Qubit.java

/*-
 * #%L
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 * Copyright (C) 2020 Johan Vos
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package org.redfx.strange;

/**
 * <p>Qubit class.</p>
 *
 * @author johan
 * @version $Id: $Id
 */
public class Qubit {

    private Complex alpha;
    private Complex beta;

    private double theta = 0;
    private double phi = 0;
    
    private boolean measured = false;
    private boolean measuredValue;
    
    private double prob;

    /**
     * Creates a qubit. The qubit will be in the |0&gt; state
     */
    public Qubit() {
        this.alpha = Complex.ONE;
        this.beta = Complex.ZERO;
    }

    /**
     * Creates a qubit with an initial value for alpha.
     * The initial state of the qubit is ralpha |0&gt; + (1-ralpha^2)^(1/2) |1&gt;
     *
     * @param ralpha the real part of the alpha coefficient in alfa |0&gt; + beta |1&gt;
     */
    public Qubit (double ralpha) {
        this.alpha = new Complex(ralpha,0);
        this.beta = new Complex(Math.sqrt(1 - ralpha*ralpha), 0);
    }

    private double calculate0() {
        return Math.cos(theta/2);
    }
    
    private Complex calculate1() {
        double s = Math.sin(theta/2);
        return new Complex(Math.cos(phi)*s, Math.sin(phi)*s);
    }
    
    /**
     * <p>setProbability.</p>
     *
     * @param p a double
     */
    public void setProbability(double p) {
        this.prob = p;
    }
    
    /**
     * Performs a measurement on this qubit.
     *
     * @return <code>0</code> or <code>1</code>
     */
    public int measure() {
//        if (measured) {
//            throw new IllegalStateException("Can't measure an already-measured qubit");
//        }
//        measured = true;
//        measuredValue = Math.random()< prob;
        return measuredValue ? 1 : 0;
    }
    
    /**
     * <p>Setter for the field <code>measuredValue</code>.</p>
     *
     * @param v a boolean
     */
    public void setMeasuredValue (boolean v) {
        this.measuredValue = v;
    }
    
    /**
     * <p>getProbability.</p>
     *
     * @return a double
     */
    public double getProbability() {
        return this.prob;
    }
    
    
    
    
}