Rydberg Atom Quantum Technologies

Welcome to the Rydberg Atom Quantum Technologies team lead by Prof. Jonathan Pritchard, an RAEng Senior Research Fellow at the University of Strathclyde.

Overview

Rydberg atoms are atoms excited to extremely large principal quantum numbers resulting in giant atoms offering exaggerated properties including enormous electric-dipole moments in the microwave frequency range and strong, tuneable long-range interactions. Our research is focused on developing new quantum technologies that exploit these properties to develop scalable platforms for quantum computation and optimisation, and atomic gas sensors for precision microwave field detection and imaging.

Please contact jonathan.pritchard@strath.ac.uk if you are interested in working in within one of our research areas – we have both PhD and PDRA positions available (see below for details) across focused on developing neutral atom quantum computers based on scalable arrays of neutral atoms.

Research

Quantum Error Correction (QuERy)
This project, supported by a Royal Academy of Engineering Senior Research Fellowship and M Squared Lasers, seeks to develop a new experiment focused on creating dual-species arrays of Cs and Rb for quantum error correction. This is integrated within a 4K closed-cycle cryostat to obtain extended trap lifetime for scaling to large numbers of qubits, and will focus on exploiting long-range dipole interactions between Rydberg states of each species to enable mid-circuit, non-destructive readout and generation of topologically protected logical qubits as a route towards fault tolerant digital quantum computing.

Quantum Error Correction (QuERy)
Scalable Qubit Arrays (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.

Scalable Qubit Arrays (SQuAre)
ARC:Alkali Rydberg Calculator
An open-source python library for calculating properties of Alkali Rydberg atoms developed with Nikola Sibalic, Charles Adams and Kevin Weatherill at JQC in Durham. Full details on the arXiv:1612.05529 - download source from GitHub.


ARC:Alkali Rydberg Calculator
Quantum Lidar
In collaboration with the theory team lead by Prof. John Jeffers and supported by DSTL, we are developing new approaches to quantum enhanced LIDAR by creating a compact optical frequency comb source for pumping birefringent optical fibres and exploring a new log-likelihood metric to perform quantum enhanced stand-off detection and range-finding.

Quantum Lidar

Latest News

Demonstration of weighted graph optimization on a Rydberg atom array using local light-shifts
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.
Demonstration of weighted graph optimization on a Rydberg atom array using local light-shifts
Benchmarking the algorithmic performance of near-term neutral atom processors
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.
Benchmarking the algorithmic performance of near-term neutral atom processors
Demonstration of quantum-enhanced rangefinding robust against classical jamming
Our results demonstrating a correlated pair-source to perform target detection and range-finding to show the resilience of quantum-enhanced lidar to classical jamming have been published in Optics Express.
Demonstration of quantum-enhanced rangefinding robust against classical jamming
Interspecies Förster resonances of Rb-Cs Rydberg d-states for enhanced multi-qubit gate fidelities
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 CkZ 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.
Interspecies Förster resonances of Rb-Cs Rydberg d-states for enhanced multi-qubit gate fidelities
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, 030602 (2023) [arXiv].
Randomised benchmarking and non-destructive readout
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).
Two-Qubit EIT Gate Protocol
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.
High-fidelity multi-qubit gate operations

Team

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Paul Schroff

PhD student

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Dr André de Oliveira

Postdoc

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Dr Daniel Walker

Postdoc

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Dr Kieran Craig

Postdoc

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Elliot Diamond-Hitchcock

PhD student

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Ian Moodie

PhD student

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Maximillian Wells-Pestell

PhD student

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Paul Ireland

PhD student

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Prof Jonathan Pritchard

Professor

Publications

P. M. Ireland, D. M. Walker, J. D. Pritchard, Interspecies Förster resonances for Rb-Cs Rydberg d-states for enhanced multi-qubit gate fidelities. Physical Review Research 6, 013293 (2024).

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K. McInroy, N. Pearson, J. D. Pritchard, Benchmarking the algorithmic performance of near-term neutral atom processors. (2024).

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M. P. Mrozowski, R. J. Murchie, J. Jeffers, J. D. Pritchard, Demonstration of quantum-enhanced rangefinding robust against classical jamming. Optics Express 32, 2916 (2024).

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A. G. de Oliveira, E. Diamond-Hitchcock, D. M. Walker, M. T. Wells-Pestell, G. Pelegrí, C. J. Picken, G. P. A. Malcolm, A. J. Daley, J. Bass, J. D. Pritchard, Demonstration of weighted graph optimization on a Rydberg atom array using local light-shifts. (2024).

