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I'm following the YouTube tutorials for Programming on Quantum Computers and I've completed everything until I reach circuit.draw() since I don't get $|0\rangle$ or 0 next to q or c. Here's my code:

from qiskit import *

qr = QuantumRegister(2)
cr = ClassicalRegister(2)
circuit = QuantumCircuit(qr, cr)

%matplotlib inline

circuit.draw()

[
q0_0:
q0_1:
c0: 2/
]

and so when I attempt an H gate, I receive the error 'QuantumRegister' object is not callable:

circuit.h(qr(0))

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-55-c8b4318b743b> in <module>
----> 1 circuit.h(qr(0))

TypeError: 'QuantumRegister' object is not callable
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2 Answers 2

Reset to default
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There is probably a change on the default arguments of draw() function. To reproduce the same visualization as on the youtube video, try:

circuit.draw(initial_state=True, 
             cregbundle=False)

and add a Hadamard gate like:

circuit.h(qr[0])
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2
  • $\begingroup$ Awesome! Thanks a lot. Where can I see other changes as to avoid problems like this in the future? $\endgroup$
    – Riad Dajani
    Oct 12, 2020 at 13:15
  • 2
    $\begingroup$ Qiskit Documentation is the place. For example, qiskit.org/documentation/stubs/… $\endgroup$
    – tsgeorgios
    Oct 12, 2020 at 13:19
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The following also work for me if it is interest to you:

from qiskit import *
%matplotlib inline

circuit = QuantumCircuit(2,2)
circuit.h(0)
circuit.draw()

enter image description here

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