strange

Quantum Computing API and simulator for Java

This project defines a Java API that can be used to create Quantum Programs. A Quantum Program, defined by org.redfx.strange.Program can be executed on an implementation of the org.redfx.strange.QuantumExecutionEnvironment.

You can read more about Java and QuantumComputing in Quantum Computing in Action

Getting Started

Strange is distributed via Maven Central and can thus easily be used leveraging maven or gradle build software.

Using JBang

JBang makes it easy to run simple Java applications without setup hassle.

You can download JBang from jbang.dev.

The following code is a very simple Java application that is using Strange (and StrangeFX). Save this code in a file named ShortStrangeDemo.java and execute it by typing the following command in a terminal: jbang ShortStrangeDemo.java

//DEPS org.redfx:strangefx:0.1.4
import org.redfx.strange.*;
import org.redfx.strange.gate.*;
import org.redfx.strange.local.SimpleQuantumExecutionEnvironment;
import org.redfx.strangefx.render.Renderer;
import java.util.Arrays;

public class ShortStrangeDemo {
    public static void main(String[] args) {
Program p = new Program(2, new Step(new X(0)), new Step(new Hadamard(0), new X(1)));
        SimpleQuantumExecutionEnvironment sqee = new SimpleQuantumExecutionEnvironment();
        Qubit[] qubits = sqee.runProgram(p).getQubits();
        Renderer.renderProgram(p);
        Arrays.asList(qubits).forEach(q -> System.out.println("qubit with probability on 1 = "+q.getProbability()+", measured it gives "+ q.measure()));
    }
}

The result of this is some output to the terminal, and a Window showing the Quantum Circuit you created:

qubit with probability on 1 = 0.4999999701976776, measured it gives 1
qubit with probability on 1 = 0.9999999403953552, measured it gives 1

(note that the first qubit can be measured as 0 or as 1)

Using maven

A typical pom.xml file looks as follows:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>org.redfx.javaqc</groupId>
  <artifactId>simplestrangedemo</artifactId>
  <packaging>jar</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>SimpleStrangeDemo</name>
  <url>http://maven.apache.org</url>

  <dependencies>
    <dependency>
      <groupId>org.redfx</groupId>
      <artifactId>strange</artifactId>
      <version>0.1.1</version>
    </dependency>
  </dependencies>
  <build> 
    <plugins>
      <plugin>
        <groupId>org.openjfx</groupId>
        <artifactId>javafx-maven-plugin</artifactId>
        <version>0.0.6</version>
        <configuration>
          <mainClass>SimpleStrangeDemo</mainClass>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

Using gradle

A typical build.gradle file looks as follows:

plugins {
    id 'application'
}

repositories {
    mavenCentral()
}

dependencies {
    implementation 'org.redfx:strange:0.1.1'
}

mainClassName = 'SimpleStrangeDemo'

About the sample application.

The code pasted above in the ShortStrangeDemo snippet is a short version of the code below. Both applications are similar, but the code below is more verbose which makes it easier to explain what is going on.

import org.redfx.strange.*;
import org.redfx.strange.gate.*;
import org.redfx.strange.local.SimpleQuantumExecutionEnvironment;
import java.util.Arrays;

public class SimpleStrangeDemo {

    public static void main(String[] args) {
        Program p = new Program(2);
        Gate xGate1 = new X(0); 
        Step step1 = new Step();
        step1.addGate(xGate1);
        p.addStep(step1);
        Gate hGate2 = new Hadamard(0);
        Gate xGate2 = new X(1);
        Step step2 = new Step();
        step2.addGates(hGate2, xGate2);
        p.addStep(step2);
        SimpleQuantumExecutionEnvironment sqee = new SimpleQuantumExecutionEnvironment();
        Result res = sqee.runProgram(p);
        Qubit[] qubits = res.getQubits();
        Arrays.asList(qubits).forEach(q -> System.out.println("qubit with probability on 1 = "+q.getProbability()+", measured it gives "+ q.measure()));
    }

}

This sample create a Program that requires 2 qubits. It will create 2 steps (s and t). The first step adds a Paul-X (NOT) Gate to the first qubit. The second steps adds a Hadamard Gate to the first qubit, and a NOT gate to the second qubit. Both steps are added to the Program.

In order to "run" this program, we need a QuantumExecutionEnvironment. Strange comes with a SimpleQuantumExecutionEnvironment which contains a very simple, non-optimized quantum computer simulator.

After running the program on this simulator, we inspect the state of the Qubits. As expected, there is a 50% chance the first qubit (which had an X and an H gate) will be in the 0 state, and a 50% chance it will be in the 1 state. The second qubit will always be in the 1 state.

Running this application a number of times will consistently give the same probabilities, and different measurements.

Visualization

The Strange API's allow creating and simulate quantum programs. A companion project, StrangeFX , allows visualising programs, and create them with a simple drag and drop interface. The sample program above rendered via StrangeFX looks as follows:

More samples

You can find more samples at https://github.com/johanvos/quantumjava