Questions tagged [simulation]
For questions about simulating either quantum computers or simulating things on quantum computers.
4
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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
38 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
71 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
44 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
102 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
66 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
63 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
101 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
46 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
70 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
138 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
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1answer
45 views
Is it possible to see how CompositeGates are decomposed when simulated using XmonSimulator?
I'm simulating a circuit like this:
...
4
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1answer
91 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
184 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
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1answer
79 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
60 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, ...
9
votes
4answers
606 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
55 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
67 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
58 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 ...
4
votes
2answers
80 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
138 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
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2answers
205 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
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2answers
441 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
122 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 ...
5
votes
1answer
106 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
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0answers
77 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 ...
9
votes
2answers
179 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
200 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
189 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
200 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
72 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
285 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 ...
5
votes
3answers
523 views
Is it possible to simulate a quantum computer in Virtual Reality? If yes, how?
There have been a couple of simulations already made and I recently saw this high performance, hardware accelerated quantum computer simulator QCGPU and started to wonder about how to simulate quantum ...
7
votes
2answers
312 views
What do we mean by parity of qubits?
I am currently reading "Quantum Computation and Quantum Information" by Nielsen and Chuang. In the section about Quantum Simulation, they give an illustrative example (section 4.7.3), which I don't ...
10
votes
1answer
278 views
Obtaining gate $e^{-i\Delta t Z}$ from elementary gates
I am currently reading "Quantum Computation and Quantum Information" by Nielsen and Chuang. In the section about Quantum Simulation, they give an illustrative example (section 4.7.3), which I don't ...
9
votes
1answer
102 views
Simulating Clifford + few-T circuits
I want to simulate large stabilizer circuits (H/S/CNOT/MEASURE/feedforward) with a small number of T gates mixed in. How can I do this in a way that scales exponentially only in the number of T gates? ...
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0answers
432 views
Explicit Lieb-Robinson Velocity Bounds
Lieb-Robinson bounds describe how effects are propagated through a system due to a local Hamiltonian. They are often described in the form
$$
\left|[A,B(t)]\right|\leq Ce^{vt-l},
$$
where $A$ and $B$ ...
10
votes
1answer
84 views
Is there any source which tabulates quantum computing algorithms for simulating physical systems?
I was wondering if there is a source (online or review article) which tabulates recent algorithms, and their complexities, used in simulating various physical systems. Something along the lines of:
...
13
votes
3answers
710 views
What would a very simple quantum program look like?
After reading the "first programmable quantum photonic chip". I was wondering just what software for a computer that uses quantum entanglement would be like.
Is there any example of code for specific ...
12
votes
4answers
799 views
Do real commercial quantum computers exist?
We have been reading about quantum computers being developed and tested in labs.
And also, we have quantum simulator programs that use limited virtual qubits (up to 30-40 qubits if cloud-based).
And ...
0
votes
2answers
539 views
Is the universe indistinguishable from a giant quantum computer? [closed]
Seth Lloyd, a professor of mechanical engineering and physics at MIT, published a paper and a book in which he shows that the universe can be
regarded as a giant quantum computer. According to him, ...
7
votes
1answer
134 views
New algorithm for faster QC simulation by IBM
This new algorithm for QC calculation was introduced recently (2017 4Q) by IBM/ Pednault et al. to great fanfare. The paper seems more couched in the language of physics.
Are there any basic ...
13
votes
3answers
275 views
How to compactly represent multiple qubit states?
Since access to quantum devices capable of quantum computing is still extremely limited, it is of interest to simulate quantum computations on a classical computer. Representing the state of $n$ ...
14
votes
3answers
1k views
Building a quantum computer in simulation
If one wants to start building a quantum computer from scratch inside simulations (like how people get to build a classical computer from scratch in the Nand2Tetris course), is it possible?
If yes, ...
0
votes
1answer
391 views
How much memory is required to simulate a 48-qubit circuit?
This CDMTCS Report 514, 2017 entitled "The Road to Quantum Computational Supremacy" states (in Section 6) that the amount of memory needed to simulate random quantum circuits on classical computers ...
26
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2answers
683 views
Can a quantum computer simulate a normal computer?
Similar to the question Could a Turing Machine simulate a quantum computer?: given a 'classical' algorithm, is it always possible to formulate an equivalent algorithm which can be performed on a ...
9
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1answer
151 views
Simulating a system inside a system
The minimum size of a computer that could simulate the universe would
be the universe itself.
This is quite a pretty big theory in classical computing and physics because to contain the information ...
58
votes
3answers
2k views
Can a Turing machine simulate a quantum computer?
I know that a Turing machine1 can theoretically simulate "anything", but I don't know whether it could simulate something as fundamentally different as a quantum-based computer. Are there any ...
