The project objective is the development of interfaces for the coherent conversion of radio and microwave frequencies to the optical domain, utilizing various approaches, which can be scaled down to the quantum level of few quanta. 
Our ultimate goal, as it often occurs in many other human activities, is to
"turn up the signal, wipe out the noise ....send out the signals deep and loud"
["Signal To Noise" ,  "Up", Peter Gabriel 2002]
The project has the following more specific objectives:
1) realization of a coherent microwave-to-optical link, based on a cavity-electro-optical setup;
2) implementation of coherent interconversion between microwave/optical photons and MHz/GHz phonons;
3) implementation of a nanomechanical interface for microwave-optical interconversion.
Expected impact
By the end of the project, we expect to build and test significant examples of nanomechanically-based microwave-optical interfaces operating close to the quantum level. The project results may have a profound impact on the methods currently used for information processing. In fact, in the last decade, the transformation of light into electrical signals and/or microwave signals has significantly improved; nonetheless these techniques cannot be straightforwardly scaled down to the quantum domain. In fact, quantum communication requires a coherent storage interface. We expect to reach the regime where the coherent transfer between photons and phonons can be realized opening interesting perspectives for the development of quantum opto-electro-phononics.
A further important consequence of the success of our project is related to the possibility to detect microwave and radiofrequency signals with the same high efficiency and comparable speed currently attainable only with optical signals. Moreover, nanomechanical resonators could be operated in the nonlinear Duffing regime and used as mixers or in circuits for amplifying purposes; one could get revolutionary achievements if they could be operated up to the largely unexplored THz regime for the realization of terahertz spectrum analyzers operating at room temperature, highly sensitive detectors for molecules, stand-off security imaging, and medical diagnostics.
A prerequisite for the realization of efficient nanomechanical interfaces is the ability to build and operate nanomechanical resonators with mechanical quality factors above one million and at the same time very good optical or electrical properties. These devices could be useful in other technological areas: for example, the possibility to integrate mechanical elements with considerably long relaxation times within optoelectronic solid-state devices will provide unique opportunities for the realization and integration of classical and quantum memories with extremely long lifetimes.

Executive summary
The FET-Open project iQUOEMS (Interfacing Quantum Optical Electrical and Mechanical Systems) is one of the FP7 projects funded by the European Commission within the emerging field of hybrid nano-opto-electro-mechanical systems. Its main goal was to explore the potentialities of hybrid micro- and nano-mechanical devices for mixing, converting and redistributing optical and electromagnetical signals, especially in the regime where the quantum properties of light and microwaves can be exploited for a more efficient distribution of information.
iQUOEMS has successfully achieved such a goal, and with its scientific results has firmly established nano-opto-electro-mechanical systems as an important platform for the realization of the second quantum revolution which will be realized within the incoming Quantum Technology Flagship.
With its scientific and dissemination activities, the iQUOEMS project has represented an important bridge between the FP7 FET-Open project MINOS, (Micro- and Nano-Optomechanics for ICT and QIPC’), the first project funded in the world in the arising field of cavity optomechanics, and the relevant subsequent H2020 FET-Proactive 2016-17 Programme, aimed at boosting emerging technologies. The fact that two of the twelve funded projects in this call, HOT (Hybrid Optomechanical Technologies), and VIRUSCAN (Optomechanics for Virology), are now carrying out RD activities strongly related to those afforded within iQUOEMS, witnesses the pivotal and influential role of our FET-Open project. In particular the fast and efficient transduction of optical and microwave signal via nanomechanical degrees of freedom is one of the pillar of the HOT project.
Some additional iQUOEMS facts:
• The 59 project publications include 17 publications in high-impact journals including Nature, Nature Communications, Physical Review Letters, Physical Review X, Applied Physics Letters, Proceedings of the National Academy of Sciences.
• iQUOEMS researchers have delivered 153 invited lectures and seminars at international conferences, workshops and colloquia.
