# Questions tagged [cq-states]

For questions about classical-quantum (CQ) states.

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### How should $\rho(b,b')$ be interpreted in the context of classical-quantum state

I’m trying to understand the concept of a classical-quantum state as it is used in the context of quantum cryptography. In particular, I’m looking at the expression $CL.Enc_{pk}(\rho^M)$ from page 16 ...
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### Translating classical math and code to quantum math and code

I am starting to see a lot of classical quantitative problems such as linear regression being represented in quantum math, which suggests that almost anything based on frequentist statistics could be ...
144 views

### How to copy value from classical register to quantum register?

I have 1-qubit of quantum register and 2-bit of classical register. I have this simple algorithm: First, I'm doing simple process for q[0] with NOT. Second, I want ...
1 vote
335 views

### Is there any real world problem where I can see quantum computing being better than classical computing?

Is there any paper or piece of code showing, on a REAL quantum computer, that a specific real world problem (possibly related to computer science, machine learning or finance and possibly NOT related ...
35 views

### What's the map from any linear classical codes to entanglement-assisted stabilizers codes

When a linear code is self-dual, its parity check matrix can be used to easily define a stabilizer code. From my understanding, thanks to entanglement-assisted stabilizer codes, it is possible to ...
493 views

### Real-life examples of classical-quantum channels

In quantum information theory, classical-quantum channels are considered to be channels whose input is the realizations $x\in\mathcal{X}$ of a classical random variable to a quantum state $\rho_x^B$, ...
561 views

### 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 ...
107 views

### Can error correction for a classical algorithm with bit flips be easier than for a general quantum circuit?

Assume one runs a purely classical algorithm on $n$ logical qubits on a physical device with some bit flip probability. Can implementing error correction in this case be any easier than in the case of ...
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### Quantum analogues of information theoretic measures: are log probabilities replaced with the density matrix?

Below is a question and an answer. How does quantum information relate to, diverge from or reduce to Shannon information, which used log probabilities? What people are more often interested in are ...
34 views

### Question about the practical use of super dense coding in information transmission [duplicate]

Question about the practical use of super dense coding in information transmission: We know that by using super dense coding it is possible to transmit 2n classical bits transmitting n qubits, ...
54 views

### Counting Achievable Operations

I'm struggling to find an analytic way to solve this problem. There are $4! = 24$ possible classical operations on the four 2-Cbit basis states. How many of these are achievable via the classical ...
299 views

### What is known about the quantum version of Schoening's algorithm for 3SAT?

Schoening's algorithm for 3SAT can be converted to a quantum algorithm.  The classical circuit representing a 3SAT expression in CNF form can be converted to a quantum version involving reversible ...
123 views

### Example of a quantum algorithm better than its classical counterpart which involves only $1$ qubit?

I was reading over the proof of the Deutsch-Jozsa algorithm, which in its simplest case, involves at least 2 qubits. Is there an example of a quantum algorithm that is better than it's classical ...
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### The effect of available information on random quantum channels

This question is about the effect of available information on random quantum channels. Suppose there are two black box devices. Device 1. We have a black box device with a single qubit in it. Once ...
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### What does superposition do for quantum probabilistic sampling?

The idea of a qubit being able to exist for several values between 0 and 1 (superposition) makes it sound like it can do alot for probabilistic math problems, but for one task that comes instantly to ...
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### Quantum Optimization algorithms

The Harrow-Hassidim-Lloyd (HHL) algorithm for quantum matrix inversion (linear algebra) bridges classical math to quantum math and has been adopted for quantumizing many classical applications, such ...
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### Classical and quantum limits to classical copying?

The no-cloning theorem can be sharpened to give quantitative bounds on the fidelity with which an arbitrary quantum state can be copied. Is there a similar picture available for classical copying? ...
I have this cq-state: $$\frac{1}{2} \times (|0\rangle \langle0|_A \otimes \rho^0_E + |1\rangle \langle1|_A \otimes \rho^1_E)$$ Where Alice (A) is classical and an adversary Eve (E) has some ...