All Questions
761 questions
2
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44
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Is there a standard approach to measure T2 time?
I saw that different ion trap quantum computer manufacturers have given their own T2 (dephasing) times, but it is not clear whether they are obtained by the same test steps.
My question is: Is there a ...
- 21
1
vote
0
answers
17
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How to get historical calibration data for mthree (M3) from IBM Quantum devices?
I'm using mthree in Batch mode. A batch needs to be queued before it can be executed. The time when a batch was executed can be obtained from the IBM Quantum Platform site, so I would like to obtain ...
- 11
0
votes
0
answers
88
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before_round_data_depolarization in Stim surface code circuits
I am working with Stim to do some circuit-level noise simulations and I have a doubt on the noise model and the stim implementation. I can generate stim circuits for the surface code using the ...
0
votes
0
answers
45
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RuntimeJobFailureError: 'Unable to retrieve job result. Error code 1520; The instruction cost per qubit exceeds the system limit
I want to find two operands of multiplication result of 180. In another word, finding integer factors of 180.
I'm using ...
2
votes
1
answer
72
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How quantum laws hold on macroscopic level in classical computers?
Disclaimer: I am not sure about whether my question is suitable for here, but I will ask it anyway.
I am making research about quantum cryptography, so I start reading a book. In one paragraph, it is ...
2
votes
0
answers
74
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Understanding sources of error in 4-bit Grover's search on IBM QC
This question is similar to some others I've come across, related to why a 4-qubit implementation of Grover's search yields such poor results when run on the IBM QC compared to the 3-qubit case (...
- 121
1
vote
1
answer
35
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Repetition code applied to decoherence-free subspaces
The repetition code (figure below) can be used to detect bit-flip errors. Such a code is useful for studying, but it can't be used in more general scenarios where also phase errors occur.
I was ...
- 2,058
0
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0
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18
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DEJMPS and EXPEDIENT distillation protocols implementation in qiskit
I am new to Qiskit and distillation protocols. I am wondering if there is a tutorial or a link to the implementation of the DEJMPS and EXPEDIENT distillation protocols in Qiskit.
What I want to ...
4
votes
1
answer
106
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Dephasing noise and error correction
It is my impression that $ Z $ errors are the dominant source of noise in many platforms used for quantum computing. For example, Ultrahigh Error Threshold for Surface Codes with Biased Noise says ...
- 4,936
0
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0
answers
18
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Does anyone have an idea about the execution power of IBM summit for VQE? I'd appreciate sources of papers as well for supercomputer execution
I'm trying to find the execution power of VQE in super computer and I want to know the factors of execution such as iterations, shots, convergence, etc. Please help me and also, I'd appreciate if ...
1
vote
1
answer
66
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Seeking Quantum Algorithm Implemented on IBM's Accessible Quantum Computers
I am interested in leveraging IBM's quantum computers that are currently available for public access. Specifically, I am looking for an algorithm that has been successfully implemented on a real, ...
- 51
0
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0
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42
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Run Qiskit Finance Tutorial on IBMQ backend
I tried to implement the qiskit example for portfolio optimization and it works as described. However I am not able to change the backend to one of the IBMQ machines - and it's not clear to me if this ...
4
votes
2
answers
151
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What are some good additional resources when taking IBM Qiskit course?
I am a undergrad comp sci major. I have committed myself to a neuroscience PhD, hopefully computational neuro. However, I recently came across quantum computing, and see that lots of resources are ...
- 61
1
vote
0
answers
74
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Performance of quantum annealing systems vs gate based ones
Quantum annealers like D-Wave can be used to solve Quadratic Unconstrained Binary Optimization (QUBO) which is a NP Hard problem (see here) while gate based quantum computers, like the ones created by ...
- 11
1
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0
answers
24
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Are reset gates allowed on IBM quantum computers?
My circuit involves many "reset" gates. After running on the IBM real backend, the experiment status says "Failed" with error message that says:
Failed - Unknown operation type ...
- 231
1
vote
1
answer
74
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What is the density matrix of a GHZ state when onle a qubit is in a decoherence channel?
Suppose Alice, Bob and Rob share a GHZ state. Now consider Rob's qubit is in a bit-flip channel. How to obtain the density matrix in this senario? Also i would be glad to get some articles adrresing ...
- 791
1
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0
answers
60
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qiskit transpile taking forever to run while CPU usage near zero
I am using the following code to use IBM's quantum computer. My understanding is that it is required before circuits are passed to the real quantum computers as certain operations and instructions ...
