Questions tagged [qutip]

For questions about code which makes some use of QuTiP (Quantum Toolbox in Python). It is an open-source software library for simulating the dynamics of closed and open quantum systems. Please don't use the programming tag unless you absolutely think it is related to your question. Basically, questions which involve calculating physical quantities, by doing numerical computations on a computer are suited for this tag.

For more about QuTiP best place is Ref.
"The QuTiP library depends on the excellent Numpy, Scipy, and Cython numerical packages. It produces plots using the backends provided by matplotlib. QuTiP aims to provide user-friendly and efficient numerical simulations of a wide variety of quantum mechanical problems, including those with Hamiltonians and/or collapse operators with arbitrary time-dependence, commonly found in a wide range of physics applications. QuTiP is freely available for use and/or modification, and it can be used on all Unix-based platforms and on Windows. Being free of any licensing fees, QuTiP is ideal for exploring quantum mechanics in research as well as in the classroom." This tag is not related to writing programs (or any related software like qiskit) which can be run on a quantum computer. In fact these programs would most probably be written in python.

67 questions
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Is the analytical solution right?

This question requires the knowledge of GRAPE. More info can be found here and in this short presentation. In the following jupyter notebook is the analytical solution as in this image right? Because on trying (g = pi/ 4* T = 1/8) as in this figure…
Tejas Shetty
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What is the need of convolution here?

This jupyter notebook implements GRAPE for the synthesisizing a CNOT gate. More info can be found here and in this short presentation. In the following jupyter notebook at In[8] 1 the starting guess for the control field is prepared as…
Tejas Shetty
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Effective Hamiltonian using Schrieffer-Wolff transformation and QuTiP

I would like to study the effects of non-computational levels of two coupled qubits by a resonator using QuTiP. The idea is to consider the following Hamiltonians Qubits Hamiltonian $$ H_{q_i} = \sum_n 4E_C (n-n_g)^2|n\rangle\langle n| +…
Frostman
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Why does qutip run without errors, but cannot output a Bloch sphere graph?

This is the official demo(https://nbviewer.ipython.org/github/qutip/qutip-notebooks/blob/master/examples/visualization-exposition.ipynb). But after I run it, there is no error, but I can't output the graph of the Bloch sphere. This does not match…
Ren-Xin Zhao
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Different values of similar functions

This question requires the knowledge of GRAPE. More info can be found here and in this short presentation. In the following jupyter notebook the result of this line _overlap(result.U_f, U_f_numerical).real, abs(_overlap(result.U_f,…
Tejas Shetty
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lindblad_dissipator function appears to use unconventional convention

In the QUTIP documentation for the lindblad_dissipator(a,b) function we see that some of the $a$'s have daggers and others do not (link to documentation…
Dast
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Calculate an Qobjevo operator of qutip

I define a time-dependent operator in the form of an Qobjevo and pass it to sesolve() to solve for Schrodinger's equation. Below is an MWE. from qutip import * import numpy as np tlist = np.linspace(0, np.pi / 2) H = [ sigmaz(), [sigmax(),…
Neo
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How to read random quantum channels with QuTiP

This is somewhat a simple question. If we generate random channels using QuTiP, say that we generate a channel that acts on a 3-dim space using rand_super_bcsz(3) we get the following output as an instance, Quantum object: dims = [[[3], [3]], [[3],…
R.W
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What does the parameter "targets" in gates stand for in QuTiP?

As far as I understand, "targets" is a basis (of the qubits system) to which gate is applied. For instance, Hadamard gate takes basis of a single qubit system, and CNOT gate takes a basis vector of a 2-qubit system. However, it is possible to enter…
levgor
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Qutip mesolve gives different results depending on number of points in time list

I get different results from mesolve when I change the number points in tlist. The Hamiltonian and initial vector are the same. The results from mesolve are also incorrect (however, essolve gives me the correct answer from any number of points in…
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Acting with a superoperator to states in qutip

I can generate a random superoperator in qutip using the command rand_super(N) $\mathcal{E}$ where I only need to inser the dimension of the superoperator is acting on, denoted as N. The same superoperator should be able to act on a state, that is a…
R.W
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Erroneous position squared expectation value with Fock states in qutip

Trying the following code in qutip rho = basis(6, 5) * basis(6, 5).dag() x = (create(6) + destroy(6)) / np.sqrt(2) Now, expect(x, rho) gives the expected answer 0. But when I try expect(x * x, rho) I get 2.4999999999999996, instead of the expected…
sbp
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