Questions tagged [simulation]

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

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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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24 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 ...
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2answers
50 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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33 views

“$W_n$ state” in Bravyi-Kitaev encoding

For a particular simulation, I need the initial (physical) state of the QC to represent the equal superposition of all single-occupancy fermionic second-quantized states. In Jordan-Wigner encoding, I ...
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1answer
32 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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2answers
33 views

Normalization of the quantum state in Cirq

My understanding, for instance from [1], is the following: Assuming a state $\psi = \alpha |0> + \beta |1>$, where $\alpha$ and $\beta$ can be complex. I believe any state is always normalized, ...
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1answer
68 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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79 views

As part of genomic epidemiology, using 2-Qubit Grover Search Algorithm to track and predict the target state of covid-19 mutation

As part of genomic epidemiology, using my 2-qubit device, I like to apply Grover search algorithm to track and to predict the target state of covid-19 mutation. Specifically, through amplitude ...
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26 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 ...
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12 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 ...
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1answer
110 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 ...
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40 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 ...
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1answer
180 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 ...
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1answer
50 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 ...
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1answer
52 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, ...
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118 views

Why Non-Clifford gates are 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
37 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 ...
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71 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 ...
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1answer
74 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
117 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 = ...
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2answers
77 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{...
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1answer
63 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 &...
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1answer
137 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 $\epsilon$,...
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1answer
166 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. ...
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1answer
162 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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38 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 ...
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1answer
146 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 ...
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77 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 $n$ ...
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15 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? ...
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1answer
75 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 ...
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136 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) ...
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2answers
140 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 ...
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1answer
160 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 ...
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1answer
81 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 ...
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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, ...
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3answers
222 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}...
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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 ...
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2answers
169 views

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

at 1, the following code example is available: ...
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2answers
109 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 ...
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1answer
172 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 ...
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25 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 ...
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52 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?
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1answer
301 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 ...
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47 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 ...
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3answers
1k 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 ...
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71 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 ...
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1answer
54 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 ...
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2answers
222 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 ...
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67 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 ...
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1answer
140 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 ...