- 231
2
votes
1
answer
50
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Depolarizing channel on GHZ-state
Consider a GHZ-state $|\psi\rangle =\frac{1}{\sqrt{2}}(|0\rangle^{n}+|1\rangle^n)$, and consider a depolarizing channel that maps a density matrix
$$\rho\to(1-\lambda)\rho + \frac{\lambda}{2^d}I.$$
...
- 1,567
2
votes
2
answers
84
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IBMBackendValueError: number of circuits exceeds the maximum for this backend, 300
I am trying to run the QAOA on the IBMQ device. The QAOA circuit consists of 6 qubits, two layers. The number of total trainable parameters for the QAOA circuit is 14. The toy code is as follows:
<...
- 21
1
vote
0
answers
68
views
Low Fidelity In IBM Quantum Computers
I am just trying to calculate the highest fidelity of preparing GHZ states on IBM quantum computers and I run my circuit on qubits with the lowest readout error. However, I just obtain fidelity of the ...
- 121
1
vote
2
answers
182
views
Error while plotting the resulting distribution
I am using this code, as a test of my qiskit, but I am having errors on using the simulator
Building the circuit
We begin by importing Qiskit.
from qiskit import *
...
- 11
1
vote
1
answer
50
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Why does Lidar define a decoherence-free subspace as "a subspace that undergoes purely unitary evolution"
In this paper from 2014, Lidar defines: "an open system which undergoes purely unitary evolution (possibly only in a subspace of its Hilbert space) is said to be decoherence-free." Why is ...
- 131
2
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0
answers
42
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Controlled Ry gate on IBM and IonQ basis gates
As far as I know the basis gates for IBM and IonQ are:
IBM: ['cx', 'id', 'rz', 'x', 'sx']
IonQ: ['rx', 'ry', 'rz', 'rxx', 'id']
I used qiskit.transpile to see check how Controlled Ry gate can be ...
- 21
0
votes
1
answer
53
views
IBMProvider.load_account() AttributeError: type object 'IBMProvider' has no attribute 'load_account'
I am trying to resolve the below deprecation warnings I am getting while using IBMQ framework.
...
- 513
1
vote
1
answer
40
views
Can we de-decohere an open system?
Can a mixed state become pure due to its interaction with a vast environment? Certainly, a strange proposal, and yet let's take a diagonal matrix representing a mixed state, say $$\begin{pmatrix}
p_{1}...
- 111
0
votes
0
answers
113
views
How to calculate the state vector of a circuit using sampler().run()
I run a circuit using:
jobCircuit = Sampler(backend).run(circuit)
resultCircuit = jobCircuit.result()
How can I access to a state vector of the circuit? I tried ...
0
votes
2
answers
5k
views
IBMQ import error
I am trying to import IBMQ from qiskit. But I encountered following error.
...
2
votes
3
answers
843
views
Is there a way to use a fake backend for ibm_brisbane?
Is there a way to use a fake backend for ibm_brisbane?
I tried this but it is giving me the error that the backend is not present:
...
- 135
2
votes
1
answer
139
views
Hilbert space of n qubits always has a decoherence free subspace if n is even?
I've heard that a subspace of an $ n $ qubit Hilbert space is called decoherence-free if it is not affected by errors of the form $ g^{\otimes n} $ where $ g \in SU(2) $.
Let $ \textbf{2} $ denote the ...
- 4,936
0
votes
1
answer
105
views
Get the error of basis gates programmatically
I want to get the error rates of the basis gates of a backend. Is there a function that can achieve this functionality?
For example, I want the error rates of the basis gates rx, cx of ibmq_mumbai ...
- 135
1
vote
1
answer
493
views
QiskitBackendNotFoundError: 'No backend matches the criteria'
I am struggling with the QiskitBackendNotFoundError: 'No backend matches the criteria' even though I am able to see the backends available to me.
...
- 513
0
votes
0
answers
459
views
Ramsey Measurement for Characterising a Qubit
I'm trying to understand the Ramsey measurement used to characterise dephasing effects in qubits.
When operating on resonance, I understand the following quantum gate diagram to describe the $T_2^*$ ...
- 1
0
votes
1
answer
51
views
How the shots belonging to the same job are scheduled to run on IBM quantum devices?
How the shots belonging to the same job are scheduled to run on IBM quantum devices? Suppose my job has 1000 shots. Will all shots be executed in series, or is it possible they will be interleaved ...
- 228
1
vote
1
answer
291
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How is Quantum Computing expressed in the language of abstract algebra?
