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Circuit incorrectly justifed

See original GitHub issue

Information

Qiskit Terra version: master
Python version: 3.7
Operating system: macOS

What is the current behavior?

The following circuit is not correctly justified, the first U2 after the measure appears in its own column, rather than underneath the other U2.

Steps to reproduce the problem

qasm = """
OPENQASM 2.0;
include "qelib1.inc";
qreg q[5];
creg c1[1];
u2(0,3.14159265358979) q[0];
u2(0,3.14159265358979) q[1];
cx q[1],q[0];
u2(0,3.14159265358979) q[0];
u2(0,3.14159265358979) q[1];
u2(0,3.14159265358979) q[1];
measure q[0] -> c1[0];
u2(0,3.14159265358979) q[0];
cx q[1],q[0];
u2(0,3.14159265358979) q[0];
u2(0,3.14159265358979) q[1];
 """
from qiskit import QuantumCircuit
qc = QuantumCircuit.from_qasm_str(qasm)
print(qc)

        ┌──────────────┐┌───┐┌──────────────┐┌─┐                ┌──────────────┐┌───┐┌──────────────┐
q_0: |0>┤ U2(0,3.1416) ├┤ X ├┤ U2(0,3.1416) ├┤M├────────────────┤ U2(0,3.1416) ├┤ X ├┤ U2(0,3.1416) ├
        ├──────────────┤└─┬─┘├──────────────┤└╥┘┌──────────────┐└──────────────┘└─┬─┘├──────────────┤
q_1: |0>┤ U2(0,3.1416) ├──■──┤ U2(0,3.1416) ├─╫─┤ U2(0,3.1416) ├──────────────────■──┤ U2(0,3.1416) ├
        └──────────────┘     └──────────────┘ ║ └──────────────┘                     └──────────────┘
q_2: |0>──────────────────────────────────────╫──────────────────────────────────────────────────────
                                              ║                                                      
q_3: |0>──────────────────────────────────────╫──────────────────────────────────────────────────────
                                              ║                                                      
q_4: |0>──────────────────────────────────────╫──────────────────────────────────────────────────────
                                              ║                                                      
c1_0: 0 ══════════════════════════════════════╩══════════════════════════════════════════════════════

What is the expected behavior?

        ┌──────────────┐┌───┐┌──────────────┐┌─┐┌──────────────┐┌───┐┌──────────────┐
q_0: |0>┤ U2(0,3.1416) ├┤ X ├┤ U2(0,3.1416) ├┤M├┤ U2(0,3.1416) ├┤ X ├┤ U2(0,3.1416) ├
        ├──────────────┤└─┬─┘├──────────────┤└╥┘├──────────────┤└─┬─┘├──────────────┤
q_1: |0>┤ U2(0,3.1416) ├──■──┤ U2(0,3.1416) ├─╫─┤ U2(0,3.1416) ├──■──┤ U2(0,3.1416) ├
        └──────────────┘     └──────────────┘ ║ └──────────────┘     └──────────────┘
q_2: |0>──────────────────────────────────────╫──────────────────────────────────────
                                              ║                                                      
q_3: |0>──────────────────────────────────────╫──────────────────────────────────────
                                              ║                                                      
q_4: |0>──────────────────────────────────────╫──────────────────────────────────────
                                              ║                                                      
c1_0: 0 ══════════════════════════════════════╩══════════════════════════════════════

Issue Analytics

State:
Created 4 years ago
Comments:27 (27 by maintainers)

Top GitHub Comments

2reactions

jwoehrcommented, Aug 12, 2019

It seems like this example has the same issue (last round of H):

