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# Questions tagged [simulation]

For questions about simulating either quantum computers or simulating things on quantum computers.

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### Why use superpositions to write states even when they are not entangled?

I am reading book "Dancing with Qubits. How quantum computing works". I had learned the rule of entangled state: when quantum state is separable(i.e. it can be written as such a tensor ...
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### Why do we need physical qubit if qubit can be simulated?

I do not see any advantage in constructing very costly and imperfect physical qubit while this qubit can be simulated with using conventional computer memory (noise-free). So what is the purpose when ...
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### what is difference between the following two results

If this question sounds trivial please bear with me as I am beginner in QC. Code 1 ...
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1 vote
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### How to simulate $H(\theta) = B(\sin\theta S_1^x +\cos\theta S_1^z +\sin\theta S_2^x +\cos\theta S_2^z)+aS_2^zI_z$ on IBM Qiskit

I am trying to simulate this Hamiltonian on IBM Qiskit, for varying values of $\theta$: $H(\theta) = B(\sin\theta S_1^x +\cos\theta S_1^z +\sin\theta S_2^x +\cos\theta S_2^z)+aS_2^zI_z$ Where S is ...
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### What are the main approaches allowing to efficiently simulate quantum circuits, and which hypotheses those circuits have to fulfill

In general, it is very computationally intensive to simulate the evolution of a quantum system. However, in some particular cases, an efficient classical simulation of a quantum algorithm is possible. ...
31 views

### Why does VQE with pennylane and scikit-optimize gp_minimize give 'func must be scalar' error?

I am trying to replace the SPSA optimizer in the VQE tutorial of pennylane by the bayesian optimizer of scikit-opimize. When running the code below I get the error "func should return a scalar&...
37 views

### Quantum Annealing vs Quantum Monte Carlo: can QMC do all that QA can?

I'm working on an essay about quantum technology, and the connection between the annealing algorithm and quantum computing hardware is an important transition in the text. I'd like to know if there is ...
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### Gottesman Knill theorem - why $O(n)$ operations for **arbitrary** *unitary* gates

My question is closely related to this one but the answer focused mainly on measurements while my question is for unitary Clifford operations: why do we need $O(n)$ operations to update a quantum ...
19 views

### What is a realistic model for simulating physical tampering of a channel? (ex: nearby vibrations)

Somewhat related to this question. Imagine a fully functioning quantum network, where qubits are transported via fiber optic cable. If vibrations were to physically tamper with a channel in such a ...
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### Recommendation for Efficient Lindblad Simulator Packages

Could anyone recommend some efficiently established packages to simulate Lindblad dynamics? I wrote some codes using numpy to solve the vectorized superoperator equation but it's rather slow. Update: ...
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### Enable qiskit backends in google colab

I am trying to enable backends by using qiskit.IBMQ.backends() methods in google colab. but it is showing error. How to enable this? AL time this backend showing an error. i have tried by using some ...
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### why does this definition of multi qubit Clifford Tableaus not pass symplectic test?

I am attempting to write a module for composition of Clifford Tableaus using only elementary arithmetic and logical operations. Everything seems to be working fine, except that as far as I understand, ...
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### Framework for PEPS of Surface Code

I am reading this article about the implementation of Surface Code with noise in PEPS tensor network. I am looking for a framework/library (preferred python) that is the nearest for such an ...
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1 vote
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### Platform to Simulate FLO of Majorana

Is there any python (other languages are also OK) library/platform/toolbox, open-source, to simulate Majorana in FLO (Fermion Linear Optics) as done in this article. I tried to look for the platform ...
• 821
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### Why am I able to simulate such high qubit numbers on my laptop?

Recently I've been working on a VQE-related project, for which I'm using Qiskit's TwoLocal variational form (qiskit version 0.34.2). I noticed that I was able to simulate this circuit up to ...
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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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### How to simulate the state of a system after partial measurement?

