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.
Our hardware is based on holographic trapping of arrays of identical atomic qubits. Traps are initially loaded at random, after which they are sorted to generate deterministically loaded qubit arrays. To connect our qubits we take advantage of the strong long-range interactions between Rydberg atoms to couple each qubit to its surrounding neighbouring qubits to perform deterministic two and multi-qubit gate operations. Following implementation of the quantum algorithm, qubits are readout using state-selective fluorescence measurements.
A unique advantage of the neutral atom platform is that, unlike competing technologies, the fidelity of the Rydberg mediated gates doesn’t drop as the system size is increased providing an attractive route to scalable quantum computing.
This Prosperity Partnership enables us to work directly with M Squared Lasers, the global leaders in supplying commercial laser systems to quantum computing activities around the world, whose low noise, high power Equinox and SolsTiS laser systems provide the key enabling technology to achieving both scalability and high fidelity qubit operations for our neutral atom platform. Outputs from SQuAre team at Strathclyde have been exploited by M Squared to develop Maxwell, the UK’s first commercial neutral atom computing platform which was officially launched at the 2022 UK Quantum Technology Showcase – for more details see here.
Highlights
Randomised benchmarking and non-destructive readout |
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We have demonstrated high-fidelity randomised benchmarking of single qubit microwave gates across an array of 225 atoms using conventional readout techniques using strings of up to 1000 random gates. 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.
We further demonstrated non-destructive readout using state-selective imaging on the stretched state transition to enable post-selection for loss and avoiding the requirement to reload the arrays after every sequence. For more details see our paper on the arXiv:2301.10510 (2023). |
High-fidelity multi-qubit gate operations |
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We have developed a robust protocol for implementing high-fidelity multiqubit controlled phase gates (CkZ) on neutral atom qubits coupled to highly excited Rydberg states. Our approach is based on extending adiabatic rapid passage (ARP) to two-photon excitation via a short-lived intermediate excited state common to alkali-atom Rydberg experiments, accounting for the full impact of spontaneous decay and differential AC Stark shifts from the complete manifold of hyperfine excited states. We evaluate and optimisze gate performance, concluding that for Cs and currently available laser frequencies and powers, 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. Higher fidelities are accessible with future technologies, and our results highlight the utility of neutral atom arrays for the native implementation of multiqubit unitaries. For more details see the paper in QST. |
Experiment Gallery |
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Close up of experiment chamber |
Publications
- B. Nikolov, E. Diamond-Hitchcock, J. Bass, N.L.R Spong and J.D. Pritchard, Randomized Benchmarking using Non-Destructive Readout in a 2D Atom Array, arXiv:2301.10510 (2023)
- G. Pelegri, A. Daley and J.D. Pritchard, High-fidelity multiqubit Rydberg gates via two-photon adiabatic rapid passage, Quantum Sci. Technol. 7, 045020 (2022)
Team Members: Jonathan Bass, André Oliveira, Boyko Nikolov, Elliot Diamond-Hitchcock
Former Members: Nicholas Spong
Funding:
