22 votes
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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 ...
Craig Gidney's user avatar
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11 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 ...
Lena's user avatar
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11 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}...
JSdJ's user avatar
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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 ...
Turbotanten's user avatar
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 <...
Ali Javadi's user avatar
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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 ...
James Wootton's user avatar
8 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-...
Adrien Suau's user avatar
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8 votes
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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 ...
Craig Gidney's user avatar
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7 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....
luciano's user avatar
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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 ...
KAJ226's user avatar
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7 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 ...
Lena's user avatar
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7 votes
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How the real IBM quantum computers apply arbitrary Rz(θ) gate rotation?

Answering question (1): Z rotations are implemented purely in software by changing the relative phase between the projection of the qubit vector on the Bloch sphere and the microwave control tone. ...
Lior's user avatar
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7 votes

Sycamore 2 versus Osprey

One way you can compare Google's chips and IBM's chips is by computing detection fractions. Error correcting codes are built out of "detectors", which are sets of measurements with ...
Craig Gidney's user avatar
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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 ...
CARNEGIE's user avatar
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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 ...
Matthew Stypulkoski's user avatar
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 ...
KAJ226's user avatar
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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 ...
Lena's user avatar
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6 votes

Where is CZ gate in IBM Quantum circuit composer

There is no Controlled-Z in the circuit composer by default because this gate can be built from CNOT ($CX$) and Hadamard gate $H$. This is because we have the identity $$ Z = HXH$$ This implies that $...
KAJ226's user avatar
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6 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 ...
luciano's user avatar
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6 votes
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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 ...
Martin Vesely's user avatar
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 ...
Paul Nation's user avatar
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5 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 ...
nippon's user avatar
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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 ...
Francois's user avatar
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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: ...
e-eight's user avatar
  • 302
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 ...
26118in's user avatar
  • 488
5 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 ...
KAJ226's user avatar
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5 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. ...
luciano's user avatar
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5 votes

Reasonable Circuit Depth

Under current state of development (decoherence times in range of hundred microseconds), it is impossible to run circuits with depth in range of thousands gates. My experience is that even circuits ...
Martin Vesely's user avatar
5 votes

Reasonable Circuit Depth

Currently, a reasonable circuit depth is 10-100 layers. Getting good results above 100 layers requires substantial effort, unless you're using a tiny number of qubits. For scale, I think so far the ...
Craig Gidney's user avatar
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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 ...
cnada's user avatar
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