I've lately been taking further coursework in abstract algebra, and it has struck me as fairly reminiscent of quantum computing. Of course, Pauli matrices, etc. have relevant roots within abstract ...
- 21
1
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0
answers
63
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Interleaved Randomized Benchmarking experiment with custom PassManager
I have a custom PassManager, which calibrates a few gates in the circuit in the transpiler pass. I want to conduct an Interleaved Randomized Benchmarking experiment ...
- 135
3
votes
1
answer
769
views
Erasure errors in quantum error correction
Consider an $[n, k, d]$ classical code. This code can correct up to $d-1$ erasures. For example, if we have the code that maps $0\rightarrow 00$ and $1\rightarrow 11$, this code has distance $2$. ...
- 3,169
0
votes
1
answer
87
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IBM quantum composer possible bug?(state amplitudes of quantum circuit)
I have this quantum circuit:
and from the IBM quantum composer I get this state amplitudes:
I wanted to flip the target qubit and keep only its pure state however this is not what I am getting.I am ...
- 165
1
vote
0
answers
42
views
How to represent the gates and the quibit states in the 'Hello Quantum' iOS game in IBM Quantum Learning graphical simulator
The Hello Quantum ios game developed by IBM has the X, Z, H and CZ gates manipulating a 2 qubit array (im not sure if array is the right word?).
I want to know how I can represent the qubit states in ...
- 51
1
vote
1
answer
53
views
Is qiskit.pulse.SamplePulse deprecated?
I'm currently following along the book "Learn Quantum Computing with Python and IBM Quantum Experience" by Rodert Loredo and I am at chapter 8 - Generating pulse schedules on hardware. The ...
2
votes
0
answers
82
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Quantum Annealing on IBMQ using Qiskit-Pulse
Qiskit-Pulse is the analog level control SDK of IBMQ hardware. Is it possible to implement an adiabatic annealing protocol/algorithm on IBMQ hardware using Qiskit-Pulse?
Not asking about QAOA, which I ...
0
votes
1
answer
70
views
Frequency of qubits in qiskit simulators
I am trying to study the effect of dynamical decoupling sequences (Hahn Echo and CPMG) using qiskit's qasm_simulator with an added noise model from ...
0
votes
1
answer
65
views
Clarification on Definitions of Relaxation Probabilities
In the paper Modelling and Simulating the Noisy Behaviour of Near-term Quantum Computers, when the authors discuss relaxation times ($T_1$), they define two probabilities, $P_{T_1}$ and $p_{\text{...
- 867
1
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0
answers
34
views
ZNE for mitigating errors in probability distribution results
Can ZNE be applied to mitigate errors for getting the probability distribution in the computational basis rather than mitigating errors for calculation of expectation values?
- 135
4
votes
1
answer
275
views
Retrieving job result attributes in Qiskit
I am trying to optimize a Hamiltonian using QAOA in IBM Qiskit.
I used the following 'minimize' function to get my result. (I am not including the whole code because it will get unnecessarily long).
<...
- 53
1
vote
0
answers
80
views
In qubit phase tracking, does the phase $\delta$ have to be synchronized to the Larmor precession?
In many textbooks (e.g. LaPierre 2021 or Byrd 2022), when dealing with the physical implementation of quantum gates in spin qubits, Larmor precession is usually introduced first as a way to rotate the ...
- 21
1
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0
answers
44
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Running Pulse Schedules with different resilience levels
Is there a way to run a Pulse schedule with different resilience levels? I was thinking about passing the resilience level values in the options of Sampler primitive, but when I tried to run, it says ...
- 135
1
vote
2
answers
189
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Yet another condition for a map to be completely-positive and trace-preserving
Surely, these conditions are all well-defined and well-known (via the Choi, Kraus, and Stinespring presentations). Is the following 'definition' valid? Does it make sense?
"The map is CPTP if, ...
- 161
2
votes
1
answer
50
views
Is it possible to do the transpilation with a priori retired devices?
Is it possible to do the transpilation with "any" device in qiskit? I would be interested in doing this with already retired devices.
- 641
1
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0
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120
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An unexpected result of the Implementation of a finding minimum values algorithm using a qRAM
Motivated by the article Quantum algorithm for finding minimum values in a Quantum Random Access Memory, I'm training to implement a simplified version of the proposed algorithm. But the output isn't ...
- 11
0
votes
1
answer
132
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Are quantum simulation results more accurate than real IBMQ device results?
Getting two different results from simulation and rel IBMQ device. Which is more accurate?
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