Questions tagged [simulation]

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

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Anti-symmetrization on the lattice

Assume, I'm using a system of qubits to simulate a fermionic system. If I'm using the second-quantized formalism (e.g. orbitals in quantum chemistry), the anti-symmetric nature of the fermionic wave ...
mavzolej's user avatar
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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 ...
Ruth V.'s user avatar
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Trotter error for bosons in various encodings

Mapping second-quantized bosonic modes onto qubits can be done using various encodings. Each of those have their pro et contra. Fewer qubits — more gates, and vice versa. Encoding an $N$-level bosonic ...
mavzolej's user avatar
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5 votes
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OpenFermion to Qiskit

Is there a direct way to go from an object generated in OpenFermion to objects usable in Qiskit? I can't find anything about any plugin. It's not too hard to translate into pyQuil and then to Qiskit ...
Andrew Jackson's user avatar
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What is the current research status in simulating many-particle systems from first principles?

There is a huge gap between basic physical laws and predicting many particle systems from first principles. It will be so amazing if we can predict most properties of many particle systems (from mass ...
jw_'s user avatar
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Application of classical approximate optimization algorithm to bottlenecks of quantum computing

According to J. Gough, one of the bottlenecks in the current development of large-scale quantum computing may be the lack of our ability to simulate large scale quantum system, which is a NP-hard ...
Math.StackExchange's user avatar
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547 views

Error: Simulation of "Quantum algorithm for linear systems of equations" for $4\times 4$ systems on Quirk (without SWAP) - Global phase

Following @DaftWullie's answer I tried to simulate the circuit given in Fig. 4 of the paper (arXiv pre-print): Quantum circuit design for solving linear systems of equations (Cao et al, 2012), on ...
Sanchayan Dutta's user avatar
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103 views

Clifford element/tableau composition as matrix multiplication

Elements of the $n$-qubit Clifford group (or more precisely, elements of the projected $n$-qubit Clifford group, see Is the Clifford group finite?) may be represented as $2n \times 2n + 1$ binary-...
Surgical Commander's user avatar
4 votes
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117 views

Understanding the Gottesman-Knill Theorem

I come from a theoretical CS background, and I am trying to gain a better appreciation of the exact formal statement of the Gottesman-Knill theorem in terms that I am more familiar with. My question ...
trillianhaze's user avatar
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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 ...
Marsl's user avatar
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Expectation value of a time evolved circuit in the non-Z basis

I am new to qiskit and have hit a roadblock in my calculation. Given the following circuit: ...
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Qiskit: efficient way to create bound circuits?

I am running an optimization problem whose objective function $F(a)$ requires measuring N variational circuits $V_i(a)$ at each evaluation. So, roughly, I have created N parametric circuits and I do: <...
consthatza's user avatar
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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. ...
Marco Fellous-Asiani's user avatar
4 votes
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60 views

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 ...
Davide Rattacaso's user avatar
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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 ...
peachnuts's user avatar
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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, ...
haoyu's user avatar
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Could quantum computers answer the question of whether QCD predicts quark gluon confinement?

As I understand it, it is not known whether or not QCD actually predicts quark gluon confinement. As I understand it answering questions in quantum field theories is generally harder in terms of ...
Anders Gustafson's user avatar
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167 views

Matrix multiplication through Block Encodings

For a project, I want to simulate a matrix multiplication on a simulated quantum circuit. Assuming that we have a matrix $A\in \mathbb{R}^{m\times n}$ stored in a quantum superposition, i.e. $$|A\...
Thomas's user avatar
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What is the non-recursive form of the sum-over-paths simulation algorithm?

In my previous question on this, I managed to come up with a simple recursive algorithm for the sum-over-paths method. However, what other snatches of material I can find online don't use recursion ...
ahelwer's user avatar
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Simulating a Quantum Network over a real Classical Network Using Simulaqron

I'm trying to simulate a quantum network over a real classical network using the Simulaqron framework. I know the documentations says this is possible but I am having trouble finding examples of how ...
Scott Oshiro's user avatar
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32 views

Quantum Codes and Plasma Codes for Simulation Applications

I am wondering if anyone in here has heard/read is involved in quantum codes applied to simulate plasmas? I have read that PPNL is working on that but have not actually seen/found any of their ...
Enrique Segura's user avatar
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97 views

How to determine the minimum number of experiments needed to compute m-many k-local Pauli expectations?

Say I have an algorithm over N qubits and I want to find the expectation value of an operator $O$ composed of a sum of mterms, each of which is the tensor product of some number of single-qubit Pauli ...
forky40's user avatar
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Deutsch Algorithm on a Quantum Turing Machine

I understood how a Quantum Turing Machine works from this lecture. It would be great if someone could give an example of how this machine could be used to solve a real problem though, for example, ...
Mahathi Vempati's user avatar
3 votes
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30 views

How to have seperate registers from scrach?

I am very new to quantum computing, so this might be a really simple question. I am coding a quantum computer simulator in python from scrach and I'm not sure how to make registers work. I would just ...
Gytis Vejelis's user avatar
3 votes
0 answers
40 views

qiskit QAOA on Aer GPU giving errors

I am trying to run Qiskit QAOA algorithm on using aer simulator and device GPU. But I am not sure how to give this backend in the QAOA algorithm structure. Here is ...
to_batman's user avatar
3 votes
1 answer
82 views

Single-shot error correction for the surface code with measurement errors

I am trying to implement a single-shot error correction for the surface code with data + measurement errors (both with prob. p), using the (build-in) BP+OSD decoder. I am mostly following these papers:...
David Dentelski's user avatar
3 votes
0 answers
37 views

Advantage of quantum computers over classical computers in fully modeling interactions between atoms?

