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1500 questions
6
votes
1 answer
Why is $P(1,2)_{\text{same}} = \frac{1}{4}$ and not $\frac{1}{2}$ in Preskill's Bell experiment?
Context:
Three coins on the table. Each is either heads or tails. You can
uncover any one of the three coins, revealing whether it is heads or
tails but then you choose two the other two coins disappear --- you'll
never know whetehr those…
Sanchayan Dutta
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6
votes
1 answer
How to create the oracle matrix in Grover's algorithm?
I'm trying to implement Grover's algorithm in pyQuil, but I'm having trouble creating the oracle matrix given the function $f$, where $f(x)=1$ if $x=w$ and $f(x)=0$ otherwise. In most of the implementations I've seen, either a mysterious oracle…
user5694
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6
votes
0 answers
Why can a point in anti-de Sitter space be modeled as a logical qutrit and how is its error correction done?
This isn't my area but the recent Quanta article How Space and Time Could Be a Quantum Error-Correcting Code struck me as interesting. They mention:
In their paper[1] conjecturing that holographic space-time and quantum
error correction are one…
Sanchayan Dutta
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6
votes
1 answer
Do weak measurements (with/without weak values) have any application in quantum computation?
I have seen their applications in quantum state tomography but not in computation as such.
RAMAN CHOUDHARY
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6
votes
1 answer
What happens with first phase factor in QFT?
I'm using Mermin's Quantum Computer Science book to understand Shor's algorithm, but I can't figure out why one of the phase factors drops out of the probability for measuring a certain y.
This is the application of the QFT on the superposition of…
jvdh
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6
votes
1 answer
How to construct a quantum circuit (QIP system) for the graph non-isomorphism problem?
I'm having some trouble understanding quantum interactive proof systems (QIP systems) and the related circuit constructions. Interactive proof systems model these type of situations:
Interactive proof systems:
To say a promise problem…
Sanchayan Dutta
- 17,497
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6
votes
2 answers
How to translate matrix back into Dirac notation?
In Circuit composition and entangled states section of Wikipedia's article on Quantum logic gates the final result of a combined Hadamard gate and identity gate on $|\Phi^{+}\rangle$ state is:
$ M \frac{|00\rangle + |11\rangle}{\sqrt{2}} =…
Michał Zając
- 63
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6
votes
2 answers
Does quantum computing relate to stochastic computing in any way?
I'm a bit familiar with the concept of stochastic computing, where numbers are stored in large bit streams called "Stochastic Numbers", which represent numbers in the domain $[0,1]$ typically.
The Wikipedia article on stochastic computing summarizes…
DanBC
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6
votes
2 answers
Defining entanglement for systems with more than two qubits
Introductory textbooks I've read define entanglement as when your product state cannot be factored into the tensor product of individual quantum states. But consider a three-qbit system:
$$C_{2,0}H_2|000\rangle = \begin{bmatrix} \frac{1}{\sqrt{2}}…
ahelwer
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6
votes
2 answers
Efficient implementation of the Clifford group for $n$ qubits
I'm looking for an efficient implementation of the Clifford group $\mathcal{C}_n$
of $n$ qubits.
The Clifford group $\mathcal{C}_n$ has stucture $(2_+^{1+2n} \circ C_8).Sp(2,n)$,
where $2_+^{1+2n}$ denotes an extraspecial 2 group of $+$ type,…
Martin Seysen
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6
votes
0 answers
How many qubits and how many gates, are required for finding the eigenvalues of a matrix?
Say I have an $N \times N$ matrix and I want to know the eigenvalues to a precision of $\pm \epsilon$. How many qubits and how many gates do I need?
Pablo LiManni
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6
votes
1 answer
Is the set of classical-quantum states convex?
I read about the classical-quantum states in the textbook by Mark Wilde and there is an exercise that asks to show the set of classical-quantum states is not a convex set. But I have an argument to show it is a convex set. I wonder whether I made a…
qquery
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6
votes
3 answers
Classical complexity for Simon's problem
Simon's problem is that you are given a function $f : \{0,1\}^n \to \{0,1\}^n$ such that $f(x)=f(y)$ if and only if $x \bigoplus y$ is either $0^n$ or some unknown $s$. The problem is to find $s$. If $s=0^n$, then $f$ is 1 to 1 otherwise 2 to…
Tech Solver
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6
votes
4 answers
Measuring qubits in QuTiP
How can you measure qubits in QuTiP?
As far as I have seen you can define a Hamiltonian and let it evolve in time. It is also possible to define a quantum circuit, however, measuring and running it is not possible.
Does anyone know how to do this?…
nippon
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6
votes
2 answers
How does $\mathcal E(\rho)=\mathrm{Tr}_{env}[U(\rho\otimes\rho_{env})U^\dagger]$ turn into $P_0\rho P_0+P_1\rho P_1$?
In the Quantum Operations section in Nielsen and Chuang, (page 358 in the 2002 edition), they have the following equation:
$$\mathcal E(\rho) = \mathrm{Tr}_{env} [U(\rho \otimes \rho_{env})U^\dagger]$$
They show an example with
$\rho_{env} =…
Mahathi Vempati
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