# KeyError: tensor(0, requires\_grad=True)

**URL:** <https://discuss.pennylane.ai/t/keyerror-tensor-0-requires-grad-true/2554>\
**Category:** PennyLane Help\
**Created:** [February 14, 2023, 10:45pm UTC](https://discuss.pennylane.ai/t/keyerror-tensor-0-requires-grad-true/2554 "2023-02-14T22:45:44Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![RX1](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/rx1/32/698_2.png) [@RX1](https://discuss.pennylane.ai/u/RX1)\
**Post date:** [February 14, 2023, 10:45pm UTC](https://discuss.pennylane.ai/t/keyerror-tensor-0-requires-grad-true/2554/1 "2023-02-14T22:45:44Z")

</div>

I’m having the following problem when running my code, it’s an error that occurs when drawing a quantum circuit diagram.

```auto
KeyError Traceback (most recent call last)
Input In [7], in <cell line: 50>()
     43 return qml.expval(qml.PauliZ(2 * wire))
     49 qml.drawer.use_style('black_white')
---> 50 fig, ax = qml.draw_mpl(Circ, show_all_wires=True)(X[0], X[1], params_init)
     51 fig.set_size_inches((10, 5))

File d:\miniconda3\lib\site-packages\pennylane\drawer\draw.py:446, in draw_mpl.<locals>.wrapper(*args, **kwargs_qnode)
    442 qnode.expansion_strategy = original_expansion_strategy
    444 _wire_order = wire_order or qnode.device.wires
--> 446 return tape_mpl(
    447 qnode.qtape,
    448 wire_order=_wire_order,
    449 show_all_wires=show_all_wires,
    450 decimals=decimals,
    451 style=style,
    452 **kwargs,
    453 )

File d:\miniconda3\lib\site-packages\pennylane\drawer\tape_mpl.py:353, in tape_mpl(tape, wire_order, show_all_wires, decimals, style, **kwargs)
    351 use_style(style)
    352 try:
--> 353 return _tape_mpl(
    354 tape, wire_order=wire_order, show_all_wires=show_all_wires, decimals=decimals, **kwargs
    355 )
    356 finally:
    357 if style and has_mpl:
    358 # we don't want to mess with how it modifies whether the interface is interactive
    359 # but we want to restore everything else

File d:\miniconda3\lib\site-packages\pennylane\drawer\tape_mpl.py:106, in _tape_mpl(tape, wire_order, show_all_wires, decimals, **kwargs)
    102 fontsize = kwargs.get("fontsize", None)
    104 wire_map = convert_wire_order(tape, wire_order=wire_order, show_all_wires=show_all_wires)
--> 106 layers = drawable_layers(tape.operations, wire_map=wire_map)
    108 n_layers = len(layers)
    109 n_wires = len(wire_map)

File d:\miniconda3\lib\site-packages\pennylane\drawer\drawable_layers.py:101, in drawable_layers(ops, wire_map)
     99 op_occupied_wires = mapped_wires
    100 else:
--> 101 mapped_wires = {wire_map[wire] for wire in op.wires}
    102 # get all integers from the minimum to the maximum
    103 min_wire = min(mapped_wires)

File d:\miniconda3\lib\site-packages\pennylane\drawer\drawable_layers.py:101, in <setcomp>(.0)
     99 op_occupied_wires = mapped_wires
    100 else:
--> 101 mapped_wires = {wire_map[wire] for wire in op.wires}
    102 # get all integers from the minimum to the maximum
    103 min_wire = min(mapped_wires)

KeyError: tensor(0, requires_grad=True)

```

@isaacdevlugt  
@Maria_Schuld  
@CatalinaAlbornoz

---

<div class="post-metadata">

**Author:** ![Alvaro\_Ballon](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/alvaro_ballon/32/874_2.png) [@Alvaro\_Ballon](https://discuss.pennylane.ai/u/Alvaro_Ballon)\
**Post date:** [February 15, 2023, 6:17pm UTC](https://discuss.pennylane.ai/t/keyerror-tensor-0-requires-grad-true/2554/2 "2023-02-15T18:17:30Z")

</div>

Hello!

We could use more information in order to reproduce the error and see what’s going on. Could you send us the code of the circuit that you’d like to plot?

Cheers,

Alvaro

---

<div class="post-metadata">

**Author:** ![RX1](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/rx1/32/698_2.png) [@RX1](https://discuss.pennylane.ai/u/RX1)\
**Post date:** [February 15, 2023, 9:57pm UTC](https://discuss.pennylane.ai/t/keyerror-tensor-0-requires-grad-true/2554/3 "2023-02-15T21:57:48Z")

</div>

Sorry, there is no intention to publicize the code yet, but it would be great to be able to point out the problem in private.

