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1500 questions
8
votes
1 answer
What is "linear" in linear entropy?
Why is the linear entropy, defined by $S_L = 1 - \textrm{Tr} \rho^2$, called linear?
Rob
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8
votes
2 answers
What is (formally) a transversal operator?
This question concerns about a formal definition of transversal operator.
I understood that transversal operator are a group of operators which are efficient in terms of circuit depth and can be used as logical operators for stabilizer codes.…
Daniele Cuomo
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8
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1 answer
Are Absolutely Maximally Entangled states maximally entangled under all entanglement monotones?
In Ref. [1] absolutely maximally entangled (AME) states are defined as:
An $\textrm{AME}(n,d)$ state (absolutely maximally entangled state) of $n$ qudits of dimension $d$, $|\psi\rangle \in \mathbb{C}^{\otimes n}_d$, is a pure state for which every…
SLesslyTall
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8
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2 answers
Given an orthogonal projection $\Pi$, is $\|\Pi(\sigma-\rho)\Pi\|_1\le\|\sigma-\rho\|_1$ true?
Suppose I have an arbitrary orthogonal projector $\Pi$ and two density operators $\rho, \sigma$. Is it true that:
$$ ||\Pi (\sigma - \rho) \Pi||_1 \le || \sigma - \rho ||_1 $$
where $||\cdot||_1$ denotes the trace norm?
NYG
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8
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2 answers
What use cases are there for 127 qubit QPUs?
IBM have recently announced their 127 qubit Eagle processor. Other approaches, such as Rydberg arrays, have now 256 qubits, as for example in QuEra's QPU QPU.
While these are without a doubt outstanding techical acheivements, I am wondering what is…
Lior
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8
votes
3 answers
What is a "maximally mixed state"?
What is meant by maximally mixed states? Does this mean that there are partially mixed states?
For example, consider $\rho_{GHZ} = \left| {GHZ} \right\rangle \left\langle {GHZ} \right|$ and $\rho_W = \left| {W} \right\rangle \left\langle {W}…
Bekaso
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8
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1 answer
Quantum algorithm for linear systems of equations (HHL09): Step 1 - Number of qubits needed
This is a continuation of Quantum algorithm for linear systems of equations (HHL09): Step 1 - Confusion regarding the usage of phase estimation algorithm
Questions (contd.):
Part 2: I'm not exactly sure how many qubits will be needed for the Step 1…
Sanchayan Dutta
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8
votes
2 answers
How could a quantum network be constructed to handle 10,000 clients concurrently?
The C10k Problem is a classical computing problem whose name (C10k) is a numeronym for concurrently handling ten thousand connections.
How could a quantum network be constructed to handle 10,000 clients concurrently?
user820789
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8
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2 answers
Changing indices of qubits in QISKit
I was wondering if something like this is possible in QISKit: let's say we have two registers containing target and ancilla qubits:
$a_0$ -------------------
$a_1$--------------------
$\vdots$
$a_4$ ------------------
$t_0$ ------------------
$t_1$…
brzepkowski
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8
votes
1 answer
How to find a density matrix of a qubit?
If we are given a state of a qubit, how do we construct its density matrix?
Archil Zhvania
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8
votes
4 answers
Simulating a quantum circuit with decoherence and noise
Based on the answers given here and here, it is pretty clear that an arbitrary quantum circuit can be simulated with matrix algebra. The difficulty is that this assume perfect fidelity. I am unsure how to generalize this method to take into account…
Anna Naden
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8
votes
1 answer
Are Genetic Programming runtimes faster on QCs than on classical computers?
If this isn't known, would they theoretically be? I'm particularly interested in knowing whether a QC would be faster at evaluating the fitness function of the possible solutions than a classical machine
MenzerInternational
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8
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1 answer
What does "conjugation of coordinates" mean with respect to GF(4) (quantum) codes
In On the classification of all self-dual additive codes over $\textrm{GF}(4)$ of length up to 12 by Danielsen and Parker, they state:
Two self-dual additive codes over $\textrm{GF}(4)$, $C$ and $C^\prime$, are equivalent if and only if the…
SLesslyTall
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8
votes
1 answer
How to apply single and two qubit gates to 2 qubits multiple times?
Let's say we have the following quantum circuit:
Let's say we input the state $|00\rangle$ . Both of the $H$ gates produce the output $1/\sqrt{2}$, but which one of the following $2$ vectors is the input of $\operatorname{CNOT}$ gate:
$1:…
Archil Zhvania
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8
votes
2 answers
Practical Implementations of QECCs in IBM Q Experience
I am learning how to program the IBM Q Experience quantum computers in order to learn more about how does it work and in order to perform some experiments in it. By doing so I was wondering what are the most advanced things that have been done in…
Josu Etxezarreta Martinez
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