Secure Quantum Communications

A revolution is underway in communication: the laws of quantum physics can guarantee unconditional security in emerging quantum communication and cryptography systems. CQC2T will partner with industrial companies to address the key challenge of increasing the bit-rate and range of these communication channels to move secure communication to the national, and eventually global scale. The secure quantum communication program will equip Australian government and industry with a suite of quantum communication technologies enabling complete security against eavesdropping, and laying the groundwork for distributed quantum computing.

Cryptography is a tool that enables the secure transmission of a secret message between a sender and a recipient from any potential eavesdropper. Traditionally the sender is called Alice, the recipient Bob, and the eavesdropper Eve. Quantum cryptography is a particular form of cryptography that relies on the laws of quantum mechanics in order to ensure unconditional security. Traditional forms of cryptography, which are of everyday use, either rely on a public key that everybody can access or on a private key.


Public key cryptography is widely used for example by banks to perform secure money transfer, or over the Internet for securing websites access. The security of public key cryptography relies on the difficulty to realise an efficient algorithm to “crack” the communication. However these protocols are not unconditionally secure because no mathematical theorem forbids Eve to build a clever revolutionary algorithm, or a quantum computer, that will allow her to crack such codes.

On the other hand, private key cryptography can be unconditionally secure if encryption techniques such as the ‘one time pad’ are performed. The weakness of these techniques is that the key has to be securely transmitted by Alice to Bob, whilst at the same time they are using cryptography because they cannot rely on their classical transmission channels.

Quantum cryptography elegantly solves this dilemma by enabling the unconditionally secure transmission of a random binary key between Alice and Bob, and hence is very often referenced as Quantum Key Distribution (QKD). Basically, the security of the transmission is ensured by the no-cloning theorem that forbids the perfect reproduction, or cloning, of a quantum system without disturbing it, therefore enabling Alice and Bob to detect the presence of a potential eavesdropper.


Bennett and Brassard proposed in 1984 and demonstrated in 1992 the first discrete variable (DV) quantum cryptography protocol known as BB84. DV-QKD is still the subject of successful ongoing, however, new approaches are being considered in order to make quantum cryptography feasible with bright light sources. The later are known as Continuous Variable (CV) and are motivated by the availability of efficient detectors, and the maturity of bright light sources compatible with the present optical communication systems operating at very high rates.

The main goal of this program is to demonstrate Quantum Cryptography in the Australian Parliamentary Triangle. In close partnership with QuintessenceLabs and Lockheed Martin Australia, CQC2T will implement the Government Quantum Network (GQN). This is an initiative of multiple governmental agencies to provide the highest level of information security for intra-governmental communications in Canberra. In order to achieve this goal, the secure quantum communication program is developing a post-selection based continuous variables quantum key distribution device. We concentrate on all the aspects of such a device, from the physical optical implementation, theoretical modeling, and underlying analog and digital electronics, to the information processing algorithm and integration into existing telecommunication networks. In parallel with the first field trial in Australia, we will develop industrial standards in tandem with the European Telecommunications Standard Institute and the Australian Department of Defence.