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B. Nikolov, E. Diamond-Hitchcock, J. Bass, N. L. R. Spong, J. D. Pritchard, Randomized Benchmarking Using Nondestructive Readout in a Two-Dimensional Atom Array. Physical Review Letters 131, 030602 (2023).

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M. P. Mrozowski, J. Jeffers, J. D. Pritchard, High-efficiency coupled-cavity optical frequency comb generation. Optics Continuum 2, 894 (2023).

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M. P. Mrozowski, R. J. Murchie, J. Jeffers, J. D. Pritchard, Demonstration of quantum-enhanced rangefinding robust against classical jamming. (2023).

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R. J. Murchie, J. D. Pritchard, J. Jeffers, Object detection and rangefinding with quantum states using simple detection. (2023).

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K. McDonnell, L. F. Keary, J. D. Pritchard, Demonstration of a Quantum Gate Using Electromagnetically Induced Transparency. Physical Review Letters 129, 200501 (2022).

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G. Pelegrí, A. J. Daley, J. D. Pritchard, High-fidelity multiqubit Rydberg gates via two-photon adiabatic rapid passage. Quantum Science and Technology 7, 045020 (2022).

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Funding

We acknowledge funding from the following sources:

Open Positons

We are always keen to recruit highly motivated post-doctoral researchers and student’s. Current vacancies are listed below, however if you don’t see a vacancy for the research project you are interested in please contact jonathan.pritchard@strath.ac.uk for more details.

Quantum Error Correction in a dual species Rydberg Array (QuERy)
The QuERy project is focused on development of a dual-species platform for neutral atom quantum computing to address the major barriers to scaling existing platforms from 100s to thousands of qubits, namely extending atom array trapping lifetimes through integration in a cryogenic environment and enabling active error correction through the ability to perform cross-talk free, state-selective local measurements.
Oct 26, 2023
Quantum Error Correction in a dual species Rydberg Array (QuERy)
Scalable Qubit Arrays for Quantum Computation and Optimisation
This project will utilise the advanced SQuAre neutral atom quantum computing platform developed at Strathclyde, offering up to 225 qubits. The aim is to perform pioneering demonstrations of small-scale digital and analogue algorithms relevant for addressing industrially relevant real-world problems relating to optimisation as well as studies of many-body quantum systems.
Oct 26, 2023
Scalable Qubit Arrays for Quantum Computation and Optimisation
High Fidelity Entanglement in a trapped ion chain
We are seeking to recruit a PhD student to work embedded within the trapped ion team at NPL lead by Dr. Alastair Sinclair to demonstrate multi-qubit entanglement in a 1D ion chain suitable for next-generation quantum metrology.
May 1, 2023
High Fidelity Entanglement in a trapped ion chain

Previous Projects

Microwave Field Sensing using Rydberg atoms
RF fields in the microwave and terahertz domain are ubiquitous for security and communications, however test equipment requires frequent recalibration and careful understanding of the perturbations caused by the antenna used for measurement. This project, a collaboration between researchers at the University of Strathclyde and Durham University, seeks to develop new all-optical field sensors operating in the microwave and terahertz domain using Rydberg atoms in a thermal vapour to act as microscopic antenna enabling metal-free probing, sub-wavelength imaging resolution and the ability to implement a traceable SI calibration offering superior sensitivity compared to existing technologies. Early results include a careful characterisation of linearity and optimal state choice for precision RF sensing using this approach.

Microwave Field Sensing using Rydberg atoms
Hybrid Quantum Interface

As part of an EPSRC Quantum Technology Fellowship we developed a new experimental apparatus to perform two-qubit operations using individually trapped Cs atoms. Highlights from this work included first demonstrations of single atom imaging using an sCMOS camera, high-fidelity and long-coherence entanglement generation and the first native CNOT gate protocol based on electromagnetically induced transparency. This apparatus has now been rebuilt as part of the Quantum Error Correction using Cryogenic Dual-Species Arrays project which builds on these early milestones and will integrate the system into a 4 K cryostat.

Separately we investigated hybrid approaches to quantum networking by developing optimised NbN resonators at 15 GHz for coupling Rydberg states to superconducting microwave circuits in a 4 K environment in collaboration with the Quantum Devices group at Glasgow University lead by Martin Weides. We have shown theoretically that this system can be used for demonstrations of strong-coupling and active cooling providing Q factors of 105 and above can be achieved.


Hybrid Quantum Interface