Questions tagged [noise]
For questions about different types of noise a quantum computer (or qubits) may experience; how this affects the outcome of the computation; how to reduce a specific type of noise on a specific implementation of quantum computer; or how to simulate noise.
69 questions with no upvoted or accepted answers
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Add noise_model when using 'ibmq_qasm_simulator' backend and provider.runtime.run() function
I am trying to test some qiskit code that employs readout-error mitigation using the ibmq_qasm_simulator backend and Qiskit Runtime. I am getting the backend as ...
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191
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Apply a single-qubit channel between in between two circuits in Qiskit
Suppose, you have two parts of a circuit in Qiskit, qc1 and qc2 on any number of qubits such that the entire circuit is given by
...
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How is Pauli twirling applied to a noisy gate in practice?
My understanding of Pauli Twirling mainly comes from this paper. Please, correct me if I am wrong in any part of my explanation.
General idea of Pauli twirling
The idea of Pauli Twirling is the ...
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How does it work QasmSimulator with the option "density matrix"?
I am making some simulations on IBM Quantum Lab and as backend I tried to use QasmSimulator(method = "density_matrix") in order to simulate noise. I wanted to know how this method works in ...
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Does noise model in qiskit impact the optimized parameters for QAOA?
I have read this paper about the effects of quantum noise on QAOA.
In the conclusion, it says: QAOA is a noise-tolerant algorithm, quantum noise does not change the QAOA quantum circuit parameter ...
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What types of noise are there?
I know this does vary to some extent from implementation to implementation, but I'm looking for broad 'classes' of noise.
For example, I know a very common source of noise/error is the environment - ...
- 3,469
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480
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Implementing a depolarizing channel for 2 qubits on IBM Q
I am trying to use IBM Q to perform the following depolarizing channel on a state of 2 qubits $\rho=|\psi \rangle \langle \psi |$:
$$\rho \to (1-\lambda)\rho + \frac{\lambda}{4}I$$
This is within ...
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Examples of temperature-dependent quantum channels
I am looking for examples of instances or families of quantum channels that arise out of an interaction of a quantum system with an environment having some temperature. For instance, the generalized ...
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2
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515
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Readout Error in Qiskit: What is a reasonable model?
The Readout Error in Qiskit is described here: https://qiskit.org/documentation/stubs/qiskit.providers.aer.noise.ReadoutError.html
Although it is easy to obtain such an error for 1-qubit for IBMs ...
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What are the possible gates that I can use to vary input states before CNOT?
We know that the noise of the $\text{CNOT}$ gate varies depending on the input state before it.
What are the gates that I can put in the place of the 4 identity gates above to change the input state ...
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Why are two qubits gates more noisy?
I would like to understand why two qubit gates are generally more noisy.
If I am interested in single qubit gates, I can have an effective modelling as a master equation:
$$\dot{\rho}=\frac{1}{i \...
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What are reasonable noise/dephasing parameters for QuEST to emulate state-of-the-art quantum computers?
The QuEST code allows for simulation of quantum computers taking dephasing and depolarizing noise into account via one and two qubit dephasing and depolarization. What are realistic parameters for ...
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What do you specify when you physically apply a unitary?
In the Environment and Quantum Operations in Nielsen and Chuang, section 8.2.2, they say that when you apply a unitary on a state, you expect the output as the just the state transformed by the ...
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Does self-induced collapse limit the size of a quantum computer?
This question is related to this question, but I'm specifically interested in self-induced collapse. Suppose that the size of a quantum system alone somehow leads to a projection of the state (a "...
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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 ...
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In hetero (homodyne) detection, what does it mean to operate at the quantum shot limit?
I am an electrical engineering by trade, working on the analogue part (Transmitter & Receiver) of a quantum optical communication channel. By this, I mean I have not much experience on things ...
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How is coherent noise more detrimental than incoherent noise for QEC when QEC is supposed to decohere noise?
