Multi-Partite Quantum Communication with Squeezed Light

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Tobias Gehring


Technical University of Denmark


DKK 4,999,283




Semper Ardens: Accelerate


Quantum communication protocols use fundamental properties of quantum physics to distribute cryptographic keys between parties for unbreakable data encryption. The laws of quantum physics thereby ensure that security cannot be broken, neither by quantum computers nor by technical innovations. Usually quantum communication is performed between only two parties. In the project we will extend this to three and more parties by developing new protocols and experimentally demonstrating them in the lab.


Quantum communication between two parties is well established and first commercial solutions are on the market. Multi-partite quantum communication, is however not well studied so far and it requires the development of novel protocols and experimental techniques which is what we aim for in the project. In the long run those protocols will play an important role in the research and development of the quantum internet, a network of quantum nodes spanning the world which connect quantum computers and which can be used to perform quantum cryptography.


We will implement quantum communication using quantum states encoded in the in-phase and quadrature components of light. Light is the perfect medium for quantum communication as it can be transmitted through optical fibers with low optical loss so that the parties involved in the communication can be distributed across for instance a city. In the project we will use squeezed states of light. Squeezed states have the exciting property that their fundamental quantum noise is lower than the fundamental quantum noise of a regular laser. This extraordinary property will make it possible to achieve quantum communication between multiple parties.

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