• iQUOEMS researchers have been awarded 9 prestigious national and international Prizes and Awards within the duration of the project.
iQUOEMS has also established a strong interaction with the FP7-ITN-PEOPLE project “cQOM”, “Cavity Optomechanics”, which provided high-level training in this emerging technological field. In fact, two joint cQOM-iQUOEMS meetings have been held at Diavolezza (CH) in February 2015 and 2016, where both young researchers and group leaders, also operating within industries, discussed about optomechanics in an informal atmosphere. The final iQUOEMS conference, “Quantum Interfaces with Nano-opto-electro-mechanical-mechanical Devices: Applications and Fundamental Physics” has been held in Erice (Sicily, Italy) on August 1-5 2016, with both European and non-European speakers. 
In summary, iQUOEMS has achieved most of its scientific and technological goals: in particular it has provided proof-of-principle demonstrations of the mechanical transduction between signals at vastly different wavelength, of photon-phonon conversion in the quantum regime, and of quantum-limited microwave amplifiers of novel designs. These results strengthen the role of opto-electro-mechanical devices as a fundamental ingredient for the development of quantum technologies, especially as universal transducers in quantum communication network and as quantum sensors.
Potential impact
The project iQUOEMS has been based on a high-risk research programme, aiming at exploring how the impressive recent progress in nanofabrication techniques could be exploited for the realization of novel devices able to collect, store and redistribute data and information. The project focused in particular on the interconversion of signals with vastly different wavelengths and on the key role that can be played by high-quality nanomechanical resonators. iQUOEMS have achieved not all but most of its ambitious goals, demonstrating nonetheless significant progress with respect to the state-of-the-art in all its scientific targets.
We now review the main results achieved within the project duration and their potential impact, at the scientific, technological and societal level.

  1. First demonstration of photon-phonon correlations at the quantum level with an integrated nanomechanical device (R. Riedinger e al., Nature (London), 530, 313-316 (2016)). The correlated generation, conversion and readout of single-photon-phonon pairs is a technological primitive that can be used in many signal transfer protocols. iQUOEMS scientists have shown that this correlated manipulation and readout can be carried out at the quantum level, with an optomechanical device that could be easily integrated on chip, and this may lead to many useful applications for the development of quantum technologies. In fact, photon-phonon conversion at the quantum level can be used for storing, retrieving quantum information and for the realization of integrated, long-lived quantum memories, also profiting for the extremely long coherence time of high-Q nanomechanical resonators.
  2. Demonstration of low-noise, near-quantum-limited microwave amplifiers, based on novel concepts and regimes. Also such a significant advance demonstrated by the iQUOEMS results is of fundamental importance for the advent of the second quantum revolution and for the development of quantum technologies. In fact, microwave control and readout at the quantum level are mandatory for any quantum information processor based on superconducting technologies, which is currently the preferred platform for the realization of quantum computers, already chosen by Google, IBM, and already applied (even if still debated) by the D-Wave company. The microwave amplifiers demonstrated within iQUOEMS could be again easily integrated within existing platforms, and exploit the use of graphene and carbon nanotubes, or properly engineered mechanical resonators.
  3. Design of quantum communication protocols for the exchange of quantum information between distant superconducting qubits and for quantum target detection with microwaves (“quantum radar”). These are theoretical results which unambiguously show a quantum advantage and which could be also profitably used in the explicit realization of quantum network and for quantum sensing in noisy environments.

In more general terms, iQUOEMS has provided a number of relevant demonstrations of opto-electro-mechanical systems operating in the quantum regime, providing further evidence of the key role that these hybrid platforms will play within the incoming Quantum Technology Flagship. Therefore we can say that the impact of iQUOEMS is already relevant within the scientific and technological context, because it has represented the perfect link between a number of FP7 FET projects focusing on hybrid nano-opto-electro-mechanical technologies, and the incoming relevant European investment of the Quantum Technology Flagship.
