This conference presentation was prepared for the Quantum Technology: Driving Commercialisation of an Enabling Science III conference at SPIE Photonex, 2022.
This conference presentation was prepared for the Quantum Technology: Driving Commercialisation of an Enabling Science III conference at SPIE Photonex, 2022.
Future quantum networks will provide multi-node entanglement enabling secure quantum communication on a global scale. Traditional two-party quantum key distribution (2QKD) consumes pairwise entanglement which is costly in constrained networks. Quantum conference key agreement (QCKA) leverages multipartite entanglement within networks to directly produce identical keys among N users, providing up to N-1 rate advantage over 2QKD. In this contribution I will present work on the implementation of QCKA using photonic GHZ states distributed over telecom fibre of up to 50 km combined length. Furthermore, we implemented QCKA on a constrained network consisting of a 6-qubit photonic graph state on which we apply network coding routines to demonstrate the multi-partite advantage over the two-party paradigm.
Future quantum networks will provide multi-node entanglement enabling secure quantum communication on a global scale. Traditional two-party quantum key distribution (2QKD) consumes pairwise entanglement which is costly in constrained networks. Quantum conference key agreement (QCKA) leverages multipartite entanglement within networks to directly produce identical keys among N users, providing up to N-1 rate advantage over 2QKD. Here, we present a four-user QCKA protocol using photonic GHZ states distributed over fibre with combined lengths up to 50 km. Furthermore, we investigate a constrained network consisting of a 6-qubit photonic graph state which we apply network coding routines to distil suitable resource states.
A source of bright and pure single photons is an essential tool for photonic quantum technologies, predicted to enable secure communication and networking. Self-assembled quantum dots are among the leading candidates to realise such a source.
The currently highest-performing quantum dots emit at wavelengths unsuitable for fibre transmission, with telecom quantum dots lagging in performance. An intermediate step is to use quantum frequency conversion. Here we report to our knowledge the brightest quantum dot based source of telecom photons by frequency converting a near-infrared quantum dot embedded in a micropillar cavity to the telecom C-band.
In a single-photon BB84 protocol, this source is capable of producing asymptotic keys rates of 1 kbps at over 150 km of optical fibre.
Quantum key distribution is now a mature quantum communication protocol which allows the verifiably secure sharing of encryption keys between two communicating parties. It seeks to address potential vulnerabilities of data transmission and storage, offering a realistic possibility to share encryption keys which are robust to eavesdropping attacks and future-proof against hacking. Fibre-optic implementations of quantum key distribution currently have a limited practical transmission distance, of less than 400 km, making commercial applications limited. Quantum-specific amplifier/repeater technology is not yet mature enough to increase the transmission distance to achieve global capabilities. Optical fiber is also impractical and expensive for applications where a remote area or moving platform are involved.
In recent years, long-distance free-space quantum communications using low-Earth orbit satellites has seen an increase in interest from the academic community as well as from industrial organisations and national research institutes. The source of this new interest was a series of proof-of-principle demonstrations of satellite-based quantum key distribution in 2017. The use of free-space channels implementing airborne or satellite platforms also opens a range of new applications for quantum communications, as they allow coverage of remote areas, moving platforms, and also avoid the requirement of spooling fibre through volatile regions.
This presentation will give a general introduction to satellite-based quantum communications, an overview of the field, and discuss future endeavours. The talk will also include an overview of our research into novel photonic technology, such as the use of detector array technology, for the optical ground station receiver.
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