Entangled quantum sensors: enhanced precision at the Heisenberg limit

Lead Research Organisation: University of Glasgow
Department Name: School of Engineering


Multi-body interactions enable the implementation of quantum-mechanically entangled multi-qubit states, and if used as a sensor will greatly improve its sensitivity. As today or near-term 'quantum' sensors still work without entanglement, an improvement in sensitivity can be the key break-through for achieving a quantum advantage, where true quantum sensors surpass the capabilities of classical technology. Here we will build the world's first multi-body sensor using superconducting circuits and use them to implement ensemble sensing and thereby greatly increase the circuit sensitivity -even more, if entangled. Our research plan starts from circuit concepts developed by me, implements these in cutting edge superconducting circuit technology and explores their applications in technology and blue-sky science. The vision of this project is the creation of a quantum sensor with multi-body interactions that allow for quantum speed-up in sensing with less hardware overhead than classical (not entangled sensors). A central aim is thus to generate UK based IP for a multi-body sensor which forms a highly important building block of future and near-term quantum sensors and imaging devices. Building on these sensors, the project will explore the generation of many-body states, and coupling them to an outer field. It will thus also open avenues to answer open physics and technology questions of high importance which remain challenging due to the difficulty of determining sources of decoherence in a many-body system. We are the first group to start building superconducting multi-body sensors and go in this research direction. This project will enable us to expand the lead we currently have. Compelling applications of our sensors are e.g. noise detection in quantum computers, or particle physics experiments.

Planned Impact

Here we summarise the impact of the project, grouped into the categories "science", "technology" and "people", where rather direct impact can be expected, and "society", where the impact will be of a more indirect nature.

The results of the project will advance the understanding of the quantum dynamics and decoherence of superconducting circuits. They will thus have an impact on all academic research related to this technological platform. The multi-qubit sensor we will implement will also trigger significant research effort in the optimization of quantum error correction. The results of our project will also enable a better understanding of local and global origins of noise and decoherence. They will thus have an impact on scientists working in these fields. Beyond the fields of condensed matter physics and quantum technology science, our result will also have an impact e.g. on research particle physics where our sensors are well-suited for dark matter detection.

We will introduce new functionalities for superconducting quantum sensors. These can be employed for the objectives we pursue but will also find use in other application of highest interest, such as quantum error correction, quantum computation or quantum material research. Our results will thus have a significant impact on current and future research and development in quantum technologies. This impact will be rather immediate for the UK based quantum technology programme, where it will be enhanced via our partnership with the UK Superconducting Quantum Technology Centre at Royal Holloway University, the UK Hub for Quantum Technology in Sensors and Metrology and also Oxford Instruments. Our project will, therefore, help to establish the UK as a leading centre for superconducting quantum technologies. Yet, the project's impact will reach further as it will make a significant contribution to the global effort of advancing superconducting quantum information processing to a technology readiness level with involvements of leading computing companies including IBM, Raytheon and Google.

The grant will also create immediate benefits for people who are involved in it or closely interact with the PI. The RA to be hired with the project funds will be supervised and trained by the PI and receive training in complementary aspects of the research field during visits to collaborators. Moreover, the PhD student associated with the project will receive training that ideally prepares her/him for an academic career. The PhD student will also receive training in many, highly transferable skills, e.g. into the area of circuit nanofabrication or quantum measurements, which will open rich perspectives for later employment inside or outside the academic sector. The PI will personally benefit from the grant as it will contribute to building up and strengthening his research groups.

The outreach activities within our project will generate impact in the society by raising awareness of the functioning and opportunities of quantum technology, in particular of entanglement, and sensing applications.
Description An article has been published, https://arxiv.org/abs/2211.08344. This article describes the optimization of the quantum-enhanced sensing of external magnetic fluxes with a Kitaev phase estimation algorithm based on a sensor with tunable transmon qubits. It provides the optimal flux biasing point for sensors with different maximal qubit transition frequencies. An estimation of decoherence rates is made for a given design. T
Exploitation Route Quantum sensors are up and coming, this work will contribute to their technological readiness level.
Sectors Digital/Communication/Information Technologies (including Software)

Description National Physical Laboratory 
Organisation National Physical Laboratory
Country United Kingdom 
Sector Academic/University 
PI Contribution Sample and knowledge exchange with the superconducting quantum computing group at NPL
Collaborator Contribution Sample and knowledge exchange with the superconducting quantum computing group at NPL
Impact Joint funding bids (Innovate, EPSRC), joint student supervision
Start Year 2019
Title quantum circuit measurement software on github 
Description Qkit - a quantum measurement suite in python The qkit framework has been tested under windows and with limits under macos x and linux. The gui requires h5py, qt and pyqtgraph, which work fine on these platforms. The core of the framework should run with python 2.7.x/3.4+ https://github.com/QuantumCircuits-Glasgow 
Type Of Technology Webtool/Application 
Year Produced 2021 
Open Source License? Yes  
Impact Open source measurement software for superconducting quantum circuits including spectroscopic and time-domain data taking and analysis. 
URL https://github.com/QuantumCircuits-Glasgow