Questions tagged [simulation]
For questions about simulating either quantum computers or simulating things on quantum computers.
180
questions
1
vote
0answers
16 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 ...
6
votes
2answers
96 views
Explicit states with high $T$ count
It is well known, that the Clifford $+T$ gate set consisting of the gates $\lbrace H, S, CNOT, T \rbrace$ is universal for quantum computation, that is, for any n-qubit unitary $U:\left( \mathbb{C}^2\...
0
votes
1answer
44 views
How can I simulate the Avg CNOT Error on IBMQ Backends?
I want to know exactly how to estimate the Avg CNOT Error rate for IBMQ Backends?
For instance, I tried to estimate the Avg CNOT Error rate for Belem Backend; I randomly prepared the 00,01,10,11 ...
2
votes
1answer
47 views
What is the maximum number of qubits that can be simulated by Qiskit using any method?
I'm looking to write an algorithm (potentially) using Qiskit, and am trying to find out what the maximum number of Qubits is that Qiskit can support with various simulation methods.
From reading other ...
4
votes
1answer
92 views
Is a black-box gate whose output is conditional on the value of an input amplitude possible?
Suppose we have a qubit in the state $|q\rangle = a |0\rangle + b |1\rangle$, and another ancilla qubit $= |0\rangle$.
I wish to have the following black-box gate:
...
3
votes
1answer
44 views
Which single fixed unitary can be used to efficiently simulate arbitrary quantum circuit?
Let $|p\rangle|00\ldots0\rangle$ be an initial (basis) state, where $p$ is a binary encoding of the circuit to be simulated and zeros are the working space. We apply some fixed unitary transformation $...
3
votes
2answers
377 views
How can I specify the qubits on quantum computers that I want to use?
Suppose I have the following 2-qubit quantum circuit:
...
3
votes
1answer
54 views
How to create CNOT from an entangling gate and arbitrary single-qubit gates?
I am working on the classical simulation of quantum circuits. I know how to efficiently implement the following entangling gate, which -- in the following paper: https://arxiv.org/pdf/1803.02118 -- ...
1
vote
1answer
60 views
Why does entanglement complicate quantum simulation?
To model a single qubit one would need enough memory for $2$ complex numbers. If we have an $N$ qubit system, we would have to store $2N$ complex numbers.
The general statement is that to store an $N$-...
3
votes
1answer
76 views
When and how do we use basis embedding?
It is suggested in various sources that a possible approach to representing classical data as a quantum state is simply to take the binary sequence $x$ and turn it to $|x\rangle$ (i.e., "basis ...
3
votes
1answer
80 views
Why does running my circuit on Quantum Hardware produce such unexpected resultss?
I am using Jupyter Notebook with Qiskit.
I have created a program that can add two 3-bit numbers together. When I simulate this program on a qasm_simulator it works as expected and I can add any two 3-...
5
votes
1answer
92 views
What is the superop simulator in Qiskit for?
I'm trying to understand what the use case of a superop simulator would be. My understanding is that density matrix is generally more resource intensive than state vector, but it has additional ...
2
votes
0answers
68 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 ...
4
votes
1answer
146 views
'Best practices' for making Stim run as fast as possible?
I'm currently testing out an error-correction surface code circuit in Stim.
I've tried a 19x19 surface code over 10k rounds of syndrome extraction sampled 256 times, and this takes about 165 seconds. ...
1
vote
1answer
51 views
What is the largest reported number of qubits used in a VQE simulation?
Numerous studies have investigated the simulation of an X-qubit circuit, demonstrating the 'classical simulation supremacy' on supercomputers. X is less than 50. However, useful VQE circuits are often ...
1
vote
2answers
131 views
Measuring entanglement entropy using a stabilizer circuit simulator
I'm trying to simulate stabilizer circuits using the Clifford tableau formalism that lets you scale up to hundreds of qubits. What I want to do is find the entanglement entropy on by splitting my ...
