My research can be divided roughly into two topics, so the publications are listed separately under these two. These two topics are Anonymous communication in quantum networks, and (Multi-partite) entanglement in networks and graph states.
Anonymous communication in quantum networks
Anonymous communication conveys the idea that people may wish to send messages over a network, without Usually, anonymity is considered in conjuction with secret communication, which hides the contents of the message itself. Secret communication is facilitated by encryption; anonymous and secret communication therefore needs anonymous encryption. The generalisation of this to more than one sender and one receiver is called anonymous conference key agreement (ACKA) - much of my research has explored ACKA, ranging from the first proof of concept to more mature protocols in various settings, as well as experimental implementations and showcases.
More recently, we have also considered anonymity in other networking tasks. More specifically, we have been exploring anonymous private parameter estimation, where a network of quantum sensors holding a parameter can establish their average, without having to give up any information about the individual parameters, nor the indentities of the nodes in the network.
1. Anonymous Conference Key Agreement (arxiv, Published)
Hahn, de Jong, Pappa - Anonymous Conference Key Agreement. PRX Quantum 1, 020325 (2020).
- The first proof of concept for anonymous conference key agreement (ACKA) in quantum networks.
2. Anonymous and secret communications in quantum networks (arxiv, Published)
Thalacker, Hahn, de Jong, Pappa, Barz - New J. Phys. 23 083026 (2021).
- Experimental realization of the first ACKA protocol.
3. Secure Anonymous Conferencing in Quantum Networks (arxiv, Published)
Grasselli, Murta, de Jong, Hahn, Bruß, Kampermann, Pappa - PRX Quantum 3, 040306 (2022).
- An improved ACKA protocol that is both robust and more secure. Includes finite key analysis and simulations.
4. Anonymous conference key agreement in linear quantum networks (arxiv, Published)
de Jong, Hahn, Eisert, Walk, Pappa - Quantum 7, 1117 (2023).
- An ACKA protocol that uses linear networks, which are much easier to realize than the central networks of the previous protocols.
5. Experimental ACKA using linear cluster states (arxiv, Published)
Rückle, Budde, de Jong, Hahn, Pappa, Barz - Phys. Rev. Research 5, 033222 (2023).
- Experimental realization of the ACKA protocol in linear networks.
Entanglement in networks and graph states
Entanglement is one of the most fundamental concepts in quantum information science, and is the cornerstone in moest applications in quantum computing, communication and cryptography. Roughly speaking, two or more quantum systems are said the be entangled if their states cannot be separately described anymore, but only as a whole. Originally only bi-partite entanglement was considered, but the last two decades has seen an incresing interest in multi-partite entanglement, that consideres more than two quantum systems. An indispensible tool in the study of multi-partite entanglement is the graph state, a particular type of multi-partite entangled state that conveys many of their interesting properties, while also having a clear graphical representation. My research in multi-partite entanglement has particularly focussed on the equivalence of different forms of multi-partite entanglement in quantum networks, that due to their distributed nature have a reduced power in manipulating and treating quantum states.
1. Extracting GHZ states from linear cluster states (arxiv, Published)
de Jong, Hahn, Tcholtchev, Hauswirth, Pappa - Phys. Rev. Research 6, 013330 (2023).
- A complete characterization of how GHZ states can be realized from linear cluster states in quantum networks.
2. Distinguishing graph states by the properties of their marginals (arxiv)
Vandré*, de Jong*, Hahn, Burchardt, Gühne, Pappa - arxiv preprint. * these authors have contributed equally.
- A study on how to detect distinguish different forms of entanglement in quantum networks by using the properties of reduced states.