---

<div class="post-metadata">

**Author:** ![RX1](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/rx1/32/698_2.png) [@RX1](https://discuss.pennylane.ai/u/RX1)\
**Post date:** [February 15, 2023, 10:49pm UTC](https://discuss.pennylane.ai/t/keyerror-tensor-0-requires-grad-true/2554/4 "2023-02-15T22:49:42Z")

</div>

```auto
Using AmplitudeEmbedding`:
>print(Circ(X[0], X[1], params_init))

KeyError Traceback (most recent call last)
File d:\miniconda3\lib\site-packages\pennylane\devices\default_qubit.py:219, in DefaultQubit.map_wires(self, wires)
    218 try:
--> 219 mapped_wires = [self.wire_map[w] for w in wires]
    220 except KeyError as e:

File d:\miniconda3\lib\site-packages\pennylane\devices\default_qubit.py:219, in <listcomp>(.0)
    218 try:
--> 219 mapped_wires = [self.wire_map[w] for w in wires]
    220 except KeyError as e:

KeyError: tensor(0, requires_grad=True)

The above exception was the direct cause of the following exception:

WireError Traceback (most recent call last)
Input In [21], in <cell line: 46>()
     43 Ansatz(params[(3 * wire): (4 * wire)], wire, (2 * wire))
     44 return qml.expval(qml.PauliZ(3))
---> 46 print(Circ(X[0], X[1], params_init))
     48 '''
     49 qml.drawer.use_style('black_white')
     50 fig, ax = qml.draw_mpl(Circ, show_all_wires=True)(X[0], X[1], params_init)
     51 fig.set_size_inches((10, 5))
     52 '''

File d:\miniconda3\lib\site-packages\pennylane\qnode.py:847, in QNode. __call__ (self, *args, **kwargs)
    843 self._update_original_device()
    845 return res
--> 847 res = qml.execute(
    848 [self.tape],
    849 device=self.device,
    850 gradient_fn=self.gradient_fn,
    851 interface=self.interface,
    852 gradient_kwargs=self.gradient_kwargs,
    853 override_shots=override_shots,
    854 **self.execute_kwargs,
    855 )
    857 if old_interface == "auto":
    858 self.interface = "auto"

File d:\miniconda3\lib\site-packages\pennylane\interfaces\execution.py:651, in execute(tapes, device, gradient_fn, interface, mode, gradient_kwargs, cache, cachesize, max_diff, override_shots, expand_fn, max_expansion, device_batch_transform)
    647 return batch_fn(res)
    649 if gradient_fn == "backprop" or interface is None:
    650 return batch_fn(
--> 651 qml.interfaces.cache_execute(
    652 batch_execute, cache, return_tuple=False, expand_fn=expand_fn
    653 )(tapes)
    654 )
    656 # the default execution function is batch_execute
    657 execute_fn = qml.interfaces.cache_execute(batch_execute, cache, expand_fn=expand_fn)

File d:\miniconda3\lib\site-packages\pennylane\interfaces\execution.py:206, in cache_execute.<locals>.wrapper(tapes, **kwargs)
    202 return (res, []) if return_tuple else res
    204 else:
    205 # execute all unique tapes that do not exist in the cache
--> 206 res = fn(execution_tapes.values(), **kwargs)
    208 final_res = []
    210 for i, tape in enumerate(tapes):

File d:\miniconda3\lib\site-packages\pennylane\interfaces\execution.py:131, in cache_execute.<locals>.fn(tapes, **kwargs)
    129 def fn(tapes: Sequence[QuantumTape], **kwargs): # pylint: disable=function-redefined
    130 tapes = [expand_fn(tape) for tape in tapes]
--> 131 return original_fn(tapes, **kwargs)

File d:\miniconda3\lib\contextlib.py:79, in ContextDecorator. __call__.<locals>.inner(*args, **kwds)
     76 @wraps(func)
     77 def inner(*args, **kwds):
     78 with self._recreate_cm():
---> 79 return func(*args, **kwds)

File d:\miniconda3\lib\site-packages\pennylane\_qubit_device.py:656, in QubitDevice.batch_execute(self, circuits)
    653 self.reset()
    655 # TODO: Insert control on value here
--> 656 res = self.execute(circuit)
    657 results.append(res)
    659 if self.tracker.active:

File d:\miniconda3\lib\site-packages\pennylane\_qubit_device.py:432, in QubitDevice.execute(self, circuit, **kwargs)
    429 self.check_validity(circuit.operations, circuit.observables)
    431 # apply all circuit operations
--> 432 self.apply(circuit.operations, rotations=circuit.diagonalizing_gates, **kwargs)
    434 # generate computational basis samples
    435 if self.shots is not None or circuit.is_sampled:

File d:\miniconda3\lib\site-packages\pennylane\devices\default_qubit.py:258, in DefaultQubit.apply(self, operations, rotations, **kwargs)
    252 raise DeviceError(
    253 f"Operation {operation.name} cannot be used after other Operations have already been applied "
    254 f"on a {self.short_name} device."
    255 )
    257 if isinstance(operation, QubitStateVector):
--> 258 self._apply_state_vector(operation.parameters[0], operation.wires)
    259 elif isinstance(operation, BasisState):
    260 self._apply_basis_state(operation.parameters[0], operation.wires)

File d:\miniconda3\lib\site-packages\pennylane\devices\default_qubit.py:687, in DefaultQubit._apply_state_vector(self, state, device_wires)
    678 """Initialize the internal state vector in a specified state.
    679 
    680 Args:
   (...)
    683 device_wires (Wires): wires that get initialized in the state
    684 """
    686 # translate to wire labels used by device
--> 687 device_wires = self.map_wires(device_wires)
    688 dim = 2 ** len(device_wires)
    690 state = self._asarray(state, dtype=self.C_DTYPE)

File d:\miniconda3\lib\site-packages\pennylane\devices\default_qubit.py:221, in DefaultQubit.map_wires(self, wires)
    219 mapped_wires = [self.wire_map[w] for w in wires]
    220 except KeyError as e:
--> 221 raise WireError(
    222 f"Did not find some of the wires {wires.labels} on device with wires {self.wires.labels}."
    223 ) from e
    225 return mapped_wires

WireError: Did not find some of the wires (tensor(0, requires_grad=True), tensor(1, requires_grad=True), tensor(2, requires_grad=True)) on device with wires (0, 1, 2, 3, 4, 5).

