Research in quantum communication

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Chip with optomechanical crystals
A chip with optomechanical crystals is placed under the microscope in the Quantum Photonics Laboratory at Chalmers. The chip is to be used for conversion between microwave and optical quantum states. Photo: Anna-Lena Lundqvist

Quantum communication research within WACQT comprises a number of research groups that work with various aspects of quantum cryptography: quantum key distribution, entangled photon sources, increasing the transfer rate, etc. We are also involved in the National Quantum Communication Infrastructure in Sweden, which is part of the European Quantum Communication Infrastructure.

This page describes quantum communication research performed within WACQT. For a general introduction to quantum communication, please go to the page Quantum communication.

Coordinators of efforts in quantum communication:

Katia Gallo,, +46 76 517 33 15
Stefan Kröll,​. +46 46 222 96 26

Research projects in quantum communication

Integrated quantum pho​tonics

Hybrid quantum photonic c​ircuits
Nonlinearities at the single-photon level is crucial to reduce the resource overhead in quantum gates and teleportation. This project will demonstrate novel architectures for nonlinear interaction between photons, allowing to probe new regimes of light-matter interaction physics.
Principal investigator: Ali Elshaari, KTH
Postdoc: Jun Gao, KTH; PhD students: Govind Krishna and Zesheng Xu, KTH

Scalable quantum information processing using ultralow-loss silicon nitride nanophotonics
This project aims at attaining 15 dB two-mode squeezing on chip, scaling to 100 qumodes using quantum microcombs, and assessing a practical interface with programmable linear circuits.
Principal investigator: Victor Torres Company, Chalmers
PhD student: Sara Persia, Chalmers

High brightness entangled photon-pair sources in periodically poled LiNbO3-on-insulator
This project leverages the know-how on lithium niobate nanophotonics, periodic poling, and integrated nonlinear optics, with the aim to demonstrate a 10 MHz entangled-photon source based on spontaneous parametric downconversion at 1550 nm.
Principal investigator: Katia Gallo, KTH
PhD student: Tiantong Li, KTH

Sources of polarization-entangled photon pairs based on the nonlinearities of semiconductor nano-waveguides
The project’s aim is to develop laser-pumped arrays of nano-waveguide structures to provide polarization-entangled photons for use in systems for quantum key distribution.
Principal investigators: Marcin Swillo, KTH
PhD student: Albert Peralta Amores, KTH

Optical squeezing for quantum communication and sensing
The objective of the project is to generate optically squeezed light at 1550 nm, using lithium niobate-based guided wave sources to contribute both to quantum sensing and communication.
Principal investigator: Vaishali Adya, KTH
One PhD student and one postdoc position will be opened in 2024.

Quantum key distribution (QKD)

Quantum-dot based photon sources for the generation of highly indistinguishable and entangled photon pairs
The project focuses on generation of time-energy- and time-bin-entangled photon clusters that would enable the implementation of a quantum version of phase-shift keying. Such encoding is compatible with standard telecommunication fibre-optics network.
Principal investigator: Ana Predojević, Stockholm University
Postdoc: Laia Gines, Stockholm University

Multipartite photon entanglement in two-dimensional nonlinear lattices
The project aims at developing novel monolithic photon sources based on purely nonlinear photonic lattices in periodically poled materials to produce multiphoton entanglement and couple flying qubits at telecom wavelengths to stationary qubits in the near-infrared range.
Principal investigator: Katia Gallo, KTH
Postdoc: Hammad Anwer, KTH

Quantum communication based on few-mode and multi-core optical fibers
The main goal of this project is experimental demonstrations that high-dimensional photonic quantum systems (qudits) can be successfully generated and propagated over long distances in novel few-mode and multi-core fibres.
Principal investigator: Guilherme Xavier, Linköping University
PhD student: Alvaro Alarcón, Linköping University

Time-bin spatially-structured photonic qudits
This project studies the generation, transmission, and detection of spatially encoded states over few-mode fibres. The goal is to create a fully scalable method to increase the dimensionality of the photonic quantum systems by coherently combining time-bin encoding to the spatial photonic qudits.
Principal investigator: Guilherme Xavier, Linköping University
PhD student: Daniel Spegel-Lexne, Linköping University

Development of an entanglement-based, device independent quantum-key distribution system
The underlying idea is to use Bell tests to ensure that the encryption key is shared by only the legitimate receivers, even if the key generating device is made by an adverse, eavesdropping party. Learn more in this short film ​by Alban Seguinard.
Principal investigator: Mohamed Bourennane, Stockholm University
PhD student: Alban Seguinard, Stockholm University

Network quantum correlation
The project goal is to use novel aspects in the field of quantum communication and quantum networks and investigate the development of a prototype for long-distance quantum communication to a practical level suitable for deployment in industry.
Principal investigators: Mohamed Bourennane, Stockholm University and Michele Luvisotto, Hitachi Energy
Industrial PhD student: Emil Håkansson, Stockholm University/Hitachi Energy

Security-analysis toolbox for quantum cryptography
Quantum key distribution has an information-theoretically proven security principle, but in practice, one also needs to demonstrate the security of its implementation. The aim of this project is to investigate the security of practical quantum cryptography protocols.
Principal investigator: Mohamed Bourennane, Stockholm University
Postdoc: Piotr Mironowicz, Stockholm University

Metropolitan quantum network
This project will further develop polarisation-stabilisation schemes for deployed optical fibres and fabricate and implement a new generation of single- and entangled-photon sources based on quantum dots in positioned nanostructures. These devices will be used to operate the quantum network linking KTH to Ericsson and to implement quantum-communication protocols.
Principal investigator: Val Zwiller, KTH
PhD student: Stéphane Cohen, KTH

Robust and stable fiberized photon sources for QKD in telecom networks
In this project, we will develop, implement, and test several robust sources of entangled and single photons at telecom frequencies. We aim at developing and benchmarking stable and user-friendly sources that can be operated in a standard industrial environment and deployed in optical fibre networks to enable QKD.
Principal investigator: Val Zwiller, KTH
PhD student: Tanguy Schetelat, KTH

Microwave-to-optical transduction

Quantum microwave-nanophotonic transducer
This project develops transducers between microwave and optical quantum states. Such devices could be used to connect several superconducting quantum systems into a larger quantum processor. Read more
Principal investigator: Raphaël Van Laer, Chalmers
Involved PhD students: Johan Kolvik, Joey Frey, Paul Burger, and Trond Haug, Chalmers

Enhanced phonon-photon coupling with ferroelectric domain structures
The goal of this project is to develop models and simulations for the nonlinear optical, electrical, and mechanical response of ferroelectric domains and domain walls in periodically poled lithium niobate (PPLN) and its isomorphs. This theoretical groundwork will e.g. help us identify potential novel configurations for quantum acoustics and optics experiments in PPLN devices.
Principal investigator: Egor Babaev, KTH
PhD student: Anton Talkachov, KTH

National Quantum Communication Infrastructure in Sweden

The WACQT-led project National Quantum Communication Infrastructure in Sweden (NQCIS), which started in January 2023, is part of the European Quantum Communication Infrastructure, EuroQCI. NQCIS involves teams at KTH, Ericsson, Chalmers, Stockholm University, and Linköping University as well as emerging quantum companies in Sweden. It will build a multi-node testbed and deploy a national infrastructure for quantum key distribution, with metropolitan links in Stockholm and long-distance links between Stockholm and Linköping, tailored to the specific needs of public and industrial stakeholders in Sweden. Read more at the NQCIS website.