Quantum Computing

Quantum computing exploits the principles of quantum mechanics, creating systems that can perform calculations far beyond the capabilities of even the most powerful classical computers. 

UCL Computer Science has played a vital role in building the theoretical foundations of the field. Our academics, students and alumni have contributed landmark advances – from Toby Cubitt’s quantum-computing-based proof of the undecidability of the spectral gap problem, one of the most important challenges in theoretical physics, to Lluis Masanes’ first general security proof for device-independent quantum cryptography. 

Former postdoctoral researcher Nikolas Breuckmann also achieved a breakthrough with his proof of the NLTS conjecture, a famous open problem in quantum information theory.

Each of these theoretical breakthroughs has helped to bring us to the threshold of a new era of quantum technologies, with the possibility for transformative applications in areas such as materials science and chemistry.  

What kinds of quantum computing research are we working on at UCL Computer Science? 

Quantum computing and algorithms 

There are computational problems so difficult that they could never be solved on a classical computer. Quantum computing provides new ways to approach these problems – and quantum algorithms are the key to unlocking that power. 

Our quantum computing researchers are shedding new light on the underpinning theory of quantum computation and quantum complexity theory. These advances in theoretical understanding allow our academics and spinout companies to explore potential algorithmic applications in materials modelling.  

Quantum algorithms could eventually give us revolutionary new battery and solar energy technology, and unlock high-performance catalyst optimisation techniques for new chemical processes across many industries. 

Quantum cryptography and communication 

Quantum cryptography is one of the original pillars of quantum technology, with profound implications for information security. Because quantum computing processes information in novel ways that are impossible with classical means, our current private communication systems are vulnerable against large-scale quantum computers. However, quantum technology also offers a secure alternative. 

Our work in this area includes both theoretical and applied research, including projects with industry partners to develop key distribution systems, as well as random number generators for a wide range of applications. 

Quantum simulation  

Quantum simulation harnesses the power of quantum computers to simulate physical systems at the quantum level. Modelling processes and interactions between large numbers of quantum particles gives us a greater understanding of chemical reactions or the properties of materials.  

Being able to test materials design and chemical processes in simulation could revolutionise materials discovery and computational chemistry – bringing us closer to achieving our crucial sustainable development goals. 

Quantum many-body physics  

The field of quantum computing was developed by applying quantum mechanics to computer science. Now, we’re establishing a two-way flow between the disciplines, exploiting ideas and results from theoretical computer science to address problems and answer questions in theoretical physics. 

At UCL Computer Science, we are using complexity theory to understand the physics of quantum spin systems, and to construct models representing new phases of matter. We also use quantum circuits to model and characterise a wide range of physical phenomena, from phase transitions to quantum gravity. 
 

Associated research groups and centres