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18 votes

Why do the IBM and Google processors both have 53 qubits?

It's just a coincidence. I can speak from personal recollection on the Google side. Google originally intended to use a 72 qubit chip (Bristlecone) where qubits were essentially directly connected to ...
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10 votes

Topology graphs of IBM's quantum computers

The graph shows you how the physical qubits are connected together on the real device you will be using. For example, on the graph you put, qubit 0 has a physical connection to qubit 1 and qubit 14 on ...
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9 votes

Why IBM devices have the same number of qubit and the same architecture, but the error rates are different?

They have different error rates because they are two different physical devices! This relates to the manufacturing processes of these chips. Every device is unique and will have its own fingerprint ...
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9 votes

Would IBM's "compiler" turn my identity circuit into nothing?

Any compilation/circuit optimization happens transparently by Qiskit. As a user you have control over what happens via the optimization_level argument passed to <...
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  • 1,542
9 votes
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Characteristics of the IBM quantum computer

A quick and dirty list: $T_{1}$ and $T_{2}$ - colloquially known as decoherence times, but slightly more precisely also as the (qubit) relaxation time ($T_{1}$) and the (qubit) dephasing time ($T_{2}...
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  • 4,659
8 votes
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How to explain in layman’s terms the significance of the difference of qubits of the D-Wave and IBM QX?

In the classical case, there is a pretty big difference between digital computers and analogue ones. The methodology and hardware is very much distinct (in all cases I know of, at least). The divide ...
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7 votes

How to create the state $\vert 0 \rangle+i \vert 1 \rangle$ using elementary gates?

Starting with the state $|\psi_0 \rangle = |0\rangle$, and we want to get to the state $|\psi_f \rangle = \dfrac{|0\rangle + i|1\rangle}{\sqrt{2}}$ then we must realize that we need to create some ...
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  • 12.3k
6 votes

What is maximum circuit depth and size IBM Q5 and Q16 could handle?

From the public data given by IBM about IBM Q16 Melbourne (14 qubits available): Mean gate error: $2.14 \times 10^{-3}$ (probably higher for CX and lower for 1-...
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  • 4,467
6 votes

What is maximum circuit depth and size IBM Q5 and Q16 could handle?

It depends on what you mean by "able to handle". You mention a circuit depth of 99, which might be possible, but what will be the fidelity of the final state with respect to the one it's supposed to ...
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  • 151
6 votes

What are the differences between the IBM machines?

Besides number of qubits, the devices can have other differences as well. The architecture of the device can be different, meaning that each device could have different connectivity maps. This would ...
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6 votes

How are the IBM's and Google's Hadamard gates fabricated and operated?

A Hadamard gate isn't usually a physical object that you pass qubits through. In the case of superconducting qubits, the Hadamard gate is performed by bouncing microwaves off of the qubits. It doesn't ...
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  • 21.9k
6 votes

Topology graphs of IBM's quantum computers

To add onto Lena answer. The plot topology graph of the device represents the qubit layout of the hardware. The qubits on IBM hardware are fixed. They don't move around as trapped-ion qubits built by ...
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  • 12.3k
6 votes
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Can I access device specifications of IBMQ paying devices?

The first thing that comes to my mind with your problem is the fake devices available in Qiskit. Here is how to use it, the main idea is that Qiskit stored device properties in Terra and with it, you ...
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  • 2,334
6 votes

Characteristics of the IBM quantum computer

Just adding some stuff to the already good answer : The gate time actually is related to the connexion between qubits, so is related to the CNOT, not the single-qubit gates. The frequency is defined ...
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  • 2,334
5 votes

Why qiskit superconducting device native gates different from that of trapped ion device?

The choice of gates is entirely dependent on the types of interactions that occur in the different architectures. The cross resonance gate used by IBM generates the ZX interaction you want (plus other ...
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  • 2,149
5 votes
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What extra functionality is available to an IBM Q Network member over a regular IBM Q Experience user

Basically being IBM Q Network member give you the possibility to access IBM’s most-powerful quantum computing systems through the cloud (currently 20Q, 27Q, 28Q, 53Q devices with Quantum Volume ...
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  • 116
5 votes
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Qiskit: Initializing $n$ qubits with binary values ($0$s and $1$s)

You can also create a Statevector, that can be directly initialized as follows: ...
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  • 192
5 votes

Qiskit: Initializing $n$ qubits with binary values ($0$s and $1$s)

qiskit-terra 0.16 or lower As answered, probably the most canonical way to do this is with Statevector.from_label and initialize....
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  • 3,771
5 votes

What are the differences between the IBM machines?

First of all, the name of backends (devices) have nothing to do with their location! They are all located in US. Back to your question, as others already mentioned the difference is in the ...
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  • 438
5 votes
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Is there any way to obtain the number of qubits of a given backend in Qiskit?

The number of qubits is part of the backend configuration: FakeManhattan().configuration().n_qubits 65 If you need to filter ...
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  • 3,771
5 votes
Accepted

What use cases are there for 127 qubit QPUs?

I think that the main reason behind is to tackle technical difficulties connected with building huge number of qubits. Having hundred of qubits brings about issues with interconnection, connections to ...
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4 votes

Current limits on Grover search space

I am going to try to give guesses that can make sense: More qubits does not mean better machines. They may be less noise-tolerant and with less connectivity between qubits. That is why, when you ...
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  • 4,554
4 votes

D-Wave systems and IBM Q System One

When referring to the commercial quantum computers of both parties, it is that both are based on a different quantum principles. The D-Wave machine works via quantum annealing and is suited for ...
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  • 1,402
4 votes

'IBMQFactory' object has no attribute 'load_accounts'

IBMQ.load_accounts() was deprecated and removed in Qiskit 0.14. Please use IBMQ.load_account().
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  • 2,149
4 votes

How are the IBM's and Google's Hadamard gates fabricated and operated?

Fundamentally, a device such as an IBM quantum computer interacts according to a Hamiltonian, which might have some time-varying parameters. For example, for a single qubit, it might look like: $$ H=...
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  • 46.3k
4 votes
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Is every computer in IBM's fleet based on superconductivity?

Yes. IBM uses superconducting Transmon qubit. Here is a quote from IBM's website: At the heart of IBM quantum systems is the transmon qubit. Successive generations of IBM Quantum processors have ...
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  • 12.3k
4 votes

Qiskit's c_if and conditioned operations on a real quantum computer

As far as I know, c_if operation is not implementable on IBM's hardware currently. But it should be implementable on simulator. For instance, if I tried to execute ...
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  • 12.3k
4 votes

Error 400 on submission request on job that ran before

This was due to temporary issue on IBM side. If you try to resubmit your job it should work as before.
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  • 116
4 votes
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Why is a 15-qubit IBM quantum computer not working correctly?

There will be a lot of swapping and additional gates during the execution of your circuit since CCX is not a native gate. The actual circuit that is being executed is something like: This circuit has ...
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  • 12.3k
4 votes
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CNOT error rate of 1 in IBM backends

Great observation! The devices are calibrated daily(ish) and sometimes a bad calibration requires a "rerun". The value 1 is some sort of flag that something went wrong with the calibration. ...
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