Publication

Neutral atom arrays have emerged as a versatile platform towards scalable quantum computation and optimisation. In this paper we present first demonstrations of weighted graph optimization on a Rydberg atom array using annealing with local light-shifts. We verify the ability to prepare weighted graphs in 1D and 2D arrays, including embedding a five vertex non-unit disk graph using nine physical qubits. We find common annealing ramps leading to preparation of the target ground state robustly over a substantial range of different graph weightings. This work provides a route to exploring large-scale optimisation of non-planar weighted graphs relevant for solving relevant real-world problems. For more details see arXiv:2404.02658.

We have performed theoretical work on algorithmic benchmarking to evaluate the performance of near-term neutral atom processors accounting for realistic gate errors and atom loss. We show that for a 9 qubit system a quantum volume of 2⁹ is attainable, the maximum possible for this size of processor, highlighting the viability of using near-term neutral atom hardware for small-scale algorithms. For more details see arXiv:2402.02127.

We present an analysis of interspecies interactions between Rydberg d-states of rubidium and cesium. We identify the Förster resonance channels offering the strongest interspecies couplings, demonstrating the viability for performing high-fidelity two- and multi-qubit C_kZ gates up to k=4, including accounting for blockade errors evaluated via numerical diagonalization of the pair-potentials. Our results show d-state orbitals offer enhanced suppression of intraspecies couplings compared to s-states, making them well suited for use in large-scale neutral atom quantum processors. For more details see arXiv:2401.02308.

We have demonstrated high-fidelity randomised benchmarking of single qubit microwave gates across an array of 225 atoms, and non-destructive readout of up to 49 atoms. We achieved an average gate error of 8×10^-5 which is below the threshold for fault tolerant operations, highlighting the viability of neutral atoms for scalable computing. For more details see our paper Phys. Rev. Lett. 131, 030602 (2023) [arXiv].

We have demonstrated the UK’s first neutral atom two-qubit gate using a novel protocol based on electromagnetically induced transparency originally proposed back in 2008. We achieve a corrected CNOT gate fidelity of 0.82(6), mainly limited by available laser power. For more details see Phys. Rev. Lett. 129, 200501 (2022).

We have developed a robust protocol for implementing high-fidelity multiqubit controlled phase gates (C_kZ) on neutral atom qubits coupled to highly excited Rydberg states via adiabatic rapid passage (ARP). We find a CCZ gate with fidelity F > 0.995 for three qubits and CCCZ with F > 0.99 for four qubits is attainable in ∼ 1.8 μs via this protocol. For more details see our paper in QST.

This project is an EPSRC Prosperity Partnership with M Squared Lasers that aims to develop a new platform for quantum computing based on scalable arrays of neutral atoms that is able to overcome the challenges to scaling of competing technologies. We will develop new hardware to cool and trap arrays of over 100 qubits that will be used to perform both analogue and digital quantum simulation by exploiting the strong long-range interactions of highly excited Rydberg atoms. Together with the quantum software team lead by Prof. Andrew Daley, we will design new analogue and digital algorithms tailored for the neutral-atom platform to target industrially-relevant computation and optimisation problems.