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I am a noob at quantum computing but I am certain the circuit is correct. I've tried increasing the number of shots, changing the quantum computer. I think it might be a problem with my ccccx gate? I am not sure I implemented it correctly. I've also been hearing something about connectivity, but my internet connection shouldn't be an issue?

I live in Australia and I've been using mainly IBM Quito. That computer has a shockingly of low queue 100 compared to the 10k queueing for the one in my city Melbourne, is there a known problem with IBM Quito?

For context my 2 qubit, 3 qubit circuit works perfectly. 2 qubit circuit works flawlessly 100% of the time finding the hidden variable. 3 qubit circuit has some hiccups but it still works maybe 70% of the time. 4 qubit one works maybe 10% of the time.

My 4Q Grover circuit

This was the only time after 20 attempts it got the result right

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    $\begingroup$ Sadly, the names of the machines is not where they are based. Also the connectivity generally refers to how the qubits are connected to eachother, rather than your internet connection. $\endgroup$
    – met927
    Apr 23 at 13:05
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Here is the qubit layout and error map for `ibmq_quito':

enter image description here

And when you try to execute your original circuit on 'ibmq_quito', what you are executing is something like the circuit below given ibmq_quito's qubits connectivity* and its native gate set ${CX, ID, RZ, SX, X}$ . This circuit has 196 gates altogether with about 50 CNOT gates.

enter image description here

You can use the error rate from the top figure and sort of workout the probability of failure in your circuit. You will see that you will have a pretty high chance of failure. Also note the Readout Error is pretty significant on qubit 0 and 1.


To get the the transpiled circuit and the error map, you can do the following:

from qiskit.compiler import transpile
provider = IBMQ.load_account()
backend = provider.get_backend('ibmq_quito')
Circuit_Transpile = transpile(circuit, backend , initial_layout =None, optimization_level=3)
Circuit_Transpile.draw( 'mpl',style={'name': 'bw'}, scale = 1)
from qiskit.visualization import plot_error_map
plot_error_map(backend)

You can also access the error rate through the Dash Board in IBM Quantum Experience. If you login to your IBM Quantum Experience, on the top left, you will see the following menu:

enter image description here

Click on that and you will see a list of devices. Click on any of those devices, you will be able to see its configuration.

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  • $\begingroup$ Wow! thanks for the help. how/where did you get the error map from? $\endgroup$
    – James Bian
    Apr 23 at 15:45
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    $\begingroup$ I added the code to the edit answer. $\endgroup$
    – KAJ226
    Apr 23 at 15:59
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    $\begingroup$ Thank you so much KAJ this was great help. Much appreciated! $\endgroup$
    – James Bian
    Apr 24 at 3:30

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