Based on the answers at here and here, I have a quantum simulator which implements the operations described in the classic Teleporting an Unknown Quantum State. Careful comparison of circuits with the ...
• 625
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### Why the pulse scheduler produces a different output from the original circuit?

As part of a larger code, I have to convert a quantum circuit into a Pulse scheduler. The problem is that the scheduler output is incompatible with the circuit output. In particular, the difference ...
77 views

### How to order results after multi-circuit qiskit.execute parallel run?

I'm kinda new to qiskit and I find really fascinating its parallelization capabilities, then I'm trying to creating all the needed circuits for my application at once and transpile, assemble and ...
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1 vote
79 views

### What does a statevector with 3 elements (in Qiskit) represent?

I wasn't quite sure where to post this as I don't know if this is a Qiskit specific thing or not, but I'm not sure how to interpret this result I got from running a simulation. from result.data(): <...
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### Simulators vs Real Backends

I am using Qiskit to run some circuits and a question arises in my mind. I know that when we run in the simulators we are running in "ideal" environments. This means there is no noise that ...
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134 views

### What is the fastest classical simulator for quantum circuits with only Clifford gates?

What is the fastest classical simulator for quantum circuits with only Clifford Gates? And is there any "friendly" implementation e.g. in Python (or in some well-known libraries like Qiskit)?...
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### Is it possible to set quantum volume in IBM Quantum simulator?

A quantum volume serves as a metric of a quantum processor quality. So far, IBM Quantum provides processors with quantum volume up to 128. Freely accessbile processors have QV up to 32. A user using ...
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1 vote
43 views

### Simulating readout errors on aer simulator

I'm trying to simulate quantum experiments using a customized noise model. Here's my code: ...
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### Is the SWAP gate a Clifford Gate? How would I express it using the Clifford Gate generators?

By my calculations, it looks like the SWAP gate is a Clifford Gate. See the following table: I follow the same method as in this paper for showing a gate is a Clifford Gate. I got the above table by ...
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### How is Quantum Phase Estimation useful for simulating dynamics of a many-body system?

I am quite aware of the Quantum Fourier Transform (QFT) as well as the very closely related topic of Quantum Phase Estimation (QPE). The latter is usually motivated as follows: Given a unitary $U$ and ...
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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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### Roughly speaking, How many qubits will be needed to study (or simulate) a molecule such as: C29H31N7O?

It is often said that one of the early applications for Quantum Computers will be drug discovery. Q: Roughly speaking, How many qubits will be needed to study (or simulate) a molecule such as: \$C_{29}...
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36 views

### Any simulator packages for quantum annealing/adiabatic quantum computation?

Are there any simulator packages for quantum annealing/adiabatic quantum computation, like Qiskit Aer but for quantum annealing? There seems to be only classical heuristics in D-Wave Ocean package, ...
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1 vote
73 views

### How can I get the results from simulating noise models?

I'm trying to run some simulations of my quantum circuits using qasm simulator. I first tried to import the noise data from a quantum device and then use that information on qasm. Here's part of my ...
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### Calculating measurement probabilities from a quantum circuit

Currently I'm trying to calculate the circuits I'm building and show that they work as intended. Somehow, my measurments do not, at all, represent my calculated expectancies. This is my circuit in <...
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### Difference between Aer.get_backend('aer_simulator') and AerSimulator()

In Qiskit, there are several ways to choose simulator: one is from qiskit import Aer backend = Aer.get_backend('aer_simulator') result = backend.run(circ).result() ...
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### How to import a generic stabilizer code in stim

I just started using stim to simulate the performance of quantum error correcting codes. I hope this is the right place to ask questions about the subject. The example code with the repetition code ...
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86 views

### Random circuits with google cirq

For my dissertation I need to simulate random circuits and I have been trying to use google Cirq for that. Looking at the documentation I have seen how to create my own circuit and simulate it, but it ...
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