Questions tagged [simulation]

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

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1answer
103 views

Monty Hall Problem in Quantum Computing

Is it possible to make a quantum Monty Hall problem where the quantum computer wins the game always?
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1answer
254 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 ...
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2answers
111 views

Why should we use density matrices to simulate quantum systems with noise?

Why we should use density matrices to simulate quantum systems with noise? I found that the any QEC circuit is included by some quantum gates just like normal cases, which means the state vector can ...
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3answers
2k 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 ...
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3answers
4k 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 ...
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1answer
31 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 ...
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1answer
42 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 ...
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0answers
24 views

Qiskit density_matrix simulator and memory_profiler

I use jupyter notebook to simulate quantum dummpy code with 'density_matrix' method. Following is my code. Now, I want to check memory usage of it. So I use %memit operation to each functions. ...
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1answer
42 views

Why running time of qasm simulator is significantly smaller in comparison with quantum machines?

I ran a 3-qubit measurement circuit on QASM simulator as well as on IBM Q Melbourne, Santiago and Vigo machines. The running time on the simulator is in few milliseconds (400-800) while in the case of ...
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2answers
33 views

How to plot histogram using statevector simulator?

I'm trying to run my quantum circuit and plot the simulation result (counts) using the statevector simulator (to avoid 'shot noise'). However, instead of a 2-d histogram, the examples on Qiskit ...
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1answer
581 views

What are examples of Hamiltonian simulation problems that are 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 ...
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1answer
37 views

How can I print out the probability of a certain state in histogram?

This is a simulation I did in my program. I'm hoping to print out the probability of the state |0001> (which is 0.052), and store this number in a letter (a). How can I do this? Thanks!!
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2answers
25 views

How to fix “QiskitChemistryError:PySCF is not installed”

I’m trying to simulate LiH using VQE. But I keep getting the error QiskitChemistryError:PySCF is not installed And I tried several ways to see whether my driver for the molecule was typed wrong. But ...
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1answer
24 views

Unable to retrieve result for Job Error during VQE simulation

I am attempting to run a VQE calculation on the 'ibmq_qasm_simulator'. The job is failing with a series of errors caused by: ...
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1answer
20 views

Any good resources for learning about quantum networks and how to do a simulation of BB84 protocol?

I'm a communication engineering student. And I'm thinking of doing my project on BB84 protocol but I don't know where to start. As a beginner, are there any documents or tutorials about quantum ...
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0answers
22 views

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 ...
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1answer
67 views

Is it a good idea to publish a research paper about the simulation of BB84 protocol?

I'm an engineering student. As my end of year project I've simulated BB84 protocol using simulaqron(python). I'm thinking about publishing a paper about this simulation. I haven't published any ...
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1answer
83 views

Preparing any superposition of fixed Hamming weight states

There exists a nice way of preparing any superposition (with real amplitudes — this is the case I'm interested in) of states $\{\ldots0001\rangle,\,|\ldots0010\rangle,\,|\ldots0100\rangle,\ldots\}$, ...
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2answers
94 views

How to run an approximate simulation, and why

I'm looking at the Qiskit getting started documentation, https://qiskit.org/documentation/getting_started.html. They create a quantum circuit and run an approximate simulation on it 1000 times: Why ...
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1answer
48 views

Resource recommendation on quantum simulations

I would like to know more about quantum simulations, so as to start on a few standard physical models (maybe particle in a box, harmonic oscillator, etc.) and then build up on more complex things. But ...
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1answer
50 views

IBMQ_Melbourne Readout error

I am trying to simulate an experiment on IBM's melbourne quantum computer and here are the results Qasm simulator : ibmq_16_melbourne: error why is there such high probability of unwanted states i....
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2answers
147 views

Entanglement Swapping Circuit

I implemented 2 versions of the entanglement swapping circuit in IBM Q. One is using classical measurement to control X, Z gates. Another is just us C-NOT and Controlled-Z. They should be equivalent. ...
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1answer
515 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. ...
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1answer
102 views

How the simulator work?

Recently I focused on how to simulate in classical computer, and I found Qiskit offers qasmsimulator and statevector simulator. ...
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1answer
60 views

A question about how does the single qubit gate simulated in simulator?

I have found the procedure of simulation process as this picture : Image reference. So in the low-level compilers, all single-qubit gates are approximated by the universal gate set (CNOT, H, T, S). ...
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1answer
29 views

What would be the difference between using qsharp library on python vs learning the Q# langauge?

One difference of course is the syntax. But I'm guessing the idea is eventually quantum computers will be able run Q#, whereas now it uses simulations. Will code written in Python with the qSharp ...
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2answers
72 views

Why do I get positive amplitudes when I create a qiskit StateVectorCircuit from only negative amplitudes?

