21
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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 ...
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10
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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 ...
- 2,552
10
votes
Accepted
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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9
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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 ...
- 566
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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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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8
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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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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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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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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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7
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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.
...
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7
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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 ...
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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 ...
- 151
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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....
- 5,573
6
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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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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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6
votes
Accepted
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 ...
- 2,552
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 $...
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6
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Accepted
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 ...
- 5,573
6
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 ...
- 13.6k
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 ...
- 2,239
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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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votes
Accepted
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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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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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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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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5
votes
Accepted
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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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 ...
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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 ...
- 33.3k
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 ...
- 4,644
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