Scalable Qubit Arrays for Quantum Computing and Optimisation (SQuAre)

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 Showcasefor more details see here.

Experiment Gallery


Randomised benchmarking and non-destructive readout
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, 03602 (2023) [arXiv].
Two-Qubit EIT Gate Protocol
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).
High-fidelity multi-qubit gate operations
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 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.


Randomized Benchmarking Using Nondestructive Readout in a Two-Dimensional Atom Array. Physical Review Letters 131, 030602 (2023).


High-fidelity multiqubit Rydberg gates via two-photon adiabatic rapid passage. Quantum Science and Technology 7, 045020 (2022).



We acknowledge funding from the following sources: