# 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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### Use qiskit calibration data for noisy simulation in Qutip

Is it possible to illustrate an example code in which a quantum circuit is taken as an input and the qiskit backend properties are feed to a custom compiler to perform noisy simulation using QuTip? ...
• 181
1 vote
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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 ...
• 11
1 vote
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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 ...
113 views

### How do I stepwise rotate a qubit on a Bloch sphere using $SO(3)$ and $SU(2)$ group?

Let us first introduce two fundamental functions for coordinate transformations: ...
1 vote
64 views

### 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 ...
31 views

### qutip.sesolve and qutip.optimize_pulse_unitary produce different results

I'm currently trying out some things with qutip in the field of optimal control (state-to-state transfer) and have some trouble to reproduce my results from the optimization process with sesolve. My ...
• 21
1 vote
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### QuTIP tensor products

I am referring to the QuTIP package https://qutip.org/ To describe a system of 3 atoms in the ground state, I can crate the wavefunction: tensor( basis(2,0), basis(2,0), basis(2,0) ) Now suppose that ...
• 13
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### The result from process matrix to kraus operators and kraus operators to process matrix is not same QUTIP

Here is my process matrix: ...
• 426
1 vote
73 views

### 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 ...
• 1,391
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### Qutip choi_to_kraus and to_kraus functions are not returning list of Kraus representation

I am trying to find my kraus representation from my process matrix. Suppose that, I have these process matrix: ...
• 426
1 vote
23 views

### QuTip - Is there a way to simulate more than one inital state in one simulation?

I'm trying to use QuTip for a simulation of a qutrit system and I want to see how my system evolves under different initial states. Is there a way to do it using QuTip without running the simulation ...
1 vote
123 views

### QuTip: How to multiply symbol with matrix

I am trying to multiply a symbol with a matrix which is defined by QuTip quantum object, but I got this error: TypeError: Incompatible object for multiplication I ...
1 vote
77 views

### QuTiP VS RK45: Which one gives the correct results for time-dependent systems?

I am writing a code for a quantum thermal machine which includes both coherent and dissipative time evolutions in its different stages of operation. However, evolving the system with "mesolve&...
• 111
1 vote
34 views

### 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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### 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 ...
164 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 ...
• 79
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### 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-...
• 647
146 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 ...
136 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 ...
• 647
1 vote
149 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 ...
• 11
208 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 ...
1 vote
663 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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### 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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1 vote
41 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 ...
• 349
1 vote
48 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, ...
• 349
1 vote
45 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 ...
• 349
89 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 ...
• 349
73 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 ...
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647 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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171 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 $\frac{1}{\sqrt{2}}(|0,0\rangle + |1,1\rangle)$: ...
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544 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 ...
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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 ...