Questions tagged [simulation]
For questions about simulating either quantum computers or simulating things on quantum computers.
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questions
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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
55 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
34 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
...
5
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, ...
3
votes
3answers
48 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}...
6
votes
0answers
42 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
36 views
How to get samples in “bins” from D-Wave's dimod?
at 1, the following code example is available:
...
1
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2answers
35 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
91 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
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0answers
23 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 ...
0
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0answers
40 views
Illustrating limitations of quantum computing
Can you illustrate why even with a functioning quantum computing energy minimization in an Ising Model simulation, an NP-hard problem, cannot be solved?
3
votes
1answer
42 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
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0answers
41 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 ...
5
votes
2answers
194 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
50 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
42 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 ...
4
votes
2answers
195 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
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0answers
53 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
92 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
48 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
187 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
77 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
82 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
191 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
...
2
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0answers
57 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 ...
4
votes
1answer
83 views
Numerical quantum state tomography simulator
On a classical computer, I want to simulate a learning-based quantum state tomography of a qubit. We can formulate it as finding a parametrized unitary evolution that takes the unknown pure state to a ...
2
votes
2answers
154 views
Are there emulators for quantum networks?
Inspired by the question Are there emulators for quantum computers?, I'm curious to know if it's possible to emulate a quantum network on a classic computer. Additionally, is it possible to emulate a ...
2
votes
1answer
55 views
Is it possible to see how CompositeGates are decomposed when simulated using XmonSimulator?
I'm simulating a circuit like this:
...
4
votes
1answer
118 views
Unitary gate(s) from product of exponent
Often unitary gates are defined as a product of exponentials, with some parameter in the power-term. However, often it is not clear how to construct unitary gates from it, at least not for me that is. ...
0
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0answers
291 views
FPGA qubit simulation
This question is regarding the simulation of qubits, using FPGAs. My question is: how does using FPGAs to simulate qubits help us understand or give us an insight into how quantum computers could be ...
2
votes
1answer
87 views
List of known circuits and their expected output
I've written an API which takes in a circuit scaffold, according to some specifications, and outputs the results of simulating the circuit. The circuit constraints are that the measurements are ...
3
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0answers
66 views
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, ...
10
votes
5answers
1k views
How would I implement the quantum oracle in Deutsch's algorithm?
I am trying to simulate Deutsch's algorithm (elementary case of Deutsch-Josza algorithm), and I am not entirely sure how I would go about implementing the quantum oracle necessary for the algorithm to ...
3
votes
1answer
62 views
Could we use varying voltage with programmable gates?
One of the benefits I'm reading about qubits is that they can be in an infinite number of states. I'm aware of Holevo's bound (even though I don't fully understand it). However, it made me think of ...
2
votes
1answer
92 views
How to simulate quantum entanglement variation in different quantum gates?
I'm trying to study quantum entanglement variation during quantum computation with 4 qubit systems comprising a variety of quantum gates.
How can I simulate this variation on MATLAB? Is there any ...
5
votes
1answer
96 views
Which QC platform is better to use on HPC cluster?
I have a HPC (High Performance Computing) cluster with NVIDIA GPU and Xeon CPU partitions.
Is this simulator list complete?
Which do you recommended to use on a HPC cluster?
Will it increase the ...
7
votes
2answers
104 views
How does one obtain amplitude information in Q#?
Is it possible to obtain amplitude information (in lexicographic ordering) for a particular qubit register in Q#?
For example, in the following code:
...
10
votes
2answers
2k views
Classical Memory enough to store states up to 40 qubits quantum system?
As a part of a discussion with my 'classical' friend, he insisted that making a a state machine for calculating the outcome of quantum computer is possible; so, simply calculate the outcomes of (known)...
4
votes
2answers
190 views
Finding the maximum number of Q# simulatable qubits
I'm new to Q# and I was curious on how one would find the number of Q# simulatable qubits for a specific machine. I know Microsoft has an approximation of 16GB ~ 30 qubits but I wanted a better ...
6
votes
2answers
229 views
Are quantum simulators like Microsoft Q# actually using quantum mechanics in their chips?
Unlike Google's Bristlecone or IBM's Qbit computer, do simulators like Q# or Alibaba really use quantum mechanics anywhere in their physical chips? Are they just defining properties using a classical ...
6
votes
2answers
471 views
Incorrectly Calculating Probability Amplitudes for 3-qbit Circuit
I’m trying to calculate the probability amplitudes for this circuit:
My Octave code is:
...
8
votes
2answers
136 views
Can we perform quantum mechanical simulations using a quantum computer?
I'm a computer science major who's really keen on physics and quantum mechanics. I have started learning about Q# and D-Wave, but I just wanted to know if it's possible to test quantum mechanical ...
6
votes
1answer
112 views
What are the preferred numerical methods to simulate the evolution of a state through a time-dependent Hamiltonian?
Under the influence of a time-independent Hamiltonian $H$, a state $|\psi\rangle$ will evolve after a time $t$ to the final state $|\psi(t)\rangle=e^{-iH t}|\psi\rangle$, while in the most general ...
5
votes
0answers
80 views
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 ...
10
votes
2answers
198 views
Hamiltonian simulation with complex coefficients
As part of a variational algorithm, I would like to construct a quantum circuit (ideally with pyQuil) that simulates a Hamiltonian of the form:
$H = 0.3 \cdot Z_3Z_4 + 0.12\cdot Z_1Z_3 + [...] +
- ...
4
votes
2answers
256 views
How many qubits are simulable with a normal computer and freely accessible simulators?
I want to simulate an arbitrary isolated quantum circuit acting on $n$ qubits (i.e. a pure state of $n$ qubits).
As I know RAM is the bottleneck for quantum simulators, you can consider a "normal" ...
6
votes
2answers
212 views
What are some good quantum computing simulator and visualiser? [duplicate]
I am looking for some good software to simulate quantum computing, visually if possible.
I know about quirk (http://algassert.com/quirk)
and IBM Q Experience (https://quantumexperience.ng.bluemix....
5
votes
0answers
255 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 ...
8
votes
1answer
80 views
Why does (almost) every pair of Hamiltonians generate, through repeated commutation, the whole space of Hermitian matrices?
In [1], the problem of simulating a Hamiltonian using repeated applications of a different set of Hamiltonians is discussed.
In particular, let $A$ and $B$ be a pair of Hermitian operators, and let $\...
14
votes
1answer
372 views
Hamiltonian simulation is BQP-complete
Many papers assert that Hamiltonian simulation is BQP-complete
(e.g.,
Hamiltonian simulation with nearly optimal dependence on all parameters and Hamiltonian Simulation by Qubitization).
It is easy ...
