Questions tagged [simulation]

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

Filter by
Sorted by
Tagged with
1
vote
2answers
142 views

How to calculate the probabilities of observing quantum states using the “expectation_from_wavefunction” in cirq (and why)

I am currently simulating some quantum circuits, and want to calculate the probabilities of observing each individual state. I am able to use Cirq for this, and calculate it using $P_{00} = |\alpha|^2$...
1
vote
2answers
107 views

Normalization of the quantum state in Cirq

My understanding, for instance from this youtube video, is the following: Assuming a state $\psi = \alpha |0\rangle + \beta |1\rangle$, where $\alpha$ and $\beta$ can be complex. I believe any state ...
1
vote
1answer
306 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 ...
2
votes
0answers
32 views

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 ...
0
votes
0answers
13 views

Modelling reservoir in Qutip

Is there any way to model reservoir in QuTIP? I was trying to simulate a two sided cavity coupled with a reservoir using QuTIP and I can't find out how the reservoir terms in Hamiltonian are added to ...
1
vote
1answer
174 views

Is it possible to demonstrate a quadratic speed-up of a quantum algorithm on a classical computer?

In article Quantum computational finance: Monte Carlo pricing of financial derivatives the authors said that: Firstly: While a practical quantum computer has yet to become a reality, we can ...
2
votes
0answers
48 views

Software for implementing Quantum Machine Learning

I want to have a software product specifically suited for Quantum Machine Learning. Please help me with a list of software product which has been designed specifically for implementing Quantum Machine ...
1
vote
1answer
336 views

How to run the Qiskit Aer simulator without noise?

I know that the Qasm Simulator execute quantum circuits with presence of noise, even if I do not specify the model of noise in options for that backend. But how can I execute the circuits without ...
2
votes
1answer
83 views

Commutation of bosonic operators on finite Hilbert space

I'm checking this article of R. Somma about quantum simulations https://arxiv.org/abs/quant-ph/0512209 I understand the common commutation relations for creationd and annihilation operators, given ...
1
vote
1answer
80 views

What is the difference between IBM quantum simulator and others

I am currently doing my final year undegraduate research. For many quantum inspired algorithms are simulated on Matlab. However if I am to run the algorithms on a Quantum Simulator provided by IBM, ...
8
votes
1answer
635 views

Why are non-Clifford gates more complex than Clifford gates?

There are two groups of quantum gates - Clifford gates and non-Clifford gates. Representatives of Clifford gates are Pauli matrices $I$, $X$, $Y$ and $Z$, Hadamard gate $H$, $S$ gate and $CNOT$ gate. ...
1
vote
1answer
104 views

Strange Behaviour of MeSolve, McSolve

I'm using Qutip to plot some basic two level dynamics using hamiltonians with a temporal envelope defined as the sum of two error functions, designed to make it more representative of experimental ...
2
votes
0answers
168 views

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 ...
2
votes
1answer
136 views

Monty Hall Problem in Quantum Computing [closed]

Is it possible to make a quantum Monty Hall problem where the quantum computer wins the game always?
9
votes
1answer
186 views

Where does precisely the dificulty in exponentiating a Hamiltonian $H$ in the quantum simulation problem lay?

I've read in the Nielsen's, Chuang's "Quantum Computation and Quantum Information": Classical simulation begins with the realization that in solving a simple differential equation such as $dy/dt = ...
1
vote
2answers
136 views

How to generate a SWAP of $N$ qubits?

I know that SWAP2 (swaps 2 qubits) gate looks like: $$ SWAP2=\begin{bmatrix} 1 & 0 & 0 & 0 \\ 0 & 0 & 1 & 0 \\ 0 & 1 & 0 & 0 \\ 0 & 0 & 0 & 1 \end{...
2
votes
1answer
77 views

How do I apply a controlled gate to specific qbits in the register?

Say, I have a specific scheme, where I need to specify inputs for controlled R logical gate, which here is $$ R(\theta)=\begin{bmatrix} 1 & 0 & 0 & 0 \\ 0 & 1 & 0 & 0 \\ 0 &...
3
votes
1answer
148 views

How is the precision of a quantum simulation algorithm actually proved?

The problem of quantum simulation can be formulated as follows: Given a Hamiltonian $H$ ( $2^n \times 2^n$ hermitian matrix acting on $n$ qubits), a time $t$ and maximum simulation error $\epsilon$,...
3
votes
1answer
188 views

In qiskit, doing 2 subsequent measurements of a Hadamard gate on the same qubit always gives 0 on the 2nd one

When I execute the following circuit, I expect that in both classical registers, the content is identical. ...
0
votes
1answer
277 views

Can my MatLab code be used as a good simulator of a quantum computer?

I have tried to program universal quantum computer simulator in MatLab. Please find a code here: https://www.mathworks.com/matlabcentral/fileexchange/73035-quantum-computer-simulator Can be this ...
4
votes
0answers
39 views

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 ...
3
votes
1answer
272 views

How to selectively apply noise in Qiskit simulations?

In Qiskit it is possible to specify noise models to apply to simulations. This allows noise to be defined for certain operations, like measurement or each type of gate. Is it also possible to change ...
1
vote
0answers
97 views

What is the cost of implementing the Quantum Fourier transform in a classical computer?

What is the cost of implementing the Quantum Fourier transform (QFT) in a classical computer? We know we require at least $\log{n}$ depth quantum circuits to do a QFT in a quantum computer, with $n$ ...
1
vote
0answers
18 views

Quantum Simulation Of Tunneling in Small System

how a single Pauli z-gate (on particular qubit) on the highest order qubit realize square well potential? How upon acting same gate on the second highest qubit, realize double square well potential? ...
2
votes
1answer
80 views

Can we simulate quantum many-body systems with IBMQ Experience?

