Hardware and Protocol Optimization in Quantum-Repeater Networks

The future quantum internet promises to enable users all around the world to, among other applications, generate shared secure keys and perform distributed quantum computations. To do so, entanglement must be distributed between remote users. One way of doing this is by sending photons through optical fiber, which allows for reusing some...

Software Abstractions for Programmable Quantum Network Nodes

Computer networks have been one of the most revolutionary concepts and technologies of the last fifty years. Currently, it is arguably impossible to imagine a world without the internet. And yet, just five decades ago, hardly anybody knew what it even meant. Today, the first quantum computer networks are starting to take shape, along with the...

Shortcuts towards fiber-based quantum networks

The future quantum internet promises to create shared quantum entanglement between any two points on Earth, enabling applications such as provably-secure communication and connecting quantum computers. A popular method for distributing entanglement is by sending entangled photons through optical fiber. However, the probability of successful...

Quantum Networks using Spins in Diamond

A future quantum internet will bring revolutionary opportunities. In a quantum internet, information will be represented using qubits. These qubits obey the rules of quantum mechanics. The possibilities to create superposition and entangled states, and to perform projective measurements give the quantum internet its unique strengths. A...

Distributing entanglement in quantum networks

The research presented in this thesis focused on the problem of entanglement distribution. Simply put, the two main problems facing (practical) implementation of entanglement distribution over quantum networks are loss and noise. Quantum repeaters are meant to overcome the effects of loss, but in practice their implementation always comes at the...

Multi-Node Quantum Networks with Diamond Qubits

The Internet has revolutionized the way we live. It has enabled applications far beyond what it was originally built for, and it will continue to exceed our expectations for the future. Quantum computers, and the network that will connect them—the Quantum Internet— are likely going to follow the same path. Differently from normal computers,...

Tools for the design of quantum repeater networks

Communication between remote quantum computers enables tasks that are unachievable with their conventional counterparts, such as unconditionally-secure communication or quantum computing in the cloud. Bridging long distances, where the communication fundamentally suffers from loss, can be achieved by splitting up the distance into segments and...

Entanglement Generation in Quantum Networks: Towards a universal and scalable quantum internet

Quantum mechanics shows that if one is able to generate and manipulate entanglement over a distance, one is able to perform certain tasks which are impossible using only classical communication. Classical communication refers to what is used in the Internet of today. A quantum internet would therefore bring new capabilities to our highly...

Quantum resource-saving protocols for early quantum networks

The Internet as we know it has had an immense impact on the way we communicate. We can now do it faster and more securely than ever before. Enabling quantum communication between any two points on Earth is the next step towards even more secure communication. This is the goal of the quantum internet. Although it is hard to predict all of the...

Theoretical advances in practical quantum cryptography

Most of themainstream cryptographic protocols that are used today rely on the assumption that the adversary has limited computational power, and that a given set of mathematical problems is hard to solve (on average), i.e. that there is no polynomial time algorithm that solves these problems. While these assumptions are reasonable for now they...

Building blocks of quantum repeater networks

Quantum information in the real world: Diagnosing and correcting errors in practical quantum devices

Quantum computers promise to be a revolutionary new technology. However, in order to realise this promise many hurdles must first be overcome. In this thesis we investigate two such hurdles: the presence of noise in quantum computers and limitations on the connectivity and control in large scale quantum computing architectures.In order to combat...

A theory of thermodynamics for nanoscale quantum systems

Thermodynamics is one of the main pillars of theoretical physics, and it has a special appeal of having wide applicability to a large variety of different physical systems. However, many assumptions in thermodynamics apply only to systems which are bulk material, i.e. consisting a large number of microscopic classical particles. Due to the...