error in quantumCircuit Function?

I have tried example in this link

https://www.mathworks.com/help/matlab/math/solve-xor-problem-using-quantum-neural-network.html?searchHighlight=quantum%20neural&s_tid=srchtitle_support_results_2_quantum%20neural

I try to deploy a Quantum Neural Network. But the class PCQ layer always erorrs. I do everything same like in example and here is the class

classdef PQCLayer < nnet.layer.Layer
    % Custom PQC layer example.

    properties (Learnable)
        % Define layer learnable parameters.
        A
        B
    end

    methods
        function layer = PQCLayer
            % Set layer name.
            layer.Name = "PQC";

            % Set layer description.
            layer.Description = "Layer containing a parameterized " + ...
                "quantum circuit (PQC)";

            % Initialize learnable parameter.
            layer.A = 1;
            layer.B = 2;
        end

        function Z = predict(layer,X)
            % Z = predict(layer,X) forwards the input data X through the
            % layer and outputs the result Z at prediction time.
            Z = computeZ(X,layer.A,layer.B);
        end

        function [dLdX,dLdA,dLdB] = backward(layer,X,Z,dLdZ,memory)
            % Backpropagate the derivative of the loss
            % function through the layer.
            %
            % Inputs:
            %     layer   - Layer though which data backpropagates
            %     X       - Layer input data
            %     Z       - Layer output data
            %     dLdZ    - Derivative of loss with respect to layer
            %               output
            %     memory  - Memory value from forward function
            % Outputs:
            %     dLdX   - Derivative of loss with respect to layer input
            %     dLdA   - Derivative of loss with respect to learnable
            %              parameter A
            %     dLdB   - Derivative of loss with respect to learnable
            %              parameter B

            s = pi/4;
            ZPlus = computeZ(X,layer.A + s,layer.B);
            ZMinus = computeZ(X,layer.A - s,layer.B);
            dZdA = X(1,:).*((ZPlus - ZMinus)./(2*sin(X(1,:).*s)));
            dLdA = sum(dLdZ.*dZdA,"all");

            ZPlus = computeZ(X,layer.A,layer.B + s);
            ZMinus = computeZ(X,layer.A,layer.B - s);
            dZdB = X(2,:).*(((ZPlus - ZMinus)./(2*sin(X(2,:).*s))));
            dLdB = sum(dLdZ.*dZdB,"all");

            % Set the gradients with respect to x and y to zero
            % because the QNN does not use them during training.
            dLdX = zeros(size(X),"like",X);
        end
    end
end

function Z = computeZ(X, A, B)
    numSamples = size(X,2);
    x1 = X(1,:);
    x2 = X(2,:);
    Z = zeros(1,numSamples,"like",X);
    for i = 1:numSamples
        circ = quantumCircuit(2);
        circ.Gates = [rxGate(1,x1(i)*A); rxGate(2,x2(i)*B); cxGate(1,2)];
        s = simulate(circ);
        Z(i) = probability(s,2,"0") - probability(s,2,"1");
    end
end

But here is the problem. Everything is okay but quantumCircuit doesnt work.

Error using trainNetwork (line 191)
Invalid network.

Caused by:
    Layer 'PQC': Error using the predict function in layer PQCLayer. The
    function threw an error and could not be executed.
        Undefined function 'quantumCircuit' for input arguments of type
        'double'.

        Error in PQCLayer>computeZ (line 72)
                circ = quantumCircuit(2);

        Error in PQCLayer/predict (line 27)
                    Z = computeZ(X,layer.A,layer.B);
 

Does anybody knows why i get this error?

I changed parameters of the quantumCircuit like

                    gates = [hGate(1); cxGate(1,2)];
                    c = quantumCircuit(gates);

but this time i get hGate unrecognized function error. I use Matlab 2024a why i get hese errors?

Answer 1

[Garmit Pant]

Hello Arda

I gather that you are trying to train and deploy a quantum neural network using MATLAB. To deploy a quantum neural network in MATLAB, you need to install the “MATLAB Support Package for Quantum Computing”.

The support package is required to run the “quantumCircuit” and “hGate” functions. The errors are resolved once the support package is installed.

gates = [hGate(1); cxGate(1,2)]; 
c = quantumCircuit(gates); 
plot(c) 

You can install the “MATLAB Support Package for Quantum Computing” using the “Add-On Explorer” or using the following link:

https://www.mathworks.com/matlabcentral/fileexchange/125425-matlab-support-package-for-quantum-computing

I hope you find the above explanation and suggestions useful!

[arda has]

Thank you