Quantum Computing Stack Exchange
Quantum Computing Stack Exchange

Questions tagged [encoding]

For questions that are about representing a physical quantity as a quantum state. For instance, questions about amplitude encoding, state encoding or fermion to qubit encoding should use this tag.

24 questions
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Preparation of logical state with qLDPC code

I'm recently learning qLDPC code. Although I've seen literature talking about the code construction, parity check, possible logical operation and decoding. How exactly do I prepare e.g. a logical phi state in the Hypergraph Product code? ... I…
AndyLiuin
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How does one perform amplitude encoding using only unitary gates?

How does one perform amplitude encoding using only unitary gates ? Could you show me a concrete example ?
Duen
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A matrix that can be simultaneously diagonalisable can induce a decomposition of its space

Potentially "space" is not the correct word to use in the title, please correct if wrong I am reading "Quantum Error Correction Via codes over Gf(4)" and I came across something I can't quite get straight in my head. Take $E$ to be the quantum error…
am567
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How to implement the Circuit of Steane code for Quantum Error Correction?

I have referred this same question here 'Circuit for implementing Steane's code for Quantum Error Correction' . But the answer discusses the circuit to compute the syndrome and not clearly the encoding part of the Steane code. I have searched for…
chetan waghmare
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How to map QUBO to Ising and account for the sign change in non-diagonal elements?

A question that has been bugging my mind in quantum annealing is: Assume we have a QUBO matrix $Q_{ij}$ with non-zero non-diagonal elements which have different signs, that is $Q_{ij}<0$ for some $i\neq j$ and $Q_{nm}>0$ for some $m\neq n$. How can…
Nikolaos Petropoulos
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Wrong encoding circuit for $[[5, 1, 3]]$ code in Gottesman's thesis

In Chapter 4 of Daniel Gottesman's thesis, he gave an encoding circuit for the famous $[[5, 1, 3]]$ code. Note that in this figure, $R$ is the Hadamard gate. However, this circuit seems not working properly to me. An encoding circuit should…
Yunzhe
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Visualize the qubit state after amplitude encoding

I trying to visualize qubits state after amplitude encoding. I have the following code which takes the 8 feature [1/2, 1/2, 1/2, 1/2,1/2, 1/2,1/2,1/2] and encodes into 3 qubits. I now get the output [0.35355339+0.j 0.35355339+0.j 0.35355339+0.j…
kannan quantum
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Grover's algorithm to maximize QUBO functions

I'm trying to maximize a QUBO function f(x,y,z) = 3xy + 4xz - 3yz + 11y + z. How can I use Grover's algorithm to do this? I've been told to encode this cost function which I'm not sure of. And to use quantum annealing to maximize the cost function.…
Van Peer
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Arbitrary Encoding - how 3 qubits can encode 12 distinct features?

I am trying to understand how Arbitrary Encoding, as described in this qiskit site https://learn.qiskit.org/course/machine-learning/data-encoding, works and can encode 12 features using only 3 qubits. I can understand that encoding 2 features per…
user22271
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Why does manually applying Hadamard + RZ gate give different results than Qiskit ZFeatureMap?

I'm trying to understand how different quantum feature maps encode data. As part of this, I'm attempting to manually construct the same statevector that Qiskit's ZFeatureMap produces, using my own implementation with basic quantum gates (Hadamard…
FelipeAmorim
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Can one setup a superposition of finite field elements in polynomial time

I was wondering if we can setup a superposition of the elements of a finite field $\mathbb{F}_p$ with $p \in \mathbb{P}$ in polynomial time. I am only interested in the prime case, but if you want to generalise to $p^k$ feel free. i.e. I am…
Ramezzez
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Angle encoding and decoding for an $n$-qubit system

I am completely new to the field of quantum computing and am working on a project involving image processing. I need to encode the pixels of an image into a quantum system using different methods such as amplitude, angle and Hamiltonian encoding and…
George Ziavras
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Do encoding schemes for variational algorithms apply to annealing methods (e.g. DWave)?

I understand there are some efficient encoding schemes for variational algorithms, that attempt to approximate the variational state using fewer qubits. I'm thinking of 2 papers in particular, which are very closely…
IsalanOnkar
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How to best represent 5-Qbit codeword operator in Qiskit

We learned that in the 5-Qibit error correcting code, the logical zero state $ | \bar{0} \rangle $ is encoded in the form of $ \frac{1}{4} (\mathbb{1}+M_0)(\mathbb{1}+M_1)(\mathbb{1}+M_2)(\mathbb{1}+M_3) | 00000 \rangle $ where $M_0 = Z_1X_2X_3Z_4,…
Blackwidow
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What do arbitrary encoding circuits provide?

I'm about to implement my first VQC for image classification and I'm trying to figure out which data encoding method could fit better the problem. From what I've understood, there are three main approaches to encode classical data into quantum…
Paul
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