Search Results
| Search type | Search syntax |
|---|---|
| Tags | [tag] |
| Exact | "words here" |
| Author |
user:1234 user:me (yours) |
| Score |
score:3 (3+) score:0 (none) |
| Answers |
answers:3 (3+) answers:0 (none) isaccepted:yes hasaccepted:no inquestion:1234 |
| Views | views:250 |
| Code | code:"if (foo != bar)" |
| Sections |
title:apples body:"apples oranges" |
| URL | url:"*.example.com" |
| Saves | in:saves |
| Status |
closed:yes duplicate:no migrated:no wiki:no |
| Types |
is:question is:answer |
| Exclude |
-[tag] -apples |
| For more details on advanced search visit our help page | |
Results tagged with density-operator
Search options not deleted
user 251599
The density operator describes a quantum system in a (in general mixed) state.
2
votes
2
answers
197
views
Why is this the right form for the density operator in "classical" mixture cases?
It is well known that the set of density operators $\{\rho\}$ for a quantum theory form a convex set. As I have seen them defined, we simply say that a state corresponds to some linear operator $\rho$ …
- 1,261
3
votes
0
answers
118
views
Can a mixed state be a stationary state?
If we define a stationary state as a state in which the probability distributions for every observable are constant in time, is it fair to say that a mixed state can also be a stationary state? One us …
- 1,261
2
votes
2
answers
147
views
Mixed-State Density Matrices Versus Physical Ensembles
I am trying to follow a discussion (distinguishing the two sorts of systems mentioned in the title of this question) in Schlossahuer's book, Decoherence: And the Quantum-To-Classical Transition. Schlo …
- 1,261
2
votes
1
answer
147
views
Does an entangled composite system necessarily imply a nonpure reduced density matrix for a ...
This question is motivated by understanding decoherence processes. Consider a bipartite quantum system $S$ composed of two subsystems, $S_{soi}$ (soi = system of interest) and $S_{env}$ (env = environ …
- 1,261
0
votes
1
answer
117
views
A general theorem about state operators as a convex set?
I am trying to convince myself of a general theorem which fully "defines" the set of state operators. It is easy to prove that any convex combination of valid state operators is also a valid state ope …
- 1,261
0
votes
0
answers
46
views
Collapse postulate in the density operator formalism [duplicate]
To the extent that the collapse postulate holds, textbooks will almost invariably restrict the discussion to contexts in which states are represented by normalized kets, so that the collapse postulate …
- 1,261
2
votes
0
answers
145
views
Showing there are infinitely many decompositions of a non-pure state [duplicate]
Consider Problem 2.10 from Ballentine (paraphrased):
Show (by constructing an example depending on a continuous parameter) that this can be done in infinitely many ways.
I'm not sure how to proceed. …
- 1,261
2
votes
1
answer
184
views
What is the most general mathematical structure for representing a state in QM?
In quantum mechanics textbooks which are a little more careful it is common to see it noted that a (pure) quantum state is not a vector $|\psi\rangle$ but rather a ray in Hilbert space, $c|\psi\rangle …
- 1,261
1
vote
1
answer
83
views
If a state operator factors, then it factors into partial state operators in particular -- why?
Suppose that we have a state operator for a bipartite quantum system $\rho = A \otimes B$. As far as I know, one must then have in particular $\rho^{(1)} = A$; that is, if a state operator factors the …
- 1,261
6
votes
6
answers
441
views
On state transformations and the requirement of space-time invariance in (non-relativistic) ...
I am trying to follow the development in Ballentine's Quantum Mechanics: A Modern Development but am struggling a lot. Please excuse my attaching of a picture of the development, but my question quite …
- 1,261
4
votes
1
answer
248
views
Is a state being unentangled equivalent to statistical independence for all pairs of subsyst...
I imagine the answer is yes since, if so, the definition of unentangled is rather non-obvious and yet it gives an operational way to check for statistical independence.
I am working with the standard …
- 1,261