Spatial Division Multiplexing for Cold-Atom-Based Quantum Memory

Project Information

Multiplex

Grant agreement ID: 101029591

DOI

10.3030/101029591

Project closed

EC signature date 18 February 2021

Start date 1 March 2021

End date 28 February 2023

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 196 707,84

EU contribution

€ 196 707,84

Coordinated by

SORBONNE UNIVERSITE
France

Periodic Reporting for period 1 - Multiplex (Spatial Division Multiplexing for Cold-Atom-Based Quantum Memory)

Reporting period: 2021-03-01 to 2023-02-28

Summary of the context and overall objectives of the project

The project originally aimed at adapting and exploiting space division multiplexing (SDM), a technology which recently received a lot of attention in telecommunication technologies as a method for increasing communication channels data capacity, to demonstrate the parallel storage of a large number of photonic qubits in a quantum memory based on a cold atomic ensemble with near-unity efficiency. The project's approach stood out in that, by using SDM, the parallelization of the storage protocol could be done while preserving the memory efficiency for each spatial mode. This, in turn, circumvents the typical tradeoff between increased rate and
memory efficiency, as often encountered when resorting to other multiplexing methods.

The project unfortunately failed to achieve critical objectives or milestones and, as such, has been severely delayed. However, the work carried out within this fellowship serves the scientific community as a whole and has an important impact on the technological development of quantum memories from an industrial standpoint. The demonstration of a multiplexed protocol compatible with atom-based quantum memories is valuable for industries hoping to transfer quantum information over long distances.

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

Simulations were carried out to lay the groundwork of interfacing the SDMs with our cold-atom-based memory and to make sure its capacity was well above the 20 modes provided by the SDM devices. The simulation results show that the maximum efficiency only drops significantly after about 100 modes are stored simultaneously. This result, marks a significant step forward towards the main goal of the project.

Progressive updates on the project, along with results obtained in the framework of the experiment running on the main setup were presented at the following conferences:

- GDR IQFA 2021 – Lyon (poster)
- Guest lecture at the Okinawa Institute of Science and Technology to students of the “Introduction to Atomic Physics” class 2022 - Okinawa
- QCMC 2022 - Lisbon (poster prize and talk)
- GDR IQFA 2022 – Saclay (poster)

Along with these events, the fellow also participated in the open days of the host institution (2 years consecutively), and took part in events during the “Fête de la Science” called Speed Meetings (2 years consecutively), in which high school students would get to meet and interact directly with scientists.
A scientific article reporting on our latest results on the main experiment is currently in preparation. These results have not yet been published but were presented at all the events listed above and were even attributed the best poster prize at the QCMC 2022 conference, which then led to a talk.

Experiments are currently being carried out in the single-photon regime using attenuated coherent beams and important work on phase stabilization between two-optical paths corresponding to polarization modes was performed. As these experiments use the same optical paths that will be used by the SDM devices once they are incorporated to the main experimental setup, achieving phase stabilization, even at a reduced number of modes, is a significant advance towards completion of the main objective.

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)

Our simulations have shown that this type of quantum memory is highly suitable for applications in quantum networks. Moreover, the new experimental capabilities added to the setup have made it robust to various sources of noises and instabilities, leading to results in quantum cryptography never reached before. Now that the various technical difficulties have been addressed and solved, the original plan of the multiplexing project should be resumed as per previously proposed.

Completed in continuous reporting