1
vote
1answer
36 views
How do I export the rightmost state of circuit wires (qbits and cbits) in a qiskit simulation
qiskit has a quantum teleportation tutorial which winds up with this simulation code:
...
1
vote
1answer
52 views
Setting the Initial State of Density Matrix Simulation in Cirq
I am trying to use the DensityMatrixSimulator in Cirq. I want to append gates to the circuit conditional on measurements. In order to reduce computational resources, I am trying to run these ...
0
votes
1answer
140 views
Memory Requirements for Qiskit Aer Simulator
I'm trying to work out how much memory is used for simulations of different sizes using the Aer simulator.
Here are my calculations:
$$ \text{Number of Qubits} = n $$
$$ \text{Number of Amplitudes} = ...
5
votes
1answer
138 views
What's the state-of-the-art to calculate $|Ab\rangle$, given a matrix $|A\rangle$ and a vector $|b\rangle$ in QRAM encoding
Assuming that we have a matrix $A\in \mathbb{R}^{m\times n}$ stored in a quantum superposition, i.e.
$$|A\rangle= \frac{1}{\|A\|_F}\sum_{i,j=0}^{n-1}{a_{ij}}|i,j\rangle$$
and a vector $b\in \mathbb{R}^...
2
votes
0answers
64 views
Matrix multiplication through Block Encodings
For a project, I want to simulate a matrix multiplication on a simulated quantum circuit. Assuming that we have a matrix $A\in \mathbb{R}^{m\times n}$ stored in a quantum superposition, i.e.
$$|A\...
3
votes
2answers
113 views
Statevector Simulation of QAOA always finds exact solution
My question is simple: does applying QAOA with a statevector simulation always result in a perfect solution?
I'm trying to calculate the best $\gamma$ & $\beta$ that solve certain problems but my ...
4
votes
0answers
63 views
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 ...
0
votes
0answers
54 views
Types of Quantum Computer [duplicate]
I am confused of all that different Quantum computers.
please correct me if I say something wrong.
There are two main different types of quantum computing:
Quantum Gates based computing
quantum ...
2
votes
1answer
43 views
Simulating QPE + Grover using Low-Rank Stabilizer Decomposition
I want to simulate a 40-45 Qubit circuit that applies Grover + QPE.
I've tried running a simulation on qiskit but can't really go past 18 qubits on my machine. As an alternative, I've been reading ...
3
votes
1answer
71 views
Get the gates after fusion optimization in Qiskit statevector simulator
I tried to obtain the gates after fusion in Qiskit-aer statevector simulator. What I can find now is that it provides a backend option saying fusion_verbose (bool): Output gates generated in fusion ...
3
votes
1answer
49 views
noisy circuit by openfermion
I am working on designing quantum error mitigation algorithms for simulating chemical systems. Therefore, a necessary component is to add noisy to the ideal circuit when using a quantum simulator. But ...
6
votes
1answer
192 views
Q# Simulation Behavior
I am attempting to run a series of tests on a Q# program I'm running on the local simulator, but I'm not seeing any way to use >1 shot and collect the results of those shots at once, as in ...
2
votes
1answer
117 views
No. of bits in 160 qubits computer [duplicate]
I read in a book that (https://hub.packtpub.com/quantum-expert-robert-sutor-explains-the-basics-of-quantum-computing/)
160 qubits (quantum bits) could hold $2^{160} \approx1.46\times 10^{48}$ bits ...
3
votes
1answer
65 views
Applications of Quantum Computing to Economics
I have recently been interested in the field of 'Econophysics' which as I understand it is the practice of basically applying results of physics in areas such as non-linear dynamics and stochastic ...
2
votes
1answer
142 views
Job fails when using PulseSimulator: Job Status: job incurred error
I'm trying to simulate a basic circuit using the PulseSimulator in Qiskit. The following Qiskit Pulse code works when I run it on the real device, but not when ...
1
vote
1answer
159 views
Simulate a quantum channel with a certain fidelity
I am looking for an easy-to-use framework for simulating a quantum channel that can accept the desired average fidelity of the channel as input.
