All Questions
Tagged with wigner-transform operators
21
questions
6
votes
1
answer
210
views
What is the Wigner representation of $\left(\hat{x}^2+\hat{p}^2\right)^n$?
I would like to calculate the Wigner representation of the operators $\left(\hat{x}^2+\hat{p}^2\right)^3$ and $\left(\hat{x}^2+\hat{p}^2\right)^4$. I know at least two ways to do it, but both rely on ...
- 73
5
votes
1
answer
1k
views
Bopp operators and Wigner-Weyl representation
I am learning about the Wigner-Weyl transformations to move a $c$-number Lindblad operator $A(x,p)$ back into operator form. As far as I know, to move back and forth normally requires a four variable ...
- 113
4
votes
2
answers
1k
views
Examples of Weyl transforms of nontrivial operators
I've been able to find examples of Weyl transforms of operators like $\hat{x}$,$\hat{p}$, and $\hat{1}$, but not anything more complicated. Are there derivations of the Weyl transforms of more ...
- 5,725
4
votes
1
answer
441
views
Non-commutative Fourier transform of an operator
Wigner-Weyl transform relates an operator to its distribution function in phase space through an operator Fourier transform which is said to be non-commutative.
$$
\hat{\rho} \xrightarrow[non-comm]{...
- 199
4
votes
1
answer
365
views
How can I take the Wigner transform of an operator with an absolute value?
I want to be able to find the Wigner transforms of operators of the form $\Theta(\hat{O})$, where $\Theta$ is the Heaviside function and $\hat{O}$ in general depends on both $x$ and $p$. For the ...
- 5,725
3
votes
0
answers
156
views
Is there a canonical Taylor expansion for operators in terms of $X$ and $P$?
Consider the algebra of operators acting on wavefunctions ($L^2(\mathbb{R})$) generated by $X$ and $P = -i\hbar (\partial/\partial x)$. For some operator $A$ in this algebra, or possibly in a ...
- 3,684
3
votes
0
answers
74
views
Are Wigner functions of any Unitary operator in $B(L^{2}(\mathbb{R}))$ in $L^{2}(\mathbb{R}^{2})$?
Are Wigner functions of any Unitary operator in $B(L^{2}(\mathbb{R}))$ in $L^{\infty}(\mathbb{R}^{2})$?
i.e.
Let $e^{iA} \in B(L^{2}(\mathbb{R}))$. Define the Wigner function (Wigner transform) as ...
- 90
2
votes
2
answers
269
views
General quantum operator
Is it true that any operator can be expressed as
(e.g. in one dimension)
$$\hat{A}=\sum_{n=0, \, m=0}^{\infty}c_{n,m}\hat{x}^n\hat{p}^m \, ?$$
It seems true because any classical observable is a ...
- 33
2
votes
2
answers
111
views
Dirac delta of operators multiplying matrix element
In playing around with the Wigner-Weyl correspondence, I found myself needing to perform an integral of exponential operators, which I am confused about. TLDR: help to evaluate $$\int d{x}dy\ \delta(x\...
- 173
2
votes
0
answers
89
views
Fourier Transform of $s$-ordered Characteristic Function
In the book, "Quantum Continuous Variables (A Primer of Theoretical Methods)" by Alessio Serafini, on page 70, he defines an $s$-ordered characteristic function to be:
$$
\chi_s(\alpha)=\...
1
vote
1
answer
147
views
Wigner image of the product of two operators
If we know the Wigner image of $\hat{A}$ and $\hat{B}$, how do we calculate the Wigner transform of $\hat{A}\hat{B}$?
- 121
1
vote
2
answers
172
views
Basic confusion with quantum mechanical operators
Given a classical observable, $a(x,p),$ Weyl quantization gives the correspondent QM observable as:
$$\langle x | \hat{A} | \phi \rangle=\hbar^{-3}\int \int a \left(\frac{x+y}{2},p\right)\phi(y) e^{2\...
- 1,262
1
vote
2
answers
85
views
Wigner transform of $O_1 O_2$ in terms of Wigner transforms of $O_1$ and $O_2$?
The Wigner-Weyl transform of a quantum operator $O$ is defined as
$$
W[O](q,p) = 2 \int_{-\infty}^{\infty} dy\ e^{- 2 i p y} \langle q + y | O | q - y \rangle \ dy
$$
and then given a density matrix $\...
- 3,719
1
vote
1
answer
347
views
Wigner map of the product of two operators
Does anyone know how to prove that for the product of two operators $\hat{A}\hat{B}$ the Weyl-Wigner correspondence reads
$$
(AB)(x,p) = A\left (x-\frac{\hbar}{2i}\frac{\partial}{\partial p}, p+\frac{\...
- 793
1
vote
1
answer
122
views
Obtaining the star product from the Weyl quantisation of the product of two symbols
It can be shown (Groenewold 1946) that the Weyl quantisation of the product of two Weyl symbols is given by
$$ [A(\textbf{r})B(\textbf{r})]_{w}=\frac{1}{(2\pi)^{2}}\int_{\mathbb{R}^{4}}e^{i\...
- 941