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.
79 questions
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Converting numpy array representing Choi matrix to Kraus operators in QuTip
I want to convert a Choi matrix into a corresponding set of Kraus operators.
I start out from a numpy array representing the Choi matrix. I convert it to a QuTip Qobj object and then convert it to ...
- 53
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Retriving information from a circuit with Qutrits in pure states
The problem I am facing is that I have a circuit of n qutrit all starting in a pure state, after the application of some gates (that keeps states pure), my system will have a final state in the form ...
- 49
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Hahn Echo in a qubit decoherence simulation giving a T_2^{echo } too short
I made a qubit simulation in qutip with dephasing and relaxation for a project but there's a problem in my t2 hahn echo simulation. The time I am obtaining is too short compared to the T2 parameter. ...
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Unintended "decoherence" when evolving a three level system using qutip.mesolve
I am trying to simulate the evolution of a three-level system, using mesolve.
Strangely, the state seems to "decohere" without any collapse operators involved.
At the moment, I am just ...
- 11
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Is mcsolve from QuTiP Optimal for Solving Large Systems in the Lindblad Master Equation?
I am transitioning from using Mathematica to Python for my work on quantum systems, specifically focusing on solving the Lindblad Master Equation. For this purpose, I've started using the mcsolve ...
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QuTiP tutorial: How to derive the analytical solution to the expectation value of an operator for a system evolving by Lindbladian
I am following the simple tutorial below:
(https://nbviewer.org/urls/qutip.org/qutip-tutorials/tutorials-v5/time-evolution/003_qubit-dynamics.ipynb)
In this they look at single qubit with Hamiltonian $...
2
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2
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478
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Python package for quantum computations based on symbolic variables
I am searching for a quantum package in Python that can enable me to calculate, for example, a density matrix symbolically and display the results in variable form rather than numerically. I am aware ...
- 131
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476
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QuTiP ptrace function results do not recreate original composite system
I have a qutip density matrix fullsystem for a system composed of two quantum systems with ...
- 455
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Zeeman eigenstates and QuTiP Bloch sphere
One Hamiltonian corresponding to a qubit is the Zeeman Hamiltonian:
$$
\hat{H}_\mathrm{Zeeman} = \frac{\hbar\omega_0}{2}\hat{\sigma_z}$$
The eigenstate corresponding to the eigenvaue $+\hbar\omega_0/2$...
- 111
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How to use parameters in QuTiP?
I am working with QuTiP to do some calculations based on my proposed Hamiltonian. The Hamiltonian of my system has some coupling constants that show the strength of coupling between matter and light(...
- 117
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Is there a Qutip equivalent of "expand_operator" for superoperators?
I want to calculate a superoperator for a small noisy subsystem consisting of $k$ qubits, and expand it to $n > k$ qubits, where the remaining $n-k$ qubits are not subject to any noise. ...
- 442
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270
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Density matrix and State vector give different result in mesolve in QuTiP
qutip mesolve gives me different population evolve depending on that initial state is state vector or density matrix. And, in some situation, it gives me negative population. It doesn't make sense...
...
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474
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Eigenstates differ between Qutip and Quspin
I am currently trying to adapt a code working well with Qutip to Quspin to optimize it.
I managed to create what I believe are the same systems with both libraries, but I don't get the same ...
- 131
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49
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100
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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 https://...
- 121
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Operating Hamiltonian on discrete variable state [closed]
I have a hamiltonian consisting of combinations of a and a(dragger). i need to act this on discrete variable state like |0,0,0,1> and so on. Is there any library to do these kinds of operations?
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GRAPE with Python?
I want to do some quick GRAPE calculations in Python. The qutip implementation is handy but I can't modify the fidelity function. However, I need to use my own fidelity function to evaluate fidelity. ...
- 327
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Can superoperators work in Monte Carlo solver in QuTip?
The Monte Carlo solver works with kets instead of density matrices. And it doesn't allow a superoperator (which acts on density matrices or superkets) as a collapse operator. Since my master equation ...
- 313
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130
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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, ...
- 113
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171
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QuTiP, Continuous variable systems: Calculating the expectation value of an operator from the covariance matrix
Let's say I have the covariance matrix for a 4-mode system, $\sigma$, which is an $8 \times 8 $ matrix (the first moments are zero). I want to calculate the expectation value for an operator, for ...
- 337
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How to compute projective probabilities of a given measurement outcome using Stim?
I am looking to calculate the projective probabilities for each measurement outcome in a Clifford circuit and then output its corresponding tableau state. I am performing the measurement in the Z ...
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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) ...
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How to calculate Quantum Discord for two qubit system using Qutip?
Quantum discord of a bipartite system can be determined as:
$${D_A}({\rho _{AB}}) = I({\rho _{AB}}) - {J_A}({\rho _{AB}}),$$
The subscript of $A$ denotes that the measurement has been performed on the ...
- 141
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How do I implement $SU(2)$ rotation on the Bloch Sphere unsing qutip?
Using qutip I am trying to implement a qubit rotation according the formula $(25)$ provided in this document "Lecture notes: Qubit representations and ...
- 298
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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 ...
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