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.
64
questions
1
vote
0
answers
14
views
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 $+\hbar\omega_0/2$...
- 11
1
vote
0
answers
14
views
Is it possible to find out the number of timesteps taken by the mesolve/sesolve method in QuTip?
I am simulating a Quantum System in QuTip using qutip.sesolve. As far as I understand it, the solver propagates the state into the future using time steps of ...
- 11
1
vote
0
answers
34
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(...
- 77
1
vote
0
answers
17
views
Qutip - Use of Create vs Fock state functions
I'd like to understand the physical difference between the states created using the following two means, i.e. state1 and state2:
...
2
votes
0
answers
34
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. ...
- 179
2
votes
0
answers
33
views
Weird behavior when simulating vacuum Rabi oscillation on QuTip
I've been playing around with vacuum Rabi oscillation on QuTip and found an odd behavior.
My Hamiltonian is as follows:
$$ H=\omega_n n^\dagger n + \omega_c c^\dagger c -6K(n+n^\dagger)^4 - g(n^\...
- 21
2
votes
0
answers
75
views
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...
...
- 21
1
vote
1
answer
36
views
Calculate average fidelity of QobjEvo
I am using QuTip to simulate a quantum gate, and I want to calculate the average fidelity of the gate.
I have the Hamiltonian, the interaction time, and Liouvillian modeling the decoherence.
Is there ...
- 11
0
votes
1
answer
96
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 ...
- 111
1
vote
0
answers
9
views
From what distribution is QuTip's rand_herm sampled from?
I am trying to figure out how QuTip samples Hamiltonians using its rand_herm function. It seems to use SciPy's sparse.rand ...
- 199
1
vote
0
answers
37
views
0
votes
0
answers
92
views
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 ...
0
votes
1
answer
68
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 ...
1
vote
0
answers
19
views
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
1
vote
0
answers
28
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
28
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?
2
votes
1
answer
120
views
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 ...
- 199
1
vote
1
answer
106
views
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. ...
- 177
1
vote
0
answers
54
views
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
vote
1
answer
40
views
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 ...
- 173
1
vote
2
answers
208
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. ...
- 767
0
votes
1
answer
27
views
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
vote
0
answers
44
views
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 ...
- 171
2
votes
0
answers
77
views
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 ...
- 325
0
votes
1
answer
70
views
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 ...
- 199
0
votes
1
answer
170
views
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
vote
0
answers
147
views
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
1
vote
0
answers
41
views
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) ...
- 2,327
2
votes
1
answer
369
views
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 ...
- 536
4
votes
0
answers
147
views
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
1
vote
1
answer
81
views
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
1
answer
298
views
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 ...
- 288
2
votes
1
answer
364
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:
...
- 288
1
vote
1
answer
328
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 ...
- 11
1
vote
0
answers
118
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
371
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
1
vote
1
answer
300
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 ...
- 2,327
2
votes
1
answer
151
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:
...
- 614
1
vote
0
answers
50
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 ...
- 11
1
vote
1
answer
312
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
211
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
44
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 ...
- 142
2
votes
1
answer
131
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
677
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
345
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
109
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 ...
- 169
2
votes
1
answer
400
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
-1
votes
1
answer
329
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-...
- 715
0
votes
1
answer
285
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 ...
- 3
2
votes
2
answers
294
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 ...
- 715