Unanswered Questions
69 questions with no upvoted or accepted answers
19
votes
0answers
375 views
Explicit Lieb-Robinson Velocity Bounds
Lieb-Robinson bounds describe how effects are propagated through a system due to a local Hamiltonian. They are often described in the form
$$
\left|[A,B(t)]\right|\leq Ce^{vt-l},
$$
where $A$ and $B$ ...
13
votes
0answers
168 views
Explicit Conversion Between Universal Gate Sets
I'm interested in the conversion between different sets of universal gates. For example, it is known that each of the following sets is universal for quantum computation:
$\{T,H,\textrm{cNOT}\}$
$\{H,...
11
votes
0answers
191 views
Quantum simulation of environment-assisted quantum walks in photosynthetic energy transfer
This question is related to Can the theory of quantum computation assist in the miniaturization of transistors? and Is Quantum Biocomputing ahead of us?
About 10 years ago, several papers discussed ...
10
votes
0answers
119 views
Superconducting qubit researchers: Do your TLS's move?
I have a superconducting system with tens of qubits, each of which can be tuned using DC flux.
One of the main tasks for coherent manipulation of the qubits is to find good idling frequencies and ...
9
votes
0answers
114 views
Quantum walk with binary tree
I’m trying to grok quantum walks, and would like to create an example that walks a perfect binary tree to find the one and only marked leaf node. Is this possible? If so, suppose the depth of the tree ...
8
votes
0answers
121 views
Quantum Walk: Why the need of adding “tail” nodes to the root?
As stated in the question, I have found in several papers (e.g. 1, 2) that in order to perform a quantum walk on a given tree it is necessary to add some nodes to the root $r$, say $r^{'}$ and $r^{"}$....
7
votes
0answers
90 views
Quantum algorithms for problems outside NP
What is known about quatum algorithms for problems outside NP (eg NEXP-complete problems), both theoretically like upper & lower speedup bounds and various (im)possibility results, as well as ...
7
votes
0answers
87 views
Estimate/determine Bures separability probabilities making use of corresponding Hilbert-Schmidt probabilities
For two-qubit states, represented by a $4\times 4$ density matrix, the generic state is described by 15 real parameters. For ease of calculation, it can help to consider restricted families of states, ...
7
votes
0answers
50 views
Active improving of nanodiamond surfaces for NV centers?
This question is related (and complementary) to "Passive improving of nanodiamond surfaces for NV centers?".
Nitrogen-Vacancy centers (NVs) have astonishing quantum properties, which make them ...
7
votes
0answers
121 views
Entanglement transfer of spin-entangled triplet-pair states between flying qubits and stationary qubits
The context: We are in the solid state. After a photon absortion by a system with a singlet ground state, the system undergoes the spin-conserving fission of one spin singlet exciton into two spin ...
7
votes
0answers
115 views
What is the difference between quantum control and quantum optimal control?
In the context of quantum control theory, it is common to see references to both quantum control and quantum optimal control (e.g. 0910.2350 or the guide on qutip quantrum control functions).
...
6
votes
0answers
66 views
Shor's algorithm weaknesses & uniqueness of close rational
I'm working through a problem set, and am stuck on the following problem:
a) What can go wrong in Shor’s algorithm if Q (the dimension of the Quantum Fourier Transform) is not taken to be ...
6
votes
0answers
67 views
Does the GLOA have any advantage over the Solovay-Kitaev algorithm?
The Solvay Kitaev algorithm was discovered long before the Group Leaders Optimization algorithm and it has some nice theoretical properties. As far as I understand, both have exactly the same goals: ...
6
votes
0answers
50 views
Discrepancy regarding Husimi Probability distribution
I am trying to simulate a system of j qubits and for visualization of the dynamics considering the Husimi distribution of the state.
To carry out the projection ...
6
votes
0answers
58 views
How significant are the variants of Grover's Algorithm?
I found a paper by Grover titled "How significant are the known collision and element distinctness quantum algorithms?", in which he expressed criticism to several famous algorithms, including ...
