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.

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How can extract reduced dynamics of a bipartite system from unitary evolution in quite

Let us assume that I have a bipartite system $A\otimes B$ and an initial product state undergoing some evolution $H^{AB} = H^A+H^B+V^{AB}$, which is time independent. I want to simulate the reduced ...
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1answer
31 views

How to solve non-"cross-damping off" Linblad equation in QuTiP?

As I understand from the official QuTiP guidlines, it is only capable of solving "cross-damping off" Master Equation in form: $\dot{\rho(t)} = -\dfrac{i}{\hbar}[H(t),\rho(t)] + \sum\limits_n\...
2
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1answer
79 views

Python shorthand for tensor product (Kronecker product)

When using numpy or tensorflow in Python, we can simply write C = A @ B for matrix ...
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1answer
40 views

Writing the Jaynes-Cumming model in QuTip

I want to write the Jaynes-Cumming Hamiltonian in QuTip. $$H = \hbar \omega_{C} a^\dagger a + \frac12 \hbar \omega_{a} \sigma_{z} + \hbar \lambda (\sigma_{+} a + \sigma_{-} a^\dagger)$$ I assume $\...
4
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1answer
60 views

Trying to simulate Weak Value Amplification using QuTiP

Weak Value Amplification is a procedure in which one consider a bipartite Hamiltonian of the form $H = g A \otimes B$, where $A$ is called system, $B$ is called meter and $g$ is the extremely small ...
2
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1answer
84 views

Defining dimension of an operator in qutip

My main question: Can someone please explain to me how the list of array is used to define the dimension in qutip? Context: If I have my density operator ...
-1
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1answer
98 views

Find orthogonal state for random 7 qubit state

I have a system that generates a random 7 qubit state and I need a method to always find the orthogonal state. I'm currently using python and qutip for this, representing this 7 qubit state by a 128-...
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1answer
101 views

Using entropy_mutual function in QuTiP

I am trying to calculate mutual entropies using QuTiP, but I am being unsuccessful so far. More specifically, I consider a 2^n x 2^n matrix representing the density operator of a n-qubit bipartite ...
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2answers
91 views

Is there quantum error correction code package for python

I'm working on the development of a new quantum error correction protocol that tries to maximize the coherence of the qubit. Is there a package for python, similar to qutip, that could help me in this ...
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0answers
92 views

Numerical methods for finding an eigen basis of a degenerate Liouvillian

I'm trying to find the steady-state of a master equation, $$\dot{\rho}(t) = \mathcal{L}\rho(t),\tag{1}\label{1}$$ In the form where we vectorise the density matrix and matrixify (??) the Liouvillian ...
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1answer
165 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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1answer
520 views

Can't plot points on the Bloch sphere (QuTip)

I have the really odd problem when it comes to plotting Bloch spheres using QuTip. Plotting state vectors works perfectly fine e.g. ...
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0answers
74 views

How to define initial state $\rvert \Psi(0) \rangle \equiv \rvert 1, -1 \rangle \otimes \rvert 0 \rangle_{\text{cav}} $ of a system in QuTiP?

Say, we have a $\require{mhchem}\ce{^87Rb}$ atom having an electric dipole transition on the $D_{1}$ line and we have two hyperfine ground states, one on $F = 1$ and one on $F = 2$ level. So, we take ...
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0answers
40 views

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 ...
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0answers
39 views

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, ...
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0answers
44 views

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 ...
2
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0answers
83 views

Modifying GRAPE for open quantum systems

This question requires the knowledge of GRAPE. More info can be found here and in this short presentation. I have tried to modify the grape_unitary() function in grape.py also to accommodate open ...
3
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0answers
61 views

How to add states on the Bloch sphere from a master equation?

Can you please help me to find an answer to this question: I am using qutip for the study of quantum systems. suppose I have calculated the solution of the master equation using the ...
4
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1answer
571 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 ...
2
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1answer
149 views

How to prepare a statistical mixture of $|0,0\rangle $ and $ |1,1\rangle $ in QuTiP?

A QuTiP novice here. It's easy to prepare a pure state in QuTiP. For example, to prepare $\frac{1}{\sqrt{2}}(|0,0\rangle + |1,1\rangle)$: ...
6
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1answer
455 views

Drawing tangent vectors to the Bloch sphere with qutip

I need to plot drawings of qubit dynamics on the Bloch sphere. I know QuTip allows to do such drawings but I specifically need to represent evolution velocities on the Bloch sphere so I need to draw ...
6
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4answers
1k views

Measuring qubits in QuTiP

How can you measure qubits in QuTiP? As far as I have seen you can define a Hamiltonian and let it evolve in time. It is also possible to define a quantum circuit, however, measuring and running it ...
4
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0answers
282 views

Computing Majorana "Stars"

I'm trying to implement Majorana's "stellar representation" of a spin-$j$ system as $2j$ points on the $2$-sphere in python. Consulting papers including Extremal quantum states and their Majorana ...