All Questions
39 questions
2
votes
0
answers
78
views
How to simulate a beam splitter in QuTiP?
I'm trying to mix two states on a beam splitter whose unitary operator is
$$\hat{U}=e^{i\theta \left( \hat{a}^†\hat{b} + \hat{a}\hat{b}^† \right)},$$
where $\hat{a}$, $\hat{b}$ are annihilation ...
- 21
1
vote
0
answers
28
views
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 ...
1
vote
1
answer
29
views
Unexpected behavior of trapped ion's motional mode (phonon) heating simulation
I'm a novice at qutip simulation.
I was recently trying to use qutip to simulate the heating effect of a trapped ion by defining a jump operator defined with heating rate.
Below is the code of my ...
- 21
0
votes
0
answers
35
views
Cosine of an operator (a+a.dag()).cosm() in Qutip does not work as it should
As mentioned in the title, the .cosm() method in QuTip fails to give the correct evolution under the Hamiltonian. I am trying to define the Hamiltonian of a non-linear LCJ circuit as follows:
...
- 11
0
votes
0
answers
26
views
Particle number expectation value in QuTip
I am learning now to use QuTiP by going through their documentation site. I am trying to understand what does the argument - particle number expectation value in thermal density matrix do? How does it ...
- 33
3
votes
2
answers
374
views
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 ...
- 121
2
votes
1
answer
274
views
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 ...
- 435
1
vote
0
answers
57
views
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(...
- 125
2
votes
0
answers
55
views
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. ...
- 367
1
vote
1
answer
336
views
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
1
vote
0
answers
39
views
0
votes
1
answer
171
views
QuTip newbie need to understand .reshape()
I am a quantum physics researcher but till now I have been using Mathematica symbolic language for solving quantum problems. I wanted to develop numerical skills as well so I just started to learn ...
- 11
1
vote
0
answers
64
views
How to check the jmat operators on Qutip?
I'm trying to reproduce this Qobject form Qutip
https://qutip.org/docs/latest/guide/guide-tensor.html#a-two-level-system-coupled-to-a-cavity-the-jaynes-cummings-model
but, I'm using the Jmat ...
- 11
1
vote
1
answer
30
views
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?
1
vote
2
answers
507
views
Generating and executing large Pauli rotations in Python
I am interested in generating collective Pauli X, Y and Z spin operators for the purpose of rotating $2^N$ dimensional state vectors $|\psi\rangle$ (in the computational basis) for a quantum protocol. ...
- 921
1
vote
0
answers
177
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 ...
1
vote
1
answer
508
views
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
2
votes
1
answer
197
views
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:
...
- 624
2
votes
0
answers
76
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 ...
- 21
1
vote
1
answer
436
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
0
answers
321
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
0
answers
49
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 ...
- 152
2
votes
1
answer
194
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\...
- 21
5
votes
1
answer
1k
views
Python shorthand for tensor product (Kronecker product)
When using numpy or tensorflow in Python, we can simply write
C = A @ B
for matrix ...
- 171
1
vote
1
answer
513
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 $\...
- 113
4
votes
1
answer
134
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 ...
- 179
2
votes
1
answer
608
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
0
votes
1
answer
409
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-...
- 775
0
votes
1
answer
386
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 ...
- 103
1
vote
0
answers
348
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
2
votes
1
answer
416
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 ...
- 23
1
vote
1
answer
936
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.
...
- 596
3
votes
0
answers
174
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 ...
- 31
2
votes
0
answers
130
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 ...
- 399
3
votes
0
answers
93
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 ...
- 71
4
votes
1
answer
983
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 ...
- 71
2
votes
1
answer
272
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 $\frac{1}{\sqrt{2}}(|0,0\rangle + |1,1\rangle)$:
...
- 123
6
votes
1
answer
796
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 ...
- 253
6
votes
4
answers
2k
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 ...
- 1,567