I am using amplitude encoding to encode my features in a quantum circuit. With this I expect to encode e.g. 32 features in five qubits. For the encoding I use qiskit's ...
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2answers
187 views

How does a classical computer simulate nonclassical correlations?

This may be a dumb question, if so please forgive me, it is late at night. I have learned that a classical computer can simulate a quantum computer in exponential time and space, but classical ...
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1answer
36 views

A question about how to emulate quantum states and computation on classical computer

I have understood the concept of "universal quantum gates" in real quantum computer, and the quantum gates and states can be emulated as matrix in classical computer, and the matrix operation can be ...
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0answers
30 views

How to turn off multiprocessing in TensorFlow Quantum

Some background: I'm currently running the same training algorithm with a classical neural network and a quantum circuit, respectively. The NN is implemented in Keras with a TensorFlow backend, the ...
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1answer
131 views

What are the biggest obstacles currently preventing us from solving real world problems defined in terms of quantum simulation?

Quantum simulation (also referred to as Hamiltonian simulation) is defined as follows: In the Hamiltonian simulation problem, given a Hamiltonian $H$ ($2^n \times 2^n$ hermitian matrix acting on $n$...
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0answers
110 views

What is the usefulness of the Suzuki-Trotter formula?

I can't seem to wrap my head around the suzuki-trotter formula. I have seen This answer but I am still confused of the applicability of the formula. Let me explain: As I understand it Trotterization ...
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1answer
97 views

Problem with building quantum circuit for Hamiltonian operation

In the book, Nielsen and Chuang, there is a section on quantum simulation of the quantum search algorithm. Hamiltonion operator is defined as follows- $$ H = |x\rangle\langle x| + |\psi\rangle\langle\...
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1answer
246 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 ...
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1answer
266 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. ...
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23 views

Can We Currently Import Quantum Datasets (Datasets Containing Quantum Data) Onto NISQ-era Quantum Computers?

I'm still investigating the TFQ whitepaper. In one section of the paper, the authors say this with respect to Quantum Datasets In general, [a quantum dataset] might come from a given black-box ...
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5answers
155 views

Does a classical computer really require $2^n$ complex numbers to represent the state of $n$ qubit quantum computer?

One often reads that the key reason why classical computers (probabilistic or deterministic) are unable to simulate quantum algorithms such as Simon's or Shor's efficiently is that a classical ...
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1answer
82 views

Question Regarding Simulating Hamiltonian With Quantum Circuit

There have been a few other questions about this section of Nielsen and Chuang, but when working through the output of the circuit, there are some inconsistencies that are probably due to some mistep/...
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1answer
101 views

What did exactly Google do in simulating a random quantum circuit on a classical computer in supremacy experiment?

I've been working on Google quantum supremacy paper for quite some time now and I have a problem in understanding how exactly they simulate their actual random quantum circuit on a classical computer. ...
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1answer
44 views

Results of SAT on the Qiskit simulator

I computed SAT formula with the Grover search algorithm on the Qiskit simulator with default parameters, but I don't understand why the incorrect solutions don't have a probability of 0? The SAT ...
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2answers
121 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 $P_{00} = |\alpha|^2$...
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1answer
52 views

A question about quantum circuit simulation on PC

In classical logic circuit consisting of AND, OR and others, common gates can be realized by electrnic signal. Each time cycle can run a function unit like the picture below. Now I have read many ...
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2answers
908 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 ...
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2answers
51 views

Ansatz state for finding the lowest eigenvalue of a $2^n\times 2^n$ real matrix using VQE

I would like to find the lowest eigenvalue of a $2^n\times 2^n$ real matrix $H$ using the VQE procedure. The measurement part is simple — I just expand $H$ in a sum of all possible $n$-qubit Pauli ...
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1answer
222 views

How Mature is the Tensorflow Quantum Library [closed]

Where does The Tensorflow Quantum ( TFQ ) library fall on it's maturity curve. In other words can we currently leverage the TFQ ...
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0answers
56 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 ...
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3answers
122 views

Does Planck's constant have any role in quantum computing?

I am new to the area of quantum computing, but as I study it I can't help wonder about the role of the Planck's constant. When one studies quantum mechanics one often finds statements that quantum ...
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1answer
40 views

Rotation of multi-body interaction in quantum circuit

In quantum circuit, how do you implement the rotation of multi-body interaction, such as $e^{-i\theta\sigma_z^1\sigma_z^2\sigma_z^3}$? I already know the case of less than two-body interaction, but I ...
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0answers
25 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 ...
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0answers
41 views

Why Alice and Bob don't get the same result when they measure in the same basis?

I'm simulating the BB84 protocol using simulaqron. My problem is that when Alice and Bob measure in the same basis, they don't get the same result. How can I fix this error? . BB84.py ...