Consider physical systems such as electrons in metals, or Bose-Einstein condensates, or any crystal, which are realised in the real three-dimensional space. If we want to simulate these systems on a ...
2
votes
0answers
150 views

Error ERROR_TRANSPILING_JOB when trying to simulate the circuit

I'm trying to implement an algorithm (https://dl.acm.org/citation.cfm?id=1128034, basically a simple Grover Algorithm in which the oracle is made of a Fitness operator- some CNOT gates- and 2 adders) ...
5
votes
2answers
149 views

Simulating depth-2 circuits

Quantum depth-2 circuits can be efficiently simulated classically, as shown in Proposition 2 of this paper. The following is a quote of the proof. After the first time step the quantum state of the ...
3
votes
1answer
258 views

Reversible Circuit Simulation (for classical tests of quantum subroutines)

Problem: trying to implement and test quantum subroutines on quantum simulators I run into multiple challenges: Quantum simulation is a very hard problem: a very low number of simulated qubits is ...
2
votes
1answer
124 views

Implementing noise model in Quantum simulator

I have noticed that a few papers, such as this one, provide models two for typical noise that a qubit encounters during network transmission: Λ is the dephasing channel Λ(ρ) = Pq(ρ) = qρ + (1 − q)ZρZ ...
7
votes
2answers
2k views

Why doesn't the Gottesman-Knill theorem render quantum computing almost useless?

The Gottesman-Knill theore states (from Nielsen and Chuang) Suppose a quantum computation is performed which involves only the following elements: state preparations in the computational basis, ...
4
votes
3answers
453 views

How to create an Ising coupling gate with Qiskit?

I'm trying to apply a time evolution algorithm for a physical system I'm trying to simulate on QISkit, however, in order to do that, I need to use the so-called Ising coupling gate: $I=\begin{pmatrix}...
7
votes
0answers
81 views

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 ...
1
vote
2answers
211 views

How to get samples in “bins” from D-Wave's dimod?

at 1, the following code example is available: ...
2
votes
2answers
194 views

GridQubit in Cirq vs LineQubit

It's perhaps a very silly question, but in what ways is it advantageous to use GridQubit vs LineQubits to develop quantum circuits? Specially to develop ansatz ? Are GridQubits Cirq's way of ...
4
votes
1answer
243 views

How to implement NM Algorithm for Variational Quantum Eigensolver?

First of all: thanks for reading again. I appreciate the feedback I have gotten from this community the past weeks as I started to feel ready to ask questions about quantum computing topics. I am ...
3
votes
0answers
27 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 ...
4
votes
1answer
480 views

Plotting Bloch sphere in QuTiP

Is there anyone who reproduced the Bloch sphere given in the paper QuTiP: An open-source Python framework for the dynamics of open quantum systems by J. R. Johansson, P. D. Nation, Franco Nori? I am ...
4
votes
0answers
56 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 ...
6
votes
3answers
2k views

Is there any online Bloch sphere simulator?

While writing this answer I realized it would be really helpful if I could show the OP a video or .gif of how qubit states in Bloch spheres transform under certain unitary operations. I googled up a ...
4
votes
0answers
84 views

Simulating quantum computers using anyon braiding

I am new to the concept of topological quantum computation (TQC). Recently I have been thinking about simulating a quantum computer on a classical computer. I know that if I use merely the unitary ...
1
vote
1answer
61 views

Interpreting results from IBM's processor vs. simulator

I am working with a circuit where I use 4 cables, and perform measurements in all of them. Nevertheless, I am only interested in the results from two cables since the other two are ancillas. When I ...
5
votes
2answers
251 views

Why can't a quantum computer strongly simulate itself?

We can strongly simulate a quantum circuit if we can estimate the probability of measuring $|0^n\rangle$, say, at the end to within some fixed relative error. Now, by measurement, a quantum ...
3
votes
0answers
75 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 ...
3
votes
1answer
174 views

For CNOT gate with control qubit set to 1, the measured state of the second qubit unexpectedly depends on the measurement

I have the following circuit in qiskit. It is a simple CNOT operation with the control qubit set to 1, by running the control qubit through an X-gate. However, when I measure the 2nd qubit, I get the ...
4
votes
1answer
61 views

Creating .gifs corresponding to Quirk simulations

Craig Gidney's blog has some .gifs which directly link to the corresponding simulation on Quirk. For example: Grover Search Delayed Eraser Is it possible to create these .gifs from within Quirk? Or ...
4
votes
3answers
321 views

Why is there a difference between the simulation results and the actual quantum computer results?

I ran the Grover's Algorithm for 3 Qubits on the IBM Q platform (ibmqx4) and the results of the simulation and the actual computer differ a lot. The screenshots of the circuit and the results are ...
2
votes
1answer
93 views

ProjectQ - In which part of the controlled gate object are the control bits scored

I've been trying to decompose the ProjectQ objects and I could manage to decompose non-controlled gates and daggered gates. But I noticed that the object of a controlled version of a gate is the ...
5
votes
1answer
118 views

Where does the Xmon simulator from Googles cirq framework its entropy from?

Measurements create entropy as we all know. But computers themselves are deterministic machines. Most devices use processor heat as a source for random number generation as far as I know - which has ...
4
votes
1answer
506 views

How can noise on a device be simulated using measured noise parameters?

The real devices used as backends for Qiskit have calibration data that quantifies errors ($T_1$ and $T_2$, gate fidelities, etc). This can be accessed by, for example ...
5
votes
1answer
192 views

Introspecting quantum circuit execution on Qiskit Aer simulators

Is there any way to get information from intermediate points in the execution of a quantum circuit. This is not possible on real quantum hardware but would be very useful on the Aer simulators for ...