Optimal Control of Trapped Ions

Quantum Computing and Simulation Hub

Trapped ions are among the most promising platforms for quantum information processing. All basic logical operations have been realised with high accuracy, but there are a few hurdles to overcome in order to make trapped ions a scalable technology.

The goal of this PhD project is to employ tools from optimal control theory in order to guide the dynamics of trapped ions. This shall enable shuttling ions through a potential landscape, so that any ion can be made to interact with any other ion.

This work is mostly theoretical and computational, done in collaboration with the Ion Quantum Technology Group at the University of Essex, and interest in collaborating with an experimental partner is essential.

For inquries about the project, please contact Florian Mintert.

Quantum simulators based on multiphoton interference

Funder: ERC, Marie Curie International Training Network

Quantum photonics is a promising platform for near-term quantum simulation and intermediate-scale computation. Boson sampling—where the propagation of photons in large static interferometers is inherently hard to simulate classically has been identified as a leading experimentally accessible architecture which may exhibit a quantum advantage for certain tasks. One known case is a mapping from vibrational excitations in molecules to photons, which can be exploited to calculate certain useful quantities in chemistry [3]. Beyond this, there exists a broad landscape of physical systems which could possibly be emulated using a boson-sampling style architecture: systems of electrons and interacting particles or spins appear more challenging to map onto photons, but could ultimately lead to many more applications to real-world problems by modelling quantum materials, chemistry, and condensed matter physics.

This project will use multiphoton interference in guided-wave circuits to simulate other physical systems. New simulation schemes will be developed to map photonic states onto a wider variety of physical systems, exploring molecular vibrational spectra; spin chains and fermionic systems; and electrons interacting with a lattice containing vibrational modes, a precursor for superconductivity. This will involve collaboration with theorists from the groups of Magdalena Stobinska (Warsaw) and Myungshik Kim (Imperial). Experimentally, the ESR will collaborate with Paderborn to optimise waveguide SPDC, and with NIST on photon-number-resolving-detectors. At Quandela, the ESR will work with deterministic single-photon sources and fibre-based interferometers acting on the time-bin degree of freedom. Simulators will be demonstrated in tailored interferometric circuits, which depending on the nature of the circuit will make use of integrated photonics (i.e. silicon, silicon nitride, or silica waveguides) or optical fibre architectures.

Within UFQO, the student would have access to newly refurbished quantum optics laboratories and equipment including photon-number-resolving superconducting TES (the only system of its type in the UK), an array of 32 superconducting nanowire single photon detectors, single-photon sources based on parametric down-conversion and four-wave mixing, various pulsed and continuous-wave laser systems, and photonic-chip alignment and characterisation setups. Training on equipment and day-to-day supervision would be provided by an expert team of researchers within UFQO. Additional resources are also available in the form of departmental lecture courses and the Quantum Systems Engineering Skills and Training Hub.

Should you require further information please contact Dr Raj Patel.

Quantum simulators based on integrated photonics

Funder: EPSRC, UK National Quantum Technologies Program hub for Quantum Computing & Simulation

Quantum photonics is a promising platform for near-term quantum simulation and intermediate-scale computation. Boson sampling—where the propagation of photons in large static interferometers is inherently hard to simulate classically has been identified as a leading experimentally accessible architecture which may exhibit a quantum advantage for certain tasks. One known case is a mapping from vibrational excitations in molecules to photons, which can be exploited to calculate certain useful quantities in chemistry [3]. Beyond this, there exists a broad landscape of physical systems which could possibly be emulated using a boson-sampling style architecture: systems of electrons and interacting particles or spins appear more challenging to map onto photons, but could ultimately lead to many more applications to real-world problems by modelling quantum materials, chemistry, and condensed matter physics.

This studentship will investigate how near-term photonic architectures could be used to perform two classes of simulations. The first will utilise Gaussian boson Sampling and weak-field homodyne detection to calculate Franck Condon factors in the estimation of vibronic energy spectra. The student will leverage our state-of-the-art down-conversion single-photon sources and superconducting transition edge sensors (TES) to perform operations to simulate vibronic spectra. The student will extend this to systems at non-zero temperature, and study strategies to treating anharmonic potentials via measurement-based nonlinearities. The second will investigate how engineered distinguishability using multiple degrees of freedom of photons can provide access to mixed-particle couplings to enable simulation of a broad range of materials and condensed matter systems. Low-dimensional subspaces of high-dimensionally encoded photons exhibit mixed statistics, and by varying these degrees of freedom one could isolate fermionic behaviour or a coupled bosonic-fermionic system such as those described by the Holstein model relating to electron-vibrational coupling in molecules and superconductors. Additional pathways include operator mappings between different quantum systems, such as the Jordan-Wigner transformation between fermions and spins, Jordan-Schwinger maps from spins to bosonic modes, and bosonisation identities for many-body fermionic systems, all needed for simulation of important classes of materials.

Within UFQO, the student would have access to newly refurbished quantum optics laboratories and equipment including photon-number-resolving superconducting TES (the only system of its type in the UK), an array of 32 superconducting nanowire single photon detectors, single-photon sources based on parametric down-conversion and four-wave mixing, various pulsed and continuous-wave laser systems, and photonic-chip alignment and characterisation setups. Training on equipment and day-to-day supervision would be provided by an expert team of researchers within UFQO. Additional resources are also available in the form of departmental lecture courses and the Quantum Systems Engineering Skills and Training Hub.

Should you require further information please contact Dr Raj Patel.