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Results tagged with research-level
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user 184
The research-level tag applies to questions that arise in graduate and post-secondary work. These questions often require domain-specific knowledge and could not be answered from a general source or may be beyond the level typically covered by Wikipedia and other popular sources. Research-level questions should not require new or groundbreaking research and results to answer.
7
votes
6
answers
246
views
Papers and preprints worth reading, Jan-midFeb 2012 [closed]
Which recent (i.e. Jan-midFeb 2012) papers and preprint do you consider really worth reading?
References should be followed by a summary saying what is the result and (implicitly or explicitly) why i …
- 6,510
16
votes
6
answers
375
views
Multiqubit state tomography by performing measurement in the same basis
For a $n$-qubit state $\rho$ we perform all projective measurement consisting of one-particle measurements in the same basis, that is,
$$p_{i_1i_2\ldots i_n}(\theta,\varphi) = \text{Tr}\left \{ \rho …
- 6,510
7
votes
Is there a Majorana-like representation for singlet states?
In the general - the answer is no.
Majorana representation's key point is to express a composite state of $n$ qubits as $n$ points is such way, that action of a collective rotation (i.e. $|\psi \rang …
- 6,510
5
votes
Accepted
CHSH violation and entanglement of quantum states
In a paper C.-E. Bardyn et al., PRA 80(6): 062327 (2009), arXiv:0907.2170, they discuss constrains on the state, given how much the CHSH equality is violated ($S=2+c$), but without putting any assumpt …
- 6,510
20
votes
2
answers
4k
views
Theoretical penetration limit for evanescent waves
Consider a problem in classical electrodynamics, when a monochromatic beam experiences total internal refraction when traveling from a medium with $n>1$ to a medium with refractive index $1$ - see sch …
- 6,510
11
votes
1
answer
411
views
Which qubit states are accessible with linear optics operations?
Given a quantum state of $n$ qubits, and being restricted to linear optics (that is, the output annihilation operators are linear combinations of the input annihilation operators):
Which states are …
- 6,510
10
votes
1
answer
174
views
Renyi fractal dimension $D_q$ for non-trivial $q$
For a probability distribution $P$, Renyi fractal dimension is defined as
$$D_q = \lim_{\epsilon\rightarrow 0} \frac{R_q(P_\epsilon)}{\log(1/\epsilon)},$$
where $R_q$ is Renyi entropy of order $q$ an …
- 6,510
33
votes
7
answers
2k
views
An entropy of the Wigner function
Is there an entropy that one can use for the Wigner quasi-probability distribution?
(In the sense of a phase-space probability distribution, not - just von Neumann entropy.)
One cannot simply use $\i …
- 6,510
8
votes
3
answers
505
views
Constructing a Hamiltonian (as a polynomial of $q_i$ and $p_i$) from its spectrum
For a countable sequence of positive numbers $S=\{\lambda_i\}_{i\in N}$ is there a construction producing a Hamiltonian with spectrum $S$ (or at least having the same eigenvalues for $i\leq s$ for som …
- 6,510
14
votes
1
answer
492
views
Majorana-like representation for mixed symmetric states?
Is there a generalization of the Majorana representation of pure symmetric $n$-qubit states to mixed states (made of pure symmetric $n$-qubit)?
By Majorana representation I mean the decomposition of …
- 6,510
2
votes
Accepted
Schwinger representation of operators for n-particle 2-mode symmetric states
The postulated relation is true, and not only for qubits, but arbitrary d-level systems. It took me some time to actually show it (when solving Which symmetric pure qudit states can be reached within …
- 6,510
1
vote
1
answer
59
views
Name of a state with $d-1$ excitations, distributed uniformly among $n$ qudits
Is there a particular name for a quantum state of the form (up to the normalization):
$$\sum_{i_1+\ldots+i_n = d-1} |i_1\rangle |i_2\rangle \ldots |i_n\rangle$$
or was it studied is some papers?
Th …
- 6,510
1
vote
Accepted
Name of a state with $d-1$ excitations, distributed uniformly among $n$ qudits
So, out of lack an already established name, I called it excitation states in:
P. Migdał, J. Rodriguez-Laguna, M. Lewenstein,
Entanglement classes of permutation-symmetric qudit states: symmetric ope …
- 6,510
9
votes
1
answer
114
views
Many body quantum states analyzed as probabilistic sequences
Measurements of consecutive sites in a many body qudit system (e.q. a spin chain) can be interpreted as generating a probabilistic sequence of numbers $X_1 X_2 X_3 \ldots$, where $X_i\in \{0,1,\ldots, …
- 6,510
2
votes
Analyticity and Causality in Relativity
Analytic functions are functions which are locally given by a convergent power series.
Analyticity of a function does not does not imply that by knowing values of all derivatives one can determine va …
- 6,510