For example, if I want a channel with 98% average ...
6
votes
1answer
134 views
Are almost-Clifford circuits almost easy to simulate?
Circuits consisting entirely of Clifford operations in $\{X, Y, Z, H, S, \text{CNOT} \}$ are "easy" to simulate classically since there is a method that can fully compute such circuits over $...
1
vote
0answers
95 views
How can I fix the BrokenProcessPool error in Qiskit?
I'm running a set of quantum circuits using the ibmq_qasm_simulator. However, sometimes my code works for the simulation, but sometimes it doesn't, and the system ...
1
vote
1answer
81 views
Trying to perform Quantum Phase Estimation on T-gate
I'm trying to perform QPE on the T-gate in Quirk but I'm not getting the correct result. For the T-gate, I should be measuring (001) with 100% probability, but instead, I'm getting the following:
I'...
6
votes
1answer
172 views
Trying to understand this measurement of a simple quantum circuit
It's a newbie question, I know. But I was just wondering if someone could help me understand why this simple circuit results with the measurement shown. I've just didn't get the last step. It's not ...
3
votes
0answers
64 views
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 ...
1
vote
1answer
38 views
Is there a faster way to get 'a list of' result from 'a list of inputs'?
I had a question about obtaining the probability of a certain state from the histogram, still using this example, suppose there's a variable in my quantum circuit, it's values are stored in an 'np....
2
votes
1answer
71 views
Is it possible to construct Grover search from Clifford gates only?
In the article Is Quantum Search Pratical the authors emphasized that a complexity of an oracle is often neglected when advantages of Grover search are discussed. In the end, a total complexity of the ...
4
votes
2answers
148 views
What is the “sum-over-paths” picture of quantum computing?
In chapter 9 of Scott Aaronson's book Quantum Computing Since Democritus (see online progenitor lecture notes here), he introduces a strange (to me) conceptualization of applying two Hadamard-like ...
1
vote
0answers
65 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 ...
2
votes
1answer
71 views
Computation of qubits with quantum gates using density matrix form
I'm making a quantum circuit with qubits and quantum gates. While I'm doing it, I have some problem with it. My calculation process is below.
As you can see, start qubit is $|0 \rangle$ and after 'X' ...
2
votes
1answer
250 views
Qiskit “statevector_gpu” method not available
I am trying to use the statevector_gpu simulation method in Qiskit Aer (see this page). I installed qiskit-aer-gpu according to ...
1
vote
1answer
51 views
Qiskit BasicAer simulator options
I usually use Qiskit "Aer" to simulate quantum circuit with several methods such as statevector, density_matrix, ...
2
votes
1answer
186 views
Qiskit BasicAer & Aer
While I'm simulating grover's algorithm, I found that with BasicAer backend it works well but with Aer it is not. What is the difference between ...
3
votes
4answers
83 views
Where can I get circuits of interest to quantum chemistry to try and simplify?
I am a computer science undergraduate working on a project in simplifying quantum circuits (using the ZX-calculus). I was hoping to try to simplify some circuits of interest rather than randomly ...
3
votes
2answers
580 views
How is a quantum simulator able to simulate a quantum mechanical properties on a classical computer?
I'm confused as to how a classical computer can simulate quantum mechanical properties through the use of classical bits. Why do we need quantum computers if a quantum simulator can do it's job on a ...
3
votes
2answers
86 views
What is the best approach for classically simulating quantum devices?
Now I'm focusing on quantum simulation (especially on classical supercomputers), but I saw there exist so many simulators. Is there any criteria to judge which is the best?
https://www.quantiki.org/...
0
votes
1answer
82 views
Inconsistency in Qiskit Aqua CircuitSampler from Operator Flow
I am trying to wrap my head around Qiskit Aqua Operators and I stumbled upon this:
My code
...
1
vote
1answer
55 views
Why is the lowest energy important to simulate a quantum system?
Quantum computers promise that they will simulate complex quantum systems, and I keep hearing that finding the ground state of that system (using for example Variational quantum eigensolver) is ...
