# Questions tagged [quantum-neural-network]

A machine learning model or algorithm that combines concepts from quantum computing and artificial neural networks encompassing a variety of ideas, ranging from quantum computers emulating the exact computations of neural nets, to general trainable quantum circuits that bear only little resemblence with the multi-layer perceptron structure.

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### Categories and types of quantum inspired algorithms

I have a question concerning "quantum-inspired" algorithms. There seem to be several types of algorithms that fall into this category. Some examples are: Ewin's dequantized algorithms ...
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### Understanding the definition of quantum neural network of Abbas et al. 2020

My Question based on this Paper https://arxiv.org/pdf/2011.00027.pdf "Power of Quantum Neural Networks" - Section 2. So I know that there are different ways to implement Neural Networks into ...
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### Computing expectation value of product of observables in PennyLane

In PennyLane, the following circuit returns the expectation value of the PauliZ observable on qubit (wire) 1: ...
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269 views

### Does TensorFlow Quantum tfq.convert_to_tensor work on custom gates?

I'm trying to use Cirq with TensorFlow Quantum to simulate a variational quantum classifier. There's a tutorial on the TFQ website on building a quantum neural network to classify a simplified version ...
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### Data encoding in the quantum perceptron model

In this paper, this figure shows the perceptron model used for quantum neural network. When realizing the inner product between weight vector and input vector, it defines a unitary transformation $U_W$...
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### Label function for a QNN designed to classify bit strings

The paper can be found https://arxiv.org/pdf/1802.06002.pdf here. They say that for each binary label function $l(z)$ where $l(z)=−1$ or $l(z)=1$, there exists a unitary $U$ such that, for all input ...
114 views

### Graph Limits in Quantum Computing

Lovasz's book Large networks and Graph Limits mentions that their study of graph limits is motivatived applications to quantum computers, statistical physics, and models for the internet. They don't ...
84 views

### Equivalencies between neural networks and quantum neural networks

TL;DR - Quantum neural networks use a few qubits, gates and simple quantum circuits. Regular neural networks use real numbers (composed of many bits), nonlinear functions on real numbers and very ...
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### Why does the parameter circuit include both the positive and negative shift terms?

In the derivation of the parameter shift rules in the original paper, the Hermitian generator $G$ of any unitary $U(\theta)=\exp[-i\theta G]$ satisfies  U(\pm\frac{\pi}{4r})=\frac{1}{\sqrt{2}}(I\mp\...
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### Is entanglement trainable?

There exists a famous result from Google that the gradients of the parameters of quantum neural networks (QNN) vanish exponentially with the number of qubits in the quantum circuit. Their result ...
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### What is a "repeat until success quantum circuit" in quantum neural networks?

I am working now on a quantum neural network project and want a deep explanation on the Repeat Until Success circuit. What I know about this circuit is that it allows a nonlinear activation function ...
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### How to add noise mode in Sampler (SamplerQNN) in qiskit for quantum neural network?

I would like to add a noise model to one of the tutorial examples of quantum machine learning in the Qiskit site (PyTorch QGAN implementation). I used the following codes ...
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### Quantum Convolutional Neural Network not producing gradients

I am trying to bulid a quantum convolutional neural network for image classification with Pennylane and Keras but the model isn't training and I keep getting the warning: WARNING:tensorflow:Gradients ...
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### How to take gradient of the tfq.layers.State output?

I am using the following code for building a quantum circuit as a custom tf.keras.layers.Layer: ...
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### How can we compute the gradient in a Quantum RNN?

I was looking into implementing a quantum recurrent neural network (QRNN) for a project, but I have some doubts about the computation of the gradient. There are a few papers that have implemented a ...
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### Adding trainable weights to feature inputs for a CircuitQNN?

Currently I'm trying to get together a QNN that can be trained to classify the normalized (-1, 1) IRIS Dataset on all 3 classes. For this I am using Qiskit's ...
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### What is the input for the interpret of Quantum Variational Regressors?

I'm trying to implement my first variational regressor using qiskit. I would like to understand how the interpret of a CircuitQNN works. I need to define an interpret that works on the amplitudes of a ...
1 vote
362 views

### How to upload our dataset using pytorch when it is not present in torchvision?

I am trying to upload my dataset(SWELL-KW) instead of MNIST in "Hybrid quantum-classical Neural Networks with PyTorch and Qiskit" provided by IBM qiskit but it says ...
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1 vote
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### Quantum neural networks and quantum kernels deal with nonlinearities

I'm trying to understand quantum neural networks from reading Alchieri et al.'s review paper. The following paragraph describes the differences between classical and quantum neural networks: Also, ...
1 vote
69 views

### Unitary operations in a Quantum Neural Network

I'm currently reading Classification with Quantum Neural Networks on Near Term Processors and I'm having trouble with one of the calculations. The system is composed of $n+1$ qubits, $n$ of those are ...
1 vote
281 views

### What are "unbounded loss functions" and "unbounded operators"?

I am reading this paper: Quantum Generative Training Using Rényi Divergences. In it, the authors mention the following multiple times: "...an unbounded loss function can circumvent the existing ...
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1 vote
26 views

### Adding an Extra Qubit into a Quantum Circuit

I am a beginner in quantum computing and am learning about parameterised quantum circuits (in the context of quantum neural networks). What effect does adding an extra qubit into a quantum circuit ...
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1 vote
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### Effect of error correction gates in QCNN

In Iris Cong et. al. (2019) they propose a Quantum Convolutional Neural Network that utilizes mid-circuit measurements to control an error-correcting ansatz $V_j$. This is the equivalent of a pooling ...
1 vote
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### Measuring a single-qubit PauliZ using Qiskit's EstimatorQNN

I am currently working with the EstimatorQNN from Qiskit to construct a Quantum Neural Network using a custom Parametrized Quantum Circuit. But I want to change the ...
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1 vote
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### Where is the input data X in the CV-QNN as presented in Pennylane?

I am referring to the tutorial of CV-QNN in Pennylane(Strawberry Fields). Each layer of CV-QNN can perform the operation below. Unlike other quantum neural network tutorials, where the input X and y ...
1 vote
41 views

### Quantum Generative Adversarial Network does not converge

I have built a quantum generative adversarial network model, in which the generator and the discriminator, both are quantum based model. The parametrized quantum circuit/ansatz of these two models are ...
1 vote
272 views

### How to train a Quantum Neural network for regression model in supervised learning

We want to train a parameterised circuit(which is our neural network - from this paper. Now our final circuit looks a little like Let's say there are n training cases. So I have n |gt> vectors ...
688 views

### How do I calculate the amount of qubits required for Image Classification with a Quantum Convolutional Neural Network?

I'm relatively new to the topic of QCNNs and I wanted to understand how the number of qubits is selected in the encoded quantum layer. Like is it based on the image we want to encode? What is the ...
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### What are necessary and sufficient conditions for the output of a parametrized unitary $U(\theta)$ to be smooth?

Let us consider a unitary $U$ parameterised by $\theta \in \mathbb{R}$, i.e, $U(\theta)$. What are the necessary and sufficient conditions for the output states of this unitary to be smooth? One ...
25 views

### Quantum data as input for Quantum Neural Net

I'm new to quantum machine learning, and I wanted to know how quantum data is processed in a quantum neural net. For example, if I am training a QNN to classify entangled circuits from non-entangled ...