It's sometimes mentioned that unitary, coherent, noise can adversely impact the performance of QEC codes compared to purely stochastic Pauli noise. This motivates protocols such as randomized ...
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Improve accuracy of fake backends while remaining realistic
If I run the code
backend = FakeLima()
nm = NoiseModel.from_backend(backend)
print(nm.__dict__.keys())
I get the following output:
...
- 513
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Qiskit noisy FakeManila simulator + ZNE
I am trying to run a simple VQE calculation on H2 using FakeManila noise model and ZNE for error mitigation; see code below. The problem is that I can never reach not even close the ground electronic ...
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Most efficient way to calculate an expectation value of a noisy model in Qiskit
I want to classically simulate quantum circuits with noise. This noise can be a custom one (noise.NoiseModel()) or a fake quantum computer (...
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Exploiting virtual-$Z_{\theta}$ corrections in QEC
The work done by IBM Researchers to perform virtual-$Z_{\theta}$ gates allowed them to:
achieving zero-time relative phase shifts;
correcting $Z_{\phi}$ errors occurring when applying some gates -- e....
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Qubit Resource Estimates for 2D Ising Model
I recently came across this paper where the 1d Transverse Field Ising Model (TFIM) with $n$ spins was simulated on a quantum computer. The estimated resources were $n^2$ for the number of gates and ...
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380
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Does Qasm Simulator add noise by default?
I am wondering if Qiskit QasmSimulator adds noise by default or not. I am asking because I have 2 circuits:
circuit 1: computes cosine similarity between two vectors
circuit 2: computes cosine ...
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How do you quantify the figurative 'cost' of a quantum circuit
Many gates are not available on a real computer and therefore the circuit must be transpiled into a specific set of gates. I have seen this equation below which is used to to determine the 'cost' of a ...
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understanding final state of a QPU interacting with the environment
As stated in UT's QML course for a QPU that is interacting with the environment:
The environment is defined by a temperature $T$, and if we let the
system equilibrate, the QPU will become thermalized ...
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How to turn a 'term' in a QuantumError into a QuantumError?
A QuantumError class may have many terms, and we can use .error_term(position) to have a look at each term. But it returns a list instead of another QuantumError ...
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227
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Iterative Phase Estimation with noise vs standard Quantum Phase Estimation with noise
I am doing Qiskit Lab 4 about Iterative Phase Estimation. I created a circuit implementing IPE for theta = 1/3 (phase of 2pi/3). Here's the circuit:
It seems to do okay if I run it without noise in a ...
2
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62
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Frequency collision and crosstalk error
As the number of qubit increasing, the frequency of qubit will be crowded and there will become the frequency collision. I was wondering that is there any relation between frequency collision and ...
- 1,423
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48
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Dealing with noise in NISQ
I wanted to know if there are some way in NISQ (we run "bare" gate without Q.E.C) to certify if an algorithm will give a correct or wrong answer based on the process of a single gate ?
For example in ...
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What noise channel that is not coming from the control can lead to XY qubit rotations?
In a semiclassical treatment, the noise Hamiltonian of a quantum system can be treated as a summation over its noise channels in the following way:
$$\hat{H}_{\text{noise}}=\sum_{k}\beta_{k}\left(t\...
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What are efficient methods for measuring gate noise?
In this question I'm concerned with getting detailed spectral information about analog noise in quantum gates.
Assume we have imperfect control over transitions between $\vert 0\rangle$ and $\vert 1\...
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How to apply circuit cutting to MCX gates?
I am working on a quantum version of a fuzzy controller (https://ieeexplore.ieee.org/document/9869303). This inference engine is implemented with a quantum circuit composed of X and MCX gates as in ...
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Applying 2-qubit noise to a multi qubit system using local operations in Python
I am trying to create a simulation of 2-qubit dephasing noise that acts on the first two qubits of a multi qubit system. I would like to do this locally rather than expanding my kraus operators into $...