```

```auto
Using MottonenStatePreparation:
>print(Circ(X[0], X[1], params_init))

---------------------------------------------------------------------------
KeyError Traceback (most recent call last)
File d:\miniconda3\lib\site-packages\pennylane\devices\default_qubit.py:219, in DefaultQubit.map_wires(self, wires)
    218 try:
--> 219 mapped_wires = [self.wire_map[w] for w in wires]
    220 except KeyError as e:

File d:\miniconda3\lib\site-packages\pennylane\devices\default_qubit.py:219, in <listcomp>(.0)
    218 try:
--> 219 mapped_wires = [self.wire_map[w] for w in wires]
    220 except KeyError as e:

KeyError: tensor(0, requires_grad=True)

The above exception was the direct cause of the following exception:

WireError Traceback (most recent call last)
Input In [38], in <cell line: 48>()
     44 Ansatz(params[(3 * wire): (4 * wire)], wire, (2 * wire))
     45 return qml.expval(qml.PauliZ(3))
---> 48 print(Circ(X[0], X[1], params_init))
     50 '''
     51 qml.drawer.use_style('black_white')
     52 fig, ax = qml.draw_mpl(Circ, show_all_wires=True)(X[0], X[1], params_init)
     53 fig.set_size_inches((10, 5))
     54 '''

File d:\miniconda3\lib\site-packages\pennylane\qnode.py:847, in QNode. __call__ (self, *args, **kwargs)
    843 self._update_original_device()
    845 return res
--> 847 res = qml.execute(
    848 [self.tape],
    849 device=self.device,
    850 gradient_fn=self.gradient_fn,
    851 interface=self.interface,
    852 gradient_kwargs=self.gradient_kwargs,
    853 override_shots=override_shots,
    854 **self.execute_kwargs,
    855 )
    857 if old_interface == "auto":
    858 self.interface = "auto"

File d:\miniconda3\lib\site-packages\pennylane\interfaces\execution.py:651, in execute(tapes, device, gradient_fn, interface, mode, gradient_kwargs, cache, cachesize, max_diff, override_shots, expand_fn, max_expansion, device_batch_transform)
    647 return batch_fn(res)
    649 if gradient_fn == "backprop" or interface is None:
    650 return batch_fn(
--> 651 qml.interfaces.cache_execute(
    652 batch_execute, cache, return_tuple=False, expand_fn=expand_fn
    653 )(tapes)
    654 )
    656 # the default execution function is batch_execute
    657 execute_fn = qml.interfaces.cache_execute(batch_execute, cache, expand_fn=expand_fn)

File d:\miniconda3\lib\site-packages\pennylane\interfaces\execution.py:206, in cache_execute.<locals>.wrapper(tapes, **kwargs)
    202 return (res, []) if return_tuple else res
    204 else:
    205 # execute all unique tapes that do not exist in the cache
--> 206 res = fn(execution_tapes.values(), **kwargs)
    208 final_res = []
    210 for i, tape in enumerate(tapes):

File d:\miniconda3\lib\site-packages\pennylane\interfaces\execution.py:131, in cache_execute.<locals>.fn(tapes, **kwargs)
    129 def fn(tapes: Sequence[QuantumTape], **kwargs): # pylint: disable=function-redefined
    130 tapes = [expand_fn(tape) for tape in tapes]
--> 131 return original_fn(tapes, **kwargs)

File d:\miniconda3\lib\contextlib.py:79, in ContextDecorator. __call__.<locals>.inner(*args, **kwds)
     76 @wraps(func)
     77 def inner(*args, **kwds):
     78 with self._recreate_cm():
---> 79 return func(*args, **kwds)

File d:\miniconda3\lib\site-packages\pennylane\_qubit_device.py:656, in QubitDevice.batch_execute(self, circuits)
    653 self.reset()
    655 # TODO: Insert control on value here
--> 656 res = self.execute(circuit)
    657 results.append(res)
    659 if self.tracker.active:

File d:\miniconda3\lib\site-packages\pennylane\_qubit_device.py:432, in QubitDevice.execute(self, circuit, **kwargs)
    429 self.check_validity(circuit.operations, circuit.observables)
    431 # apply all circuit operations
--> 432 self.apply(circuit.operations, rotations=circuit.diagonalizing_gates, **kwargs)
    434 # generate computational basis samples
    435 if self.shots is not None or circuit.is_sampled:

File d:\miniconda3\lib\site-packages\pennylane\devices\default_qubit.py:269, in DefaultQubit.apply(self, operations, rotations, **kwargs)
    267 self._debugger.snapshots[len(self._debugger.snapshots)] = state_vector
    268 else:
--> 269 self._state = self._apply_operation(self._state, operation)
    271 # store the pre-rotated state
    272 self._pre_rotated_state = self._state

File d:\miniconda3\lib\site-packages\pennylane\devices\default_qubit.py:303, in DefaultQubit._apply_operation(self, state, operation)
    300 return self._apply_diagonal_unitary(state, matrix, wires)
    301 if len(wires) <= 2:
    302 # Einsum is faster for small gates
--> 303 return self._apply_unitary_einsum(state, matrix, wires)
    305 return self._apply_unitary(state, matrix, wires)

File d:\miniconda3\lib\site-packages\pennylane\devices\default_qubit.py:829, in DefaultQubit._apply_unitary_einsum(self, state, mat, wires)
    815 r"""Apply multiplication of a matrix to subsystems of the quantum state.
    816 
    817 This function uses einsum instead of tensordot. This approach is only
   (...)
    826 array[complex]: output state
    827 """
    828 # translate to wire labels used by device
--> 829 device_wires = self.map_wires(wires)
    831 dim = 2 ** len(device_wires)
    832 batch_size = self._get_batch_size(mat, (dim, dim), dim**2)

File d:\miniconda3\lib\site-packages\pennylane\devices\default_qubit.py:221, in DefaultQubit.map_wires(self, wires)
    219 mapped_wires = [self.wire_map[w] for w in wires]
    220 except KeyError as e:
--> 221 raise WireError(
    222 f"Did not find some of the wires {wires.labels} on device with wires {self.wires.labels}."
    223 ) from e
    225 return mapped_wires

WireError: Did not find some of the wires (tensor(0, requires_grad=True),) on device with wires (0, 1, 2, 3, 4, 5).
```

