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.
55
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QuTip for time-dependent driven harmonic oscillator without damping?
Is it possible to find the dynamics of a time-dependent system? For example, a harmonic oscillator that is driven by an external time-dependent drive? Does QuTip have a way to solve the Schrodinger ...
- 3
0
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1
answer
21
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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 ...
- 3
0
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0
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8
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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://...
- 111
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15
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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 ...
- 1
1
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1
answer
25
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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?
2
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1
answer
67
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Simulate dual Lindblad master equations in the Heisenberg picture in QuTiP
In QuTiP, it is possible to solve Lindblad master equations describing the time evolution of an open quantum system $\rho$:
$$
\dot{\rho}(t)=-\frac{i}{\hbar}[H(t), \rho(t)]+\sum_n \frac{1}{2}\left[2 ...
- 179
1
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1
answer
54
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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. ...
- 167
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39
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How to implement the Mach Zehnder Interferometer in Qutip?
I was trying to implement the Mach-Zehnder Interferometer with a phase shifter in Qutip but I couldn't nail it. I just want to give two number states as input and at the end see the probability ...
1
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1
answer
30
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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 ...
- 131
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2
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102
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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. ...
- 747
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11
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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
1
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0
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34
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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 ...
- 161
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0
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57
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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 ...
- 292
0
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1
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40
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Invert colors in qutip plot_wigner function
In QuTiP, it is possible to plot Wigner functions with positive (shown in blue) and negative (shown in red) values.
For example, the following code displays the Wigner function of a Schrodinger cat ...
- 179
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1
answer
111
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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 ...
- 15
1
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0
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109
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Qutip: Mesolve gives different and weird results with different fock state numbers
I have been trying to simulate the average number of particles at 3 sites of coupled harmonic oscillators.
I have used the code from the below tutorial:
https://notebook.community/ajgpitch/qutip-...
- 11
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0
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31
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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) ...
- 2,247
2
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1
answer
207
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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 ...
- 390
3
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0
answers
94
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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 ...
- 131
0
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0
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61
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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?
...
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1
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1
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57
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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
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1
answer
205
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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 ...
- 278
2
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1
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311
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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:
...
- 278
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1
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206
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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 ...
- 11
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0
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92
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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
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1
answer
298
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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
1
vote
1
answer
192
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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 ...
- 2,247
2
votes
1
answer
115
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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:
...
- 560
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41
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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 ...
- 11
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1
answer
248
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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
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0
answers
152
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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
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0
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42
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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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1
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96
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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
4
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1
answer
489
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Python shorthand for tensor product (Kronecker product)
When using numpy or tensorflow in Python, we can simply write
C = A @ B
for matrix ...
- 161
1
vote
1
answer
251
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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)$$
I assume $\...
- 113
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1
answer
95
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Trying to simulate Weak Value Amplification using QuTiP
Weak Value Amplification is a procedure in which one consider a bipartite Hamiltonian of the form $H = g A \otimes B$, where $A$ is called system, $B$ is called meter and $g$ is the extremely small ...
- 159
2
votes
1
answer
314
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Defining dimension of an operator in qutip
My main question: Can someone please explain to me how the list of array is used to define the dimension in qutip?
Context:
If I have my density operator ...
- 79
-1
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1
answer
271
views
Find orthogonal state for random 7 qubit state
I have a system that generates a random 7 qubit state and I need a method to always find the orthogonal state.
I'm currently using python and qutip for this, representing this 7 qubit state by a 128-...
- 695
0
votes
1
answer
231
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Using entropy_mutual function in QuTiP
I am trying to calculate mutual entropies using QuTiP, but I am being unsuccessful so far. More specifically, I consider a 2^n x 2^n matrix representing the density operator of a n-qubit bipartite ...
- 3
2
votes
2
answers
272
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Is there quantum error correction code package for python
I'm working on the development of a new quantum error correction protocol that tries to maximize the coherence of the qubit. Is there a package for python, similar to qutip, that could help me in this ...
- 695
1
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0
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217
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Numerical methods for finding an eigen basis of a degenerate Liouvillian
I'm trying to find the steady-state of a master equation,
$$\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
303
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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
787
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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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3
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0
answers
114
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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 ...
- 31
2
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0
answers
44
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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 ...
- 389
1
vote
0
answers
56
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, ...
- 389
2
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0
answers
48
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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 ...
- 389
2
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0
answers
107
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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 ...
- 389
3
votes
0
answers
81
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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