Phononic Quantum Sensors for Gravity

Project Information

PhoQuS-G

Grant agreement ID: 832250

DOI

10.3030/832250

Project closed

EC signature date 18 March 2019

Start date 1 October 2019

End date 1 December 2021

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 162 806,40

EU contribution

€ 162 806,40

Coordinated by

HUMBOLDT-UNIVERSITAET ZU BERLIN
Germany

Periodic Reporting for period 1 - PhoQuS-G (Phononic Quantum Sensors for Gravity)

Reporting period: 2019-10-01 to 2021-09-30

Summary of the context and overall objectives of the project

Bose-Einstein condensates (BECs) are extremely cold Bose gases consisting of a large number of interacting atoms. BECs have quantum properties that can be exploited perfectly for high precision metrology. The goal of the research project Phononic Quantum Sensors for Gravity (PhoQuS-G) is an extensive analysis of the use of phonons (quasi-particles of phase and density perturbations) in BECs for high precision sensing of gravitational fields. A clear pathway will be given towards first gravimetry experiments with phonons in BECs. Such experiments can lead to the development of phononic quantum sensors, a very promising quantum technology. High precision sensing of gravitational fields offers a variety of applications - from fundamental research to technological solutions; for example, knowledge about local gravitational fields (geodesy) can be used to map underground infrastructures, find natural resources or ease navigation. As BECs exist on the micrometer scale, precise measurements of gravitational fields on short distances and of very small objects can be implemented far beyond the scales explored to date. This may offer opportunities for new exciting experiments investigating the interface of quantum mechanics and gravity.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

In the first part of the project, general properties of phonons in BECs for quantum sensing have been analysed. A focus has been particularly on the influence of an internal decay process, three-body loss, which leads to the loss of three atoms from the condensate. A result of the work for this project has been that three-body loss leads to strong restrictions of the utility of phonons in BECs for quantum sensing. The analysis and the results have been published in an article (available as open access on the preprint server Arxiv) and presented at workshops and conferences.
In another part of the project, an optomechanical setup of light coupled to phonons in BECs has been theoretically developed. Furthermore, the utility of the setup has been investigated. It has been found that it will be very hard to achieve quantum sensing with the setup in general and the classical sensing abilities for example applications like gravity-gradiometry are very limited due to practical limitations. The results have been published in a pre-print article that will be sent to a journal soon.
It has also been investigated if optomechanical systems (of which the one based on phonons in BECs is only one explicit example) can be used for sensing of the gravitational field of light. In this context, an explicit proposal was developed based on a different implementation of optomechanics with a levitated solid-state object. The results have been published as pre-print and are under revision by New Journal of Physics.
Another category of gravitational effects are local effects of the cosmological expansion. If those may be observable when quantum sensing is employed has been investigated as part of this project. It has been shown that the effects are far from measurable and a publication has been uploaded to a preprint repository and submitted for peer reviewing to the journal Classical and Quantum Gravity.
The Quantum Klystron, a novel technique to manipulate cold atoms (the constituents of a BEC) has been theoretically developed in another sub-project. The proposal can be implemented with state-of-the-art technology. These results have been published in Physical Review Research. As part of this project, the ER has contributed an experimental investigation of dipole-dipole interactions within a BEC and to an upcoming publication about the topic.
For further dissemination of the results of the project, the two outreach projects “Gravitational fields of motion” and “Sciddle - PhoQuS-G Edition” have been commissioned and supervised.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The effect of three-body loss in BECs on the utility of phononic quantum sensors was an important step beyond the state-of-the-art. Only after this analysis, the clear limitations and guidance for future investigations have been possible. In particular, the result has shown the need to consider alternative systems like Fermionic quantum gases or solid-state systems.
Quantum Klystron is a novel technique to manipulate the state of atoms that can be used for quantum technologies. It can be expected that the technique will be further developed and experimentally implemented in the next years. It may become an important technology in quantum optics and lead to further progress in other applications.

BEC in front of moving mass