---

<div class="post-metadata">

**Author:** ![RX1](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/rx1/32/698_2.png) [@RX1](https://discuss.pennylane.ai/u/RX1)\
**Post date:** [February 15, 2023, 11:17pm UTC](https://discuss.pennylane.ai/t/keyerror-tensor-0-requires-grad-true/2554/5 "2023-02-15T23:17:52Z")

</div>

I found that the problem comes from the AmplitudeEmbedding function and the MottonenStatePreparation function, when using the AmplitudeEmbedding function there is a problem with multiple wires not being found, while using the MottonenStatePreparation function makes fewer wires not being found, but the problem still exists

---

<div class="post-metadata">

**Author:** ![RX1](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/rx1/32/698_2.png) [@RX1](https://discuss.pennylane.ai/u/RX1)\
**Post date:** [February 16, 2023, 2:59pm UTC](https://discuss.pennylane.ai/t/keyerror-tensor-0-requires-grad-true/2554/6 "2023-02-16T14:59:48Z")

</div>

wires = np.arange(wires\_start, wires\_end).tolist()

---

<div class="post-metadata">

**Author:** ![CatalinaAlbornoz](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/catalinaalbornoz/32/1196_2.png) [@CatalinaAlbornoz](https://discuss.pennylane.ai/u/CatalinaAlbornoz)\
**Post date:** [February 17, 2023, 10:34pm UTC](https://discuss.pennylane.ai/t/keyerror-tensor-0-requires-grad-true/2554/7 "2023-02-17T22:34:59Z")

</div>

Thank you for posting the solution here @RX1 !