Abstract
The future quantum internet promises to create shared quantum entanglement between any two points on Earth, enabling applications such as provablysecure communication and connecting quantum computers. A popular method for distributing entanglement is by sending entangled photons through optical fiber. However, the probability of successful transmission decreases exponentially with the fiber length. This makes it challenging to realize large fiberbased quantum networks that create shared entanglement, let alone the construction of a quantum internet. Quantum repeaters have been proposed as a solution to mitigate losses by acting as intermediary nodes that divide long optical fibers into smaller segments. The required technology, however, is still under development. In this thesis we aim to expedite the realization of fiberbased quantum networks by identifying shortcuts towards that end.
One way in which we look for shortcuts is by identifying the technological advances that are required to build such networks. To achieve this we translate performance demands on the network to requirements on individual components, such as quantum repeaters. This way we are not only able to indicate how much development currentday technology still requires before functional quantum networks can be built, but also what specific set of improvements could be applied to stateoftheart hardware to get there as soon as possible.
A specific promising shortcut that we investigate in this thesis is the construction of quantum networks using existing fiber infrastructure. As deploying optical fiber is costly, an economical method for building quantum networks would be to incorporate fiber that has already been placed in the field. Existing infrastructure however imposes restrictions on quantum networks, in particular on the possible locations where quantum hardware could be installed. An important question to answer is then how severe the effects of these restrictions are. We address this question by investigating the performance degradation caused by displacing nodes from their optimal location, and the increase in required technological advances when restrictions are taken into account. Additionally, we provide tools for choosing where to deploy quantum repeaters when subject to placement restrictions.
Finally, we also address the fact that quantum networks may need to provide entanglement to more than just two parties. When a network has many end nodes that require bipartite entanglement between different pairs of them, it is important that it is designed such that every end node is sufficiently connected to every other end node. We provide conditions to judge whether this is the case and a method to ensure the conditions are met. Alternatively end nodes could require multipartite entangled states shared by more than two of them, in which case specialized nodes may need to be included in the network. We investigate what such a node could look like and perform a thorough performance analysis.
One way in which we look for shortcuts is by identifying the technological advances that are required to build such networks. To achieve this we translate performance demands on the network to requirements on individual components, such as quantum repeaters. This way we are not only able to indicate how much development currentday technology still requires before functional quantum networks can be built, but also what specific set of improvements could be applied to stateoftheart hardware to get there as soon as possible.
A specific promising shortcut that we investigate in this thesis is the construction of quantum networks using existing fiber infrastructure. As deploying optical fiber is costly, an economical method for building quantum networks would be to incorporate fiber that has already been placed in the field. Existing infrastructure however imposes restrictions on quantum networks, in particular on the possible locations where quantum hardware could be installed. An important question to answer is then how severe the effects of these restrictions are. We address this question by investigating the performance degradation caused by displacing nodes from their optimal location, and the increase in required technological advances when restrictions are taken into account. Additionally, we provide tools for choosing where to deploy quantum repeaters when subject to placement restrictions.
Finally, we also address the fact that quantum networks may need to provide entanglement to more than just two parties. When a network has many end nodes that require bipartite entanglement between different pairs of them, it is important that it is designed such that every end node is sufficiently connected to every other end node. We provide conditions to judge whether this is the case and a method to ensure the conditions are met. Alternatively end nodes could require multipartite entangled states shared by more than two of them, in which case specialized nodes may need to be included in the network. We investigate what such a node could look like and perform a thorough performance analysis.
Original language  English 

Qualification  Doctor of Philosophy 
Awarding Institution 

Supervisors/Advisors 

Award date  15 Jun 2023 
Print ISBNs  9789464832006 
DOIs  
Publication status  Published  2023 
Keywords
 quantum network
 quantum repeaters
 quantum repeater chains
 entanglement
 entanglement distribution
 quantum information