However, iQUOEMS has reached further excellent results which may have a relevant impact also out of the domain of the “purely” quantum technologies. We demonstrated in particular, high-sensitive optical detection and transduction of radio-frequency signals (T. Bagci et al., Nature 507, 81 (2014)). This proof-of-principle demonstration has lead to the detection at room temperature of weak electrical rf signals well below the nanoVolt level, and it could lead to relevant applications within the field of Magnetic Resonance Imaging (MRI). This demonstration has also led to a US patent, and the iQUOEMS consortium has already carried out work for improving the efficiency and the bandwidth of such optical detectors of electrical signals.
Further relevant results concerned the realization of wideband microwave amplifiers based on Josephson junction arrays, and the progress for achieving the strong coupling regime of opto-electro-mechanics where a single photon can shift a cavity by more than its linewidth. In this latter case, even though not all the project targets have been reached, we have developed novel solutions which could be applied also within different technological fields. We mention here: i) the development of high-Q membranes made of InGaP, which is a difficult to manage, but very promising, semiconducting material; ii) the realization of nanomechanical membranes with a phononic-badgap isolation stage allowing to reach a world-record quality factor larger than 100 million at room temperature (Y. Tsaturyan et al., arXiv:1608.00937), which has also led to a US patent application; iii) successful inclusion of a superconducting Josephson junction qubit within an electromechanical system, able to boost the effective radiation-pressure interaction between the microwave cavity by six orders of magnitude (J. M. Pirkkalainen et al., Nature Communications 6, 6981 (2015)).
This second group of results, involving signal transduction, fabrication, functionalization, and material issues, shows another important follow-up and visible impact of iQUOEMS. In fact, most of these themes have represented the backbone ideas of two successful programmes funded by the European Commission within H2020: i) the H2020-MSCA-ITN-2016 Innovative Training Network “OMT”, - Optomechanical Technologies; ii) the H2020-FETPROACT-2016-2017 “Boosting emerging technologies” “HOT” –Hybrid Optomechanical Technologies.
The first is an ambitious training network uniting a total of 14 leading groups in the field, two of which two are major industrial players that utilize MEMS and NEMS - Bosch and IBM. Five of the six partners of iQUOEMS are also members of this ITN which has the goal of exploiting optomechanical interactions in views of novel functionality. The envisioned applications include for instance MEMS sensors based on two-dimensional materials like graphene, quantum limited microwave amplifiers, and low noise optical to microwave frequency photon converters. This ITN will provide top-level training to 15 early stage researchers which will also take part to dissemination and outreach activity, with the aim of increasing society’s knowledge about the potentialities of these new technologies.
The second project HOT is an even larger project, involving 17 partners, four of which companies like IBM, Thales, Hitachi and STMicroelectronics, and including four partners of iQUOEMS.
Within HOT, a particular focus will be on nano-optomechanical devices that comprise electrical, microwave or optical systems with micro- and nano-mechanical systems, which represented just one of the relevant demonstrations achieved by iQUOEMS. The 4-years project HOT will explore hybrid opto- and electro-mechanical devices operating at the physical limit for conversion, synthesis, processing, sensing and measurement of EM fields, comprising radio, microwave frequencies to the terahertz domain. Thanks to the close collaboration with companies, we expect to realize realistic applications in the existing application domains of medical (e.g. MRI imaging), security (e.g. Radar and THz monitoring), positioning, timing and navigations (Oscillators). The research aims at specific technological application, with realistic operating conditions and seeks to develop actual system demonstrators. In addition, it will explore how these hybrid transducers can be fabricated within standard CMOS processing, and thereby be made compatible with current manufacturing methods.
iQUOEMS aimed at achieving direct microwave-to-optical conversion also without the intermediation of nanomechanical degrees of freedom, but exploiting directly the electro-optic effect of nonlinear materials. This was an ambitious part of the project which was realized only partially. Nonetheless, the progress made during the time-duration of project has allowed us, and in particular the EPFL partner, to apply some of the ideas to the development of a technology transfer programme which has been also submitted to the FET-Innovation-Launchpad programme. This project, named “Rugged Optical Microresonators (ROM) – Merging Microfabricated Waveguides and Optical Microresonators”, even though not funded, provides in our opinion a good example of the potentialities of the research carried out within iQUOEMS and more in general within the field of hybrid nano-opto-electro-mechanical technologies.