Far From Equilibrium Quantum Simulators

This is an extension of the Fellowship "Coherent quantum matter out of equilibrium - from fundamental physics towards applications".

The original project concerned collective phenomena in a wide range of photonic systems to explore the fundamental properties of matter and their use for device applications. The extension will now focus on systems of strongly interacting and massive photons, placed in artificially made lattice potentials mimicking real solids, and their use as quantum simulators.

Ever since the idea of quantum simulations, which involves the creation and control of simpler systems to model the behaviour of more complex and poorly understood systems, have been proposed, the search for suitable physical platforms has been one of the most active branches of Quantum Technologies. Due to their light mass, photons have been shown to exhibit quantum effects at high, up-to-room temperatures and can be easily integrated with other platforms for technological applications. Thus, the idea of creating synthetic quantum matter out of photons to simulate poorly understood lattice systems, such as real solids, has been particularly attractive. However, photons cannot be perfectly trapped and decoupled from their environment, which leads to non-equilibrium dissipative conditions, that are challenging to describe if combined with strong interactions and correlations, but particularly relevant for real life applications.

The main aim of the project is to devise effective new theoretical and computational methods to treat strong correlations and entanglement in driven-dissipative lattice systems of photons in collaboration with experimental groups, and to use these methods to design protocols for experimental exploration of those in the spirit of quantum simulation. We will focus on two particularly promising platforms: polariton lattices i.e. specially engineered semiconductor structures, and superconducting circuits coupled to microwave photons. Our research will address fundamental problems of phase transitions, orders, symmetry and topology when strong interactions combine with strong dissipation and non-equilibrium conditions, as well as practical questions how correlations form and propagate, and how they can be controlled and protected from the destructive influence of the outside world.

Who will benefit from this research?

There are four classes of beneficiaries:
1) high-tech industry;
2) general public (science minded pupils, students, people interested in basic knowledge);
3) PDRAs and UCL students;
4) other academics in the PI's and other research areas.

How might they benefit from this research?

Class 1) The potential impact of our research is in the future application of quantum simulators in solving complex problems from a wide spectrum of fields. Driven-dissipative platforms, such as polariton and circuit QED lattices, are especially relevant as most real systems are open and to some degree coupled to their environments. In particular, semiconductor microcavities are unique in allowing observation of quantum effects at up to room temperature. One of the key features of this platform is its high degree of integration in micrometre size semiconductor chips. It operates at optical frequencies where a wide variety of laser sources and the best detectors for quantum measurements are available. Thanks to this photonic component it could potentially be integrated easily with other platforms. At the same time, one of the main motivations for constructing and exploring superconducting qubits comes from their potential application as future computational elements.

Class 2) The project is concerned with fundamental problems of non-equilibrium quantum physics and strong quantum correlations, which have been identified in the UK as one of the main Physics Grand Challenges. Thus, if successful, this research will make its way to text-books, will broaden our general understanding of fundamental properties of matter, and will be part of this exciting knowledge, which will inspire the imagination of a new generation of students and encourage them to take physics degrees.

Class 3) PDRAs positions, funded by this project, and PhD studentships committed by the Department, will provide excellent career development and training opportunities by combining analytical and numerical research with direct interaction with experiment. The project will have a direct educational impact on UCL undergraduates (final year project students) by exposing them to challenging theoretical problems, relevant to state-of-the-art experiments. It will motivate them to continue onto research degrees and teach them skills relevant also in other type of employment (analysing data, comparing predictions of theoretical models to experimental results).

Class 4) Outcomes of this research will benefit other researchers (both experimentalists and theorists) working in the areas of circuit QED; polariton BEC, superfluidity and lattices; superconductivity, ultra-cold atomic gases, on control problems in quantum mechanics, on general non-equilibrium techniques, statistical physics, quantum optics, and condensed matter physics. They will benefit from the results, and from the methods and numerical codes developed.