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#4 in Simulation

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Latest version Documentation License

A sans-io Rust implementation of the CQC interface.

The Classical-Quantum Combiner (CQC) interface is used to program quantum networking nodes to create, transmit, and manipulate qubits.

The CQC interface will be used to interact with the Dutch demonstration network, currently under development at QuTech in the Netherlands. At present, the CQC interface is supported only by the quantum network simulator Simulaqron.

Principle of Operation

This library provides two functions:

  1. Build valid CQC packets.

  2. Encode/decode to/from binary format. It is left to the user to decide how best to fit I/O in their framework.

Building Packets

This crate offers two ways of building packets

  1. Manually - one can manually build packets using the header definitions and documentation provided in the hdr module.

  2. Using the builder module - the builder module provides a simple API for generating CQC packets. It should be used in conjunction with the CQC interface documentation in the hdr module.

Encoding/decoding packets

All headers in the hdr module implement serde's Serialize and Deserialize traits which mean they can be directly used as input to bincode. The Encoder and Decoder impls provide an example.

The builder module returns a Request struct which implements Serialize which can be used with bincode.

The library provides a Response struct which implements Deserialize and can be used to deserialize any response from the SimulaQron server.

CQC in action

The following example will create a qubit on one node and send it to another node. Before running the example below start up the SimulaQron nodes with $NETSIM/run/startAll.sh --nrnodes 2.

extern crate bincode;
extern crate cqc;

use cqc::builder;
use cqc::hdr;
use std::net;

fn main() {
    // Initialise local node `localhost:8803`.
    let hostname = String::from("localhost");
    let local_port: u16 = 8803;

    // Set up remote node ``.
    let remote_host: u32 = u32::from(net::Ipv4Addr::new(127, 0, 0, 1));
    let remote_port: u16 = 8804;

    // Initialise application state with ID 10.
    let app_id: u16 = 10;
    let builder = builder::Builder::new(app_id);
    let mut coder = bincode::config();

    // Create, and send a qubit from `localhost:8803` to `localhost:8804`.
        // Open connection to local node.
        let stream = net::TcpStream::connect((hostname.as_str(), local_port))
            .expect("Connect failed");

        // Create the qubit.
        let request = builder.cmd_new(0, hdr::CmdOpt::empty());
        coder.serialize_into(&stream, &request).expect(
            "Sending failed",

        // Wait for confirmation of creation.
        let response: cqc::Response = coder.deserialize_from(&stream).expect("Receive failed");

        // Read the created qubit ID.
        let note = response.notify.get_notify_hdr();
        let qubit_id = note.qubit_id;

        // Send the qubit to the remote node.
        let request = builder.cmd_send(
            builder::RemoteId {
                remote_app_id: app_id,
                remote_node: remote_host,
                remote_port: remote_port,
        coder.serialize_into(&stream, &request).expect(
            "Sending failed",

        // Wait for confirmation.
        let response: cqc::Response = coder.deserialize_from(&stream).expect("Receive failed");
        assert!(response.cqc_hdr.msg_type.is_done(), "Unexpected response");

    // Receive the qubit on the remote node, `localhost:8804`.
        // Open connection to local node.
        let stream = net::TcpStream::connect((hostname.as_str(), remote_port))
            .expect("Connect failed");

        // Send a request to receive a qubit.
        let request = builder.cmd_recv(0, hdr::CmdOpt::empty());
        coder.serialize_into(&stream, &request).expect(
            "Sending failed",

        // Receive a response.
        let response: cqc::Response = coder.deserialize_from(&stream).expect("Receive failed");
        assert!(response.cqc_hdr.msg_type.is_recv(), "Unexpected response");
        let note = response.notify.get_notify_hdr();
        let qubit_id = note.qubit_id;

        println!("Received qubit ID: {}", qubit_id);

Design goals

The following goals drive the design of the cqc crate:

  • The user should be able to create any valid packet

    This goal is achieved by having correct struct definitions for the different CQC headers.

  • It should be difficult, though preferably impossible, to create invalid packets

    The second goal is achieved by using Rust's typing system as much as possible, especially enums for fields with only a small set of possible values. Furthermore a builder module is provided which guarantees correct CQC packets.

  • Decoding should raise errors if unrecognised values are detected

    This is achieved through a combination of type definitions and deserialization implementations.

  • No assumption about the user's run-time should be made

    The library is sans-io and only provides a very plain encoder and decoder as an example. The intention is that the user builds packets using the cqc library, but I/O is their responsibility. The Serialize and Deserialize traits are implemented so that the user can simply use bincode for encode/decode.


  • Factory, Mix, If, InfTime Headers are not currently fully supported.


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