n_qubits, self.numbering)
         shots = int(backend_result.meta_data["nbshots"])
         nbits = backend_result[0].qregs[0].length
         for sample in backend_result:

src/tequila/simulators/simulator_qulacs.py

@@ -3,7 +3,7 @@
 import warnings
 
 from tequila import TequilaException, TequilaWarning
-from tequila.utils.bitstrings import BitNumbering, BitString, BitStringLSB
+from tequila.utils.bitstrings import BitNumbering, BitString, BitStringLSB, reverse_int_bits
 from tequila.wavefunction.qubit_wavefunction import QubitWaveFunction
 from tequila.simulators.simulator_base import BackendCircuit, BackendExpectationValue, QCircuit, change_basis
 from tequila.utils.keymap import KeyMapRegisterToSubregister
@@ -149,11 +149,10 @@ def do_simulate(self, variables, initial_state, *args, **kwargs):
             QubitWaveFunction representing result of the simulation.
         """
         state = self.initialize_state(self.n_qubits)
-        lsb = BitStringLSB.from_int(initial_state, nbits=self.n_qubits)
-        state.set_computational_basis(BitString.from_binary(lsb.binary).integer)
+        state.set_computational_basis(reverse_int_bits(initial_state, self.n_qubits))
         self.circuit.update_quantum_state(state)
 
-        wfn = QubitWaveFunction.from_array(arr=state.get_vector(), numbering=self.numbering)
+        wfn = QubitWaveFunction.from_array(array=state.get_vector(), numbering=self.numbering)
         return wfn
 
     def convert_measurements(self, backend_result, target_qubits=None) -> QubitWaveFunction:
@@ -170,22 +169,17 @@ def convert_measurements(self, backend_result, target_qubits=None) -> QubitWaveF
             results transformed to tequila native QubitWaveFunction
         """
 
-        result = QubitWaveFunction()
+        result = QubitWaveFunction(self.n_qubits, self.numbering)
         # todo there are faster ways
 
-
         for k in backend_result:
-            converted_key = BitString.from_binary(BitStringLSB.from_int(integer=k, nbits=self.n_qubits).binary)
-            if converted_key in result._state:
-                result._state[converted_key] += 1
-            else:
-                result._state[converted_key] = 1
+            result[k] += 1
 
         if target_qubits is not None:
             mapped_target = [self.qubit_map[q].number for q in target_qubits]
             mapped_full = [self.qubit_map[q].number for q in self.abstract_qubits]
             keymap = KeyMapRegisterToSubregister(subregister=mapped_target, register=mapped_full)
-            result = result.apply_keymap(keymap=keymap)
+            result = QubitWaveFunction.from_wavefunction(result, keymap, n_qubits=len(target_qubits))
 
         return result
 
@@ -212,8 +206,7 @@ def do_sample(self, samples, circuit, noise_model=None, initial_state=0, *args,
             the results of sampling, as a Qubit Wave Function.
         """
         state = self.initialize_state(self.n_qubits)
-        lsb = BitStringLSB.from_int(initial_state, nbits=self.n_qubits)
-        state.set_computational_basis(BitString.from_binary(lsb.binary).integer)
+        state.set_computational_basis(reverse_int_bits(initial_state, self.n_qubits))
         circuit.update_quantum_state(state)
         sampled = state.sampling(samples)
         return self.convert_measurements(backend_result=sampled, target_qubits=self.measurements)