The worldwide race to the quantum computer is in full swing. This computer can take on computing tasks that we can only dream of today, such as finding proteins that can be used as medicines in seconds flat. Leiden physicists have discovered how the Majorana particle can be used as a building block…

This thesis covers several aspects of quantum algorithms for near-term quantum computers and its applications to quantum chemistry and material science.

This thesis is a collection of theoretical works aiming at adjusting quantum algorithms to the hardware of quantum computers.

The NEASQC project brings together academic experts and industrial end-users to investigate and develop a new breed of Quantum-enabled applications that can take advantage of NISQ (Noise Intermediate-Scale Quantum) systems in the near future. NEASQC is use-case driven, addressing practical problems…

This thesis covers various applications of topology in condensed matter physics and quantum information.

Promotor: C.W.J. Beenakker, Co-Promotor: A.R. Akhmerov

Machine learning - on classical computers- has made great progress in the past five years. Computer translation of speech and text is just one example. In Leiden, some researchers expect that machine learning, empowered by quantum systems, even if they only contain a few dozen qubits, can lead to a…

This thesis probes under what conditions quantum computing presents an advantage over classical computing.

Quantum annealing belongs to a family of quantum optimization algorithms designed to solve combinatorial optimization problems using programmable quantum hardware. In this thesis, various methods are developed and tested to understand how to formulate combinatorial optimization problems for quantum…

Top scientists of three Dutch universities are working on software and systems for quantum computers. Researchers of the Leiden Institute of Advanced Computer Science (LIACS) and the Leiden Institute of Physics (LION) are developing new algorithms to make those super computers work. The coming years,…

Can we use quantum computers in a way that is also relevant to society? With the help of a 2-million-euro NWA grant, Leiden University will work with partners such as Surf, Google and Volkswagen to demonstrate that quantum computers are also of value outside the lab.

The aim of this thesis is to present novel techniques for proving cryptographic schemes secure against quantum adversaries. Most results are within the context of an idealized model called the ‘quantum random-oracle model’.

The 18.8 million euro NWO Zwaartekracht grant for quantum software which Amsterdam, Delft and Leiden landed collectively, means for Leiden University among others the appointment of two new permanent scientific staff members, who will each form their own research group, divided among Computer Science,…

Physicist Martin van Exter works with light at nanoscale, at the forefront of nanocomputer research. But as Director of Education he also has a vision for physics teaching. Inaugural lecture 18 November.

Quantum computing is an emerging technology, which holds the potential to simulate complex quantum systems beyond the reach of classical numerical methods.Despite recent formidable advancements in quantum hardware, constructing a quantum computer capable of performing useful calculations remains challenging.In…

This thesis investigates the contribution of quantum computers to machine learning, a field called Quantum Machine Learning. Quantum Machine Learning promises innovative perspectives and methods for solving complex problems in machine learning, leveraging the unique capabilities of quantum computers…

In this work we describe three methods to improve the performance of Quantum Field Theory calculations.

This thesis addresses questions on effectively using variational quantum circuits for machine learning tasks.

Research groups in the Quantum Matter & Optics programme investigate electronic properties of matter and light-matter interactions with emphasis on quantum information.

Pushing the boundaries of quantum theories – that’s exactly what the physicists at Leiden University excel at. Researchers in Leiden are launching eight new quantum research projects as part of the Quantum Limits consortium.

Quantum computers are a proposed fundamentally new type of computer. They aim to perform some computations much faster than previously possible by exploiting phenomena at the quantum scale, called superposition and entanglement.

Quantum hardware comes with a different computing paradigm and new ways to tackle applications. Much effort has to be put into understanding how to leverage this technology to give real-world advantages in areas of interest for industries such as combinatorial optimization or machine learning.

Leiden physicist Julia Cramer receives 50 thousand euros in funding for 'Let's talk about quantum', a research project on communication about quantum computing. A project for high school students by education expert Henk Buisman is also included in the NEWA ELSA funding.