I'm trying to better understand the advantage quantum computers offer in terms of their ability to more accurately model chemical reactions. As a way to come to a deeper understanding, my question is: ...
Poe's user avatar
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3 votes
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33 views

Compiling pulses with time dependent $\sigma_x$ and $\sigma_y$ control

I have a Hamiltonian of the form: $$ H = c_x(t) \sigma_x + c_y(t) \sigma_y$$ and I want to compile a pulse "P" that has both $\sigma_x$ and $\sigma_y$ control, with different time dependent ...
Annie's user avatar
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98 views

"Wn state" in Bravyi-Kitaev encoding

For a particular simulation, I need the initial (physical) state of the QC to represent the equal superposition of all single-occupancy fermionic second-quantized states. In Jordan-Wigner encoding, I ...
mavzolej's user avatar
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3 votes
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How many cores and what processors are used in the cloud ibmq_qasm_simulator?

Cloud IBMQ simulator ibmq_qasm_simulator can process up to 32-qubit circuits quite fast. However, I could not find any information about the simulator backend properties, e.g. how many cores, what ...
Michael's user avatar
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3 votes
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126 views

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 ...
v-joe's user avatar
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2 votes
0 answers
34 views

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 ...
Carlos Murilo Romero Rocha's user avatar
2 votes
0 answers
85 views

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 (...
stopper's user avatar
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2 votes
0 answers
48 views

Quantum circuit runtime

I want to estimate the execution time of some experiments, and I would be interested to know how the time needed to run a quantum circuit grows in function of the number of qubits and the parametric ...
barrieta's user avatar
2 votes
0 answers
40 views

Quantum algorithms with few T gates?

Many existing quantum algorithms require millions or billions of T gates to reach a scale that is classically hard to simulate. However, existing Clifford + T circuits seem hard even with 100 or so T ...
shixian105's user avatar
2 votes
0 answers
50 views

Simulation of algorithms with QFT on a classical computer

In paper The Quantum Fourier Transform Has Small Entanglement the authors showed that strong entanglement of qubits caused by QFT comes mainly from ordering the qubits. QFT itself prepares only weak ...
Martin Vesely's user avatar
2 votes
1 answer
146 views

Computing gradients in parallel with cost from probs (Pennylane-Braket)

Do circuits that measure probabilities instead of expectation values benefit from parallel execution? The Computing gradients in parallel with Amazon Braket tutorial shows how the multiple device ...
ryanhill1's user avatar
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2 votes
0 answers
133 views

Parallel run of qiskit circuits

I am trying to run simulation instances of a parametrized circuit in parallel but my algorithm is extremely slow. Excuse my ignorance, but I just want to be sure that the circuits are indeed running ...
consthatza's user avatar
2 votes
0 answers
32 views

Clasically-simulable MBQC pattern for a BQP computation

I'm looking for an example of an MBQC pattern which performs a BQP computation and ideally has been used in research before. The pattern should be classically simulable (i.e. containing in the region ...
T.H's user avatar
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268 views

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 ...
Yousef Zook's user avatar
2 votes
0 answers
25 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 ...
Quantum Guy 123's user avatar
2 votes
0 answers
66 views

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: ...
Will Yang's user avatar
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2 votes
0 answers
59 views

What are the evidences that quantum simulation have a future?

Here future means orders of improvement which can solve rather different problems e.g. emergent phenomenon. For example, the first integrated logic only have several transistors, now it have billions ...
jw_'s user avatar
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2 votes
0 answers
141 views

Accuracy of rotational gates on IBM Quantum

As a computer memory is finite, it seems reasonable to assume that a rotational angle of gates $Rx$, $Ry$ and $Rz$ (and $U1$, $U2$ and $U3$ gates as well) has some smallest step which can be ...
Martin Vesely's user avatar
2 votes
0 answers
22 views

Efficient simulation of linearly assembled Quantum States

In this paper section 4.2 the author describes how to efficiently simulate linearly assembled quantum states. When describing the procedure to do so the author shows the following circuit: The ...
Bertrand Einstein IV's user avatar
2 votes
0 answers
175 views

How accurate are Qiskit’s unitary and Statevector simulators for very large circuits?

Background: I wrote a code that takes a Qiskit circuit C as an input and outputs a random circuit C’ such that C and C’ have the same unitaries. I tested my code using Qiskit’s Statevector simulator ...
simulationsareawesome's user avatar
2 votes
0 answers
98 views

Length / transpilation issues with Grover's algorithm

I would like to discuss the discrepancies between what we see in the simulator versus what we see in the actual running of the code on any IBMQ machine for any qubits at 5 or above. I am doing a final ...
Joel Anthony Collins's user avatar
2 votes
0 answers
156 views

What Are The Most Promising Real-World Applications For Quantum Machine Learning

I know this has been asked before in different ways, however, I am interested in something with a degree of clarity and focus not found in other questions. What I am looking to get is a list of the ...
Darien Schettler's user avatar
2 votes
0 answers
62 views

How to get the $T1$ specs for the Rigetti's quantum processor (Aspen 7)

I am trying to find the $T1$ coherence time for different qubits of Rigetti's quantum processor (Aspen 7) using Python. I tried using Specs() but encountered an ...
SHASHANK RANU's user avatar
2 votes
2 answers
576 views

VQE Cirq example

Is my understanding correct that in this example the Hamiltonian measurement is not performed through measuring individual Pauli operators because all its terms are mutually commuting? So, for each ...
mavzolej's user avatar
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