FINAL REPORT ON THE Max Planck Workshop of

“QUANTUM SENSING WITH QUANTUM CORRELATED SYSTEMS”.

Dresden, 25-29 September 2017

Organizers: S. Rachel (Univ. Merlbourne ), M. Oberthaler (Univ. Heidelberg) and A. Sanpera (Univ. Aut. Barcelona)

**1. ****Focus of the workshop**

The focus of the workshop “Quantum sensing with quantum correlated states” has been to joint together worldwise experts in the many facets involving quantum metrology. Quantum metrology with strongly correlated systems is a truly multidisciplinary area and we aimed at putting together scientist working in quantum information processing, condensed matter, ultracold gases, quantum dots etc.. in order to explore how quantum correlations, on their broader sense, can be used for improved sensing beyond classical limits.

Quantum information theory has helped developing a precise language with an ample vocabulary for the characterization of quantum systems based on quantum correlations. Undoubtedly, the theory of entanglement has provided a new set of powerful tools to gain understanding about many-body strongly correlated systems by explicitly considering the tensorial product structure of the composite states. Quantum correlations put in evidence the importance of such tensorial structure. Therefore, the workshop has also been very useful to question fundamental topics about characterization and quantification of highly entangled quantum states in interacting many particle systems. The combination of fundamental theoretical aspects with experimental activities in the context of metrology and synthetic quantum matter provides a unique opportunity to explore new possibilities. Sensing is one of the tasks in which quantum correlated states can over perform the efficiency of classical systems to determine a parameter and has applications in many other areas of science. Special emphasis on magnetometry and magnetic gradients using strongly correlated systems has been discussed.

**2. ****Participants**

The list of invited speakers included both, very relevant and stablished figures in different disciplines, both experimental and theoretical, with young scientist with already promising contributions on the field. In experiments, particularly remarkable were the contributions of J. Bollinger (NIST, USA), Steve Girvin (Yale, USA), D. Budker (Germany), E. Polzik (Univ. Copenhagen), Monika Schleier-Smith (MIT, USA) and several others. In the theory, the work of A. Smerzi (Florence, Italy), Ana Maria Rey (NIST, USA), Israel Klich (USA), M. Heyl (Germany) where also very remarkable. In general, we have prioritized the scientific contact and discussions between the participants allowing to this aim a lot of time for discussions. To achieve this goal we enhanced scientific exchange and reduced the number of talks. Invited speakers were asked to spend 10’ of their time slot to introduce their subject to the audience and to present their results in the frame of quantum sensing. A large majority of the speakers did so, as a consequence, in a large part of the invited talks, questions from the participants extended far away from the allocated discussion of time. That has helped to the newcomers to feel in a very open and relaxed atmosphere and to discuss together very vividly.

Unfortunately, due to the fact that the workshop time-slot was allocated on the third week of September of 2017, and on the first week of September, the biannual conference on Bose-Einstein Condensation took place in Spain, few remarkable scientists outside Europe which were initially accepted had to decline due to the impossibility of doing two trips to Europe within two weeks. be an invited speaker, decline because travelling twice to Europe was not possible form them.

**3. ****Expected Outcomes**

Several outcomes are to be expected as a consequence of the workshop, mostly motivated from

(i) A timely research topic

(ii) First interdisciplinary workshop on quantum metrology

(iii) The talks presented by the invited speakers

(iv) The interdisciplinary participation with people from distinct scientific areas

The possibility of opening common projects have been discussed at length by the European participants. In general, we believe that the potential outputs of the workshop are very high.

A lot of different ideas about quantum sensors with many different applications are now starting to be developed and new collaborations between different groups is a reality due to the workshop. To give some examples, Prof. A. Smerzi (Italy) has been invited by Prof. A. Sanpera (Spain) in January 2019 to initiate a joint work on metrology. The student A. Yuste (Barcelona) has been invited by the Dr. P. Hauke (Heidelberg) for a research stage based on quantum sensing. A lot of discussion were also devoted to prepare joint common projects for the next European calls.

Finally, we would like to mention that the organization and facilities offered by the M. Planck Institute at Dresden were very helpful. We truly appreciated this invaluable help regarding financial support, infrastructure, and last but not least the efficiency before, during and after the workshop of Mrs. C. Domaschke.

Prof. Dr. Anna Sanpera on the behalf of the organizers