With the help of quantum mechanics, digital quantum hardware may be able to tackle some of the problems that are too difficult for ordinary computers. But despite these expectations and the ongoing effort of the research community, reliable quantum computers are not yet realized in a lab setting.

The standard approach to build a quantum computer with Majoranas as building blocks is to convert them into qubits. However, a promising application of quantum computing—quantum chemistry—would require these qubits to be converted again into so-called fermions. Physicists from Leiden and Delft suggest…

The race to build the first quantum computer is still ongoing, but Morten Bakker has made big step forward in that process with qubits. A qubit is a unit of quantum information that can be produced in large numbers on chips. Qubits capable of exchanging photons (light particles) could be used in the…

With defending his thesis ‘Applications of topology to Weyl semimetals and quantum computing’, the Leiden theoretical physicist Tom O'Brien has gained the rare 'cum laude' qualification. The freshly minted PhD has started a five year research programme on quantum algorithms for quantum chemistry, funded…

A single self-assembled semiconductor quantum dot in a high-finesse optical microcavity - the subject of this thesis - is an interesting quantum-mechanical system for future quantum applications. For instance, this system allows trapping of an extra electron and thus can serve as a spin quantum memory,…

The Divide & Quantum (D&Q) project offers various solutions to harness the power of quantum computers in the near term, proposing entire pipelines, from theoretical research, via implementation to real-world case studies in a number of disciplines, to science communication with the broader society.…

American physicist and quantum computing pioneer Seth Lloyd is the 65th Lorentz professor. He will deliver the Ehrenfest lecture on 5 June, and several more lectures on quantum computing on 11, 18 and 25 June.

Quantum computing is a novel paradigm for computation, which is nearing real-world impact with the coming generation of limited, but nonetheless powerful quantum devices.

The worldwide race to the quantum computer is in full swing. This computer can bring about a breakthrough in discovering medicines and new materials. Leiden researchers, together with the TU Delft, are taking part in the race. There is now a dossier online about their work.

Most of current public-key cryptography is considered insecure against attacks from sufficiently powerful quantum computers. Post-quantum cryptography studies methods to secure information resistant against such attacks. One proposal is isogeny-based cryptography, which bases its security on computational…

The quantum nature of matter and light has grown into a broad and fruitful research field for theorists and experimentalists alike. It combines foundational research with toward applications, the most well known of which is the quantum computer.

Quantum computers deserve their own quantum internet. This is a network that dispatches information not in the form of bits - ones and zeros - but rather as qubits, just like in the quantum computer itself. In the view of Dirk Bouwmeester, a professor in Leiden’s Quantum Matter & Optics research group,…

Quantum Delta NL, a research programme in which Leiden University participates, has been awarded 615 million euros from the National Growth Fund to help develop the Netherlands into a top player in quantum technology.

Why do black holes emit thermal radiation? And how does a closed quantum system thermalize?

The quantum nature of matter and light has grown into a broad and fruitful research field for theorists and experimentalists alike. It combines foundational research with toward applications, the most well known of which is the quantum computer.

Quantum Information Science & Technology (QIST) encompasses the understanding, design, construction and investigation of quantum information processing systems, such as quantum computers, quantum communication networks, and quantum sensors.

Born in Europe roughly 100 years ago, quantum physics brought forth a veritable technological revolution through semiconductors, lasers, fibre optics, and many other technologies that are today ubiquitous in our lives. Now, during the second quantum revolution, Europe can take the lead once more in…

Thermodynamics is one of the founding scientific pillars that has helped us better understand heat engines, biology, ecosystems, and even black holes. While it fundamentally describes large systems by examining the bulk behavior of their constituents, it is anchored in the statistical equivalence of…

In my research, we developed a method to distinguish knots. A knot is a mathematical depiction of the everyday knot that occurs in ropes and cords.

Optical cavities are useful tools to enhance the interaction between light and matter, which is important to make good quantum emitters. However, it turns out that the cavities themselves (without any quantum emitters) are already interesting objects to study.