@1ucian0 , I recreate qasm for the circuit you illustrated above and test draw left, right, and none with this code:

qasm = """
OPENQASM 2.0;
include "qelib1.inc";
qreg q[4];
h q[0];
h q[1];
h q[2];
h q[3];
cx q[0],q[3];
h q[1];
cx q[0],q[2];
cx q[0],q[1];
h q[2];
cx q[0],q[1];
h q[2];
cx q[0],q[2];
h q[1];
cx q[0],q[3];
h q[0];
h q[1];
h q[2];
h q[3];
 """
from qiskit import QuantumCircuit
qc = QuantumCircuit.from_qasm_str(qasm)
print("draw left")
print(qc.draw(justify='left'))
print("draw right")
print(qc.draw(justify='right'))
print("draw none")
print(qc.draw(justify='none'))

The resulting output is show below. Am I correct that both left and right are incorrect (left for the reason you pointed out above, and right for the positioning of the last h q[3]) while none is correct?

draw left
        ┌───┐                                             ┌───┐
q_0: |0>┤ H ├──■─────────■────■────■────■─────────■───────┤ H ├
        ├───┤  │  ┌───┐  │  ┌─┴─┐┌─┴─┐  │  ┌───┐  │  ┌───┐└───┘
q_1: |0>┤ H ├──┼──┤ H ├──┼──┤ X ├┤ X ├──┼──┤ H ├──┼──┤ H ├─────
        ├───┤  │  └───┘┌─┴─┐├───┤├───┤┌─┴─┐└───┘  │  ├───┤     
q_2: |0>┤ H ├──┼───────┤ X ├┤ H ├┤ H ├┤ X ├───────┼──┤ H ├─────
        ├───┤┌─┴─┐     └───┘└───┘└───┘└───┘     ┌─┴─┐└───┘┌───┐
q_3: |0>┤ H ├┤ X ├──────────────────────────────┤ X ├─────┤ H ├
        └───┘└───┘                              └───┘     └───┘
draw right
        ┌───┐                                        ┌───┐
q_0: |0>┤ H ├──■─────────■────■────■────■─────────■──┤ H ├
        ├───┤  │  ┌───┐  │  ┌─┴─┐┌─┴─┐  │  ┌───┐  │  ├───┤
q_1: |0>┤ H ├──┼──┤ H ├──┼──┤ X ├┤ X ├──┼──┤ H ├──┼──┤ H ├
        ├───┤  │  └───┘┌─┴─┐├───┤├───┤┌─┴─┐├───┤  │  └───┘
q_2: |0>┤ H ├──┼───────┤ X ├┤ H ├┤ H ├┤ X ├┤ H ├──┼───────
        ├───┤┌─┴─┐     └───┘└───┘└───┘└───┘└───┘┌─┴─┐┌───┐
q_3: |0>┤ H ├┤ X ├──────────────────────────────┤ X ├┤ H ├
        └───┘└───┘                              └───┘└───┘
draw none
        ┌───┐                                                                      ┌───┐          
q_0: |0>┤ H ├──────────────────────■────■────■────■────────────────────────■────■──┤ H ├──────────
        └───┘┌───┐┌───┐            │    │  ┌─┴─┐┌─┴─┐┌───┐┌───┐            │    │  └───┘          
q_1: |0>─────┤ H ├┤ H ├────────────┼────┼──┤ X ├┤ X ├┤ H ├┤ H ├────────────┼────┼─────────────────
             └───┘└───┘┌───┐       │  ┌─┴─┐└───┘└───┘└───┘└───┘┌───┐┌───┐┌─┴─┐  │       ┌───┐     
q_2: |0>───────────────┤ H ├───────┼──┤ X ├────────────────────┤ H ├┤ H ├┤ X ├──┼───────┤ H ├─────
                       └───┘┌───┐┌─┴─┐└───┘                    └───┘└───┘└───┘┌─┴─┐     └───┘┌───┐
q_3: |0>────────────────────┤ H ├┤ X ├────────────────────────────────────────┤ X ├──────────┤ H ├

2reactions

maddy-todcommented, Jul 17, 2019

I think the error is likely to be in qiskit-terra/qiskit/visualization/utils.py in the method _get_layered_instructions() as I am seeing the bug in both the mpl and the latex outputs too. It is probably an error with the way the layers are being generated rather than drawn.

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