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How to implement frequencies (drive,measuring) and temperature in a qiskit Noise Model?
Im trying to build a qiskit Noise Model but the NoiseModel() class does not admit temperature, frequencies or measuring time.
I thought about using the pulse ...
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VQLS behaves badly under simulation with noise
I was studying VQLS in https://qiskit.org/textbook/ch-paper-implementations/vqls.html and since I could not understand the circuit created by the new Hadamard test (...
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How to model the IBM quantum errors?
I'm conducting a study of the quantum channel errors, and a question has arisen: Is it possible to model the errors of an IBM quantum computer with Kraus operators?
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46
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Completeness relation of kraus operators not satisfied in Fake backends
With the following code
...
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How is Pauli twirling so powerful?
So the Pauli twirling approximation gives us a quantum channel $\Phi$ that transforms a density matrix $\rho$ to:
$\Phi(\rho)\mapsto\sum_{i=0}^3 \sigma^i \rho \sigma^i,$
where $\sigma^0 = \mathbb{I}, \...
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Is there a way to implement a noisy CNOT gate using CUGate in Qiskit
Wondering if there's a way to implement the noisy version of CNOT (or CX) gate via CUGate using qiskit library for a given fidelity p?
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How to manipulate thermal relaxation noise in Qiskit model?
I am trying to experiment with various values of T1 and T2 parameters in thermal relaxation noise.
...
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What does adding depolarizing error on a Hadamard gate mean mathematically?
I have a quantum circuit as the following picture. Now I add the depolarizing error on the Hadamard gate using the following code in Qiskit.
...
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Representing 1 qubit pauli-channels as an averaging effect of random rotations in the bloch sphere. Basic literature?
I am looking into 1 qubit pauli channels, e.g. the dephasing channel
$$\mathcal{E}(\rho)=(1-p)\rho+p\sigma_z\rho\sigma_z.$$ I found out it could be represented as
$$\mathcal{E}(\rho)=\int p(\lambda)\...
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Zero noise extrapolation for error mitigation: Meaning of rescaled density matrix, specifically when there is no local hamiltonian evolution
I have a few questions regarding dynamics rescaling for zero noise extrapolation. In the paper Error mitigation for short-depth quantum circuits, in equation (30), they write
We redefine $T \...
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noise and classical bits (measurements ) in qiskit
I am using qiskit and LocalNoisePass to add custom noise to the gates. But there is a problem when there are classical bits in the circuits. The localNoisePass give this error
...
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Why my noise model acts different on my VQE circuit compared to a simple circuit
I have created a noise model which uses depolarizing error and I add it using the add to all qubits quantum error command. I also use readout error and add that using the add to all qubits readoute ...
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what is Pauli twirling approximation?
In this video, Artur Ekert shows that for a single qubit, 4 Kraus operators can be chosen such that the action on state $\rho$ is given as $\rho \rightarrow \sum_m p_m A_m \rho A_m^\dagger$. We can ...
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Copying a reduced noise model from an IBM device
I need to use the noise model coming from a large IBM device. Nonetheless, I do not need to use the whole Noise Model. I only need the information of let's say qubits [10:15] and [20:25]. That would ...
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How to merge logical computation with encoding-decoding schemes
Usually QEC is treated in two different ways.
Definition of a logical computation with a non-destructive QEC scheme
Definition of a encoding-decoding scheme with destructive measurement after ...
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What causes the random variations in the probabilities with respect to the theoretical values, in IBM and QASM simulators?
When I measure 2 and 3 qubits after putting H gate on all of them, there is a variation in probabilities of results in comparison with theoretical values (25% and 12.5%, respectively).
This occurs on ...
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Do we expect similar results in form of measurement histogram for both (1 run with 100 shots) and (100 runs with 1 shot each)?
100 runs of 1 shot each were executed one by one over a single qubit initialised with 0 (default) and no quantum gate implemented on top of it. All measurement results were found to be noise free i.e. ...
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