Questions tagged [simulation]

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

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32
votes
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 ...
66
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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 ...
15
votes
5answers
3k 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 ...
13
votes
3answers
5k 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, ...
15
votes
1answer
620 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 ...
15
votes
3answers
541 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 $n$ ...
5
votes
3answers
937 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 ...
16
votes
1answer
578 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 ...
5
votes
0answers
351 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 ...
3
votes
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\...
1
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1answer
247 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 ...
12
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2answers
296 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 + [...] + - ...
7
votes
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 $\{\ldots0001\rangle,\,|\ldots0010\rangle,\,|\ldots0100\rangle,\ldots\}$, ...
5
votes
2answers
395 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" ...
3
votes
1answer
231 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 ...
10
votes
1answer
126 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: ...
7
votes
2answers
149 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: ...
4
votes
1answer
486 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 ...
1
vote
1answer
285 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 ...