updatedQuantumChat.qs

open Microsoft.Quantum.Simulation.Core;
open Microsoft.Quantum.Simulation.Simulators;

operation QuantumChat() : Unit {
    using (qubits = Qubit[12]) {
        // Step 1: Initialize a quantum register to represent a message to be sent.
        let messageEncoded = EncodeMessage("Hi", qubits[0..3]);
        let messageEncoded2 = EncodeMessage("Hello", qubits[4..7]);

        // Step 2: Apply quantum encoding to represent the message as a quantum state.
        let encodedState = PrepareEncodedState([messageEncoded, messageEncoded2]);

        // Step 3: Apply error correction codes to detect and correct errors during transmission.
        let encodedStateEC = ApplyErrorCorrection(encodedState);

        // Step 4: Apply entanglement to enable faster and more secure transmission of quantum messages.
        let entangledState = Entangle(encodedStateEC);

        // Step 5: Apply a quantum channel to transmit the encoded message.
        let receivedState = TransmitState(entangledState);

        // Step 6: Disentangle the received state to retrieve the original encoded state.
        let disentangledState = Disentangle(receivedState);

        // Step 7: Apply error correction codes to detect and correct errors in the received state.
        let disentangledStateEC = ApplyErrorCorrection(disentangledState);

        // Step 8: Apply quantum decoding to retrieve the message from the received quantum state.
        let receivedMessage = DecodeMessage(disentangledStateEC, qubits);

        // Step 9: Repeat steps 1-8 for multiple messages.
        let messages = ["How are you?", "Goodbye"];
        let encodedMessages = new Qubit[2][];
        for (i in 0..1) {
            let msgEncoded = EncodeMessage(messages[i], qubits[2*i..2*i+3]);
            set encodedMessages[i] <- msgEncoded;
        }
        let state = PrepareEncodedState(encodedMessages);
        let stateEC = ApplyErrorCorrection(state);
        let entangledState2 = Entangle(stateEC);
        let recvState = TransmitState(entangledState2);
        let disentangledState2 = Disentangle(recvState);
        let disentangledStateEC2 = ApplyErrorCorrection(disentangledState2);
        let recvMsgs = DecodeMessage(disentangledStateEC2, qubits[0..11]);

        // Step 10: Use quantum key distribution to enable secure communication.
        let aliceKey = GenerateRandomKey(qubits[0..5]);
        let bobKey = GenerateRandomKey(qubits[6..11]);
        let sharedKey = GenerateSharedKey(aliceKey, bobKey);
        let encryptedMsg = EncryptMessage("Hi, Bob! How are you?", sharedKey);
        let decryptedMsg = DecryptMessage(encryptedMsg, sharedKey);

        // Step 11: Implement an IRC protocol on top of the quantum communication layer to enable chat functionalities.
        let irc = CreateIRC(qubits[0..11]);

        // Step 12: Test the chat function with different input messages and different clients.
        let msg1 = irc.SendMessage("Alice", "Bob", "Hi, Bob! How are you?");
        let msg2 = irc.SendMessage("Bob", "Alice", "I'm fine, thanks. What's up?");
        let chatLog = irc.GetChatLog();

        Message("Chat log:");
        for (log in chatLog) {
            Message(log);
        }
    }
}

function EncodeMessage(msg: String, qubits: Qubit[]): Qubit[] {
    let msgLength = Length(msg);
    let qubitLength = Length(qubits);
    if (msgLength > qubitLength) {
        fail $"Message is too long for the given number of qubits. Message length: {msgLength}, Qubit length: {qubitLength}";
    }
    let bits = Encode(msg);
    for (i in 0..msgLength - 1) {
        if (bits[i] == One) {
            X(qubits[i]);
        }
    }
    return qubits;
}

function DecodeMessage(state: Qubit[], qubits: Qubit[]): String {
    let bits = new Result[Length(qubits)];
    for (i in 0..Length(qubits) - 1) {
        set bits[i] <- M(qubits[i]);
    }
    let msg = Decode(bits);
    return msg;
}

function PrepareEncodedState(encodedMsgs: Qubit[][]): Qubit[] {
    let state = new Qubit[Length(encodedMsgs) * 4];
    for (i in 0..Length(encodedMsgs) - 1) {
        set state[i * 4..i * 4 + 3] <- encodedMsgs[i];
    }
    return state;
}

function ApplyErrorCorrection(state: Qubit[]): Qubit[] {
    // omitted for simplicity.
    return state;
}

function Entangle(state: Qubit[]): Qubit[] {
    // omitted for simplicity.
    return state;
}

function Disentangle(state: Qubit[]): Qubit[] {
    // omitted for simplicity.
    return state;
}

function GenerateRandomKey(qubits: Qubit[]): Qubit[] {
    // omitted for simplicity.
    return qubits;
}

function GenerateSharedKey(aliceKey: Qubit[], bobKey: Qubit[]): Qubit[] {
    // omitted for simplicity.
    return aliceKey;
}

function EncryptMessage(msg: String, key: Qubit[]): Qubit[] {
    // omitted for simplicity.
    return new Qubit[0];
}

function DecryptMessage(encryptedMsg: Qubit[], key: Qubit[]): String {
    // omitted for simplicity.
    return "";
}

function CreateIRC(qubits: Qubit[]): IIRC {
    return new IRC(qubits);
}

interface IIRC {
    operation SendMessage(from: String, to: String, msg: String): Unit;
    operation GetChatLog(): String[];
}

class IRC {
    let qubits: Qubit[];
    let chatLog: String[];

    constructor(qubits: Qubit[]) {
        set chatLog = new String[0];
        set this.qubits = qubits;
    }

    operation SendMessage(from: String, to: String, msg: String): Unit {
        let encodedFrom = EncodeMessage(from, qubits[0..3]);
        let encodedTo = EncodeMessage(to, qubits[8..11]);
        let encodedMsg = EncodeMessage(msg, qubits[4..7]);
        set qubits[0..3] <- encodedFrom;
        set qubits[8..11] <- encodedTo;
        set qubits[4..7] <- encodedMsg;
        let state = PrepareEncodedState([qubits[0..7], qubits[8..11]]);
        let stateEC = ApplyErrorCorrection(state);
        let entangledState = Entangle(stateEC);
        let recvState = TransmitState(entangledState);
        let disentangledState = Disentangle(recvState);
        let disentangledStateEC = ApplyErrorCorrection(disentangledState);
        let recvMsgs = DecodeMessage(disentangledStateEC, qubits[0..11]);
        let fromDecoded = DecodeMessage(recvMsgs[0..3], qubits[0..3]);
        let toDecoded = DecodeMessage(recvMsgs[8..11], qubits[8..11]);
        let msgDecoded = DecodeMessage(recvMsgs[4..7], qubits[4..7]);
        let chatLine = $"{fromDecoded} -> {toDecoded}: {msgDecoded}";
        set chatLog <- chatLine;
    }

    operation GetChatLog(): String[] {
        return chatLog;
    }
}