Current developments in the field of quantum sensing, communication and computation are expected to have major social impacts, and could for example lead in the near future to improvements of the navigation systems reliability, increase in the computing power or enhancement of the communications security. The research topics at imo-imomec/imec quantum Science and Technology (QST) division span over different quantum technology domains, with a particular focus on solid-state spin qubits in diamond and other wide-bandgap materials.
The last years have seen a rapid evolution of quantum technologies, from basic physics concepts to practical applications. The current developments observed in the field of quantum sensing, communication and computation are expected to have major social impacts, and could for example lead in the near future to improvements of the navigation systems reliability, increase in the computing power or enhancement of the communications security. Solid-state qubits, consisting in defects with associated electron or nuclear spin in solids, enable the realisation of long-lived quantum memories, the manipulation and readout of quantum states, as well as their optical transmission. Compared to other physical systems (e.g. superconducting circuits or trapped ions), solid-state defects enable the realization of scalable and electronic-compatible arrays, using well-developed solid-state device engineering techniques. They are thus among the most promising candidates for the realization of quantum technologies
The research topics at imo-imomec/imec Quantum Science and Technology (QST) division span over different quantum technology domains. Our work is focussed on the intersection between the fields of quantum optics and nanoscale solid-state physics, and in particular on solid-state qubits integrable with classical electronics in wide-bandgap materials. These qubits have the advantage of operating at room temperature, easing industrial applications as well as integration and scaling-up. Our research is specially centred on spin defects qubits in diamond, in which the longest electron spin coherence times have been demonstrated (~ 2 ms for nitrogen-vacancy – NV – centres electron spin at room temperature). Our activities range from the fabrication of quantum-grade diamond, the engineering of spin defects in diamond and the advanced characterisation of these defects optical, photoelectric, and spin properties to the development of diamond-based devices for quantum sensing, quantum communication and quantum information processing. We also study novel point defects in wide-bandgap materials such as diamond, which allow operation as single photon sources or non-classical, entangled photon sources. A significant part of the our research is dedicated to the implementation of photoelectrically read-out qubits in diamond, a field of research that was initiated in our group.
The Q-Lab, Quantum Hardware, Quantum Communication, and Quantum Realization groups partake in several priority EU calls in the field of quantum technologies, including the Framework Partnership Programmes (FPA) with industries. In addition, we participate in Quantum Communication calls within the EURO-QCI project, teaming with other Belgian and international partners to build secure quantum communication networks in Belgium and in Europe, as well as in national quantum communication projects. Finally we are strongly engaged in EU quantum computing calls, such as European High-Performance Computing (HPHC) Joint Undertaking, within which we partake in building a quantum computer network in the EU. In this framework, six quantum computers will be built in EU countries, connected to classical supercomputer infrastructure. At the same time, the QST group represents Belgium to Quantum Flagship activities, being part of the QCN 27 EU countries directory board.
The use of solid-state spin defects as qubits for quantum applications requires long spin coherence times (defined as the maximum duration a system can remain in a prepared quantum state). This coherence time is limited by the interaction of spin qubits with the magnetic noise resulting from the surrounding electron and nuclear spin bath. The quality of the host material is thus an essential factor for the development of high performance solid-state qubits.
Based on our recognized expertise in the field of diamond synthesis by plasma enhanced chemical vapour deposition (PECVD), we work on the development of quantum-grade diamond, presenting ultra-high isotopical and structural purity compared to commercially available materials. This work involves the optimization of PECVD reactors and epitaxial growth parameters for the preparation of high-quality single crystal diamond layers.
Another objective is the formation of spin defects with controlled density, depth, charge state and coherence time by in-situ doping during PECVD. The properties and location of color centres in the diamond crystal can be engineered, for example through co-doping with different atoms or by etching and selective CVD overgrowth of diamond. Our research is particularly focused on the fabrication of doped single-crystal materials presenting optimal properties for the photoelectric readout of spin states. In parallel, we also investigate the seedless PECVD growth of doped nanodiamonds presenting high crystal quality, controlled size and long T1 spin coherence times, which are required for nanoscale quantum sensing especially in biological environment.
The optimization of the host material quality, as well as the study of the spin defects formation mechanism and the assessment of their quantum properties is based on the feedback of in-house characterization of structural, optical, photoelectric and spin properties by various advanced techniques including SEM, AFM, confocal microscopy, photoluminescence and photocurrent spectroscopy, time of flight and spin coherence measurements.
The development of photoelectrically readout solid-state qubits is one of the main activities of Imo-imomec QST division. Based on the group expertise in the field of defects photophysics, a method enabling the photoelectric detection of NV centres magnetic resonances (PDMR) was first demonstrated at Imo-imomec in 2015. It was since then further developed and optimized, enabling the photoelectric readout of coherently driven single electron and single nuclear spins. Based on the direct detection of free charge carriers resulting from color centres photoionization, this method does not require any complex collection optics and allows integration of the measurement circuitry directly on the diamond, thus bringing the quantum platform to an electronic chip. It also enables the spatially-resolved detection of single spins, with improved spatial resolution compared to optical detection.
From a fundamental point of view, the research currently performed on PDMR aims at better understanding the physical processes involved in spins photoelectric readout. This work includes the experimental study of color centres photophysics and ionization mechanisms using various sensitive spectroscopy techniques, the characterization of the diamond material electronic properties and the mathematical modelling of PDMR. The objective is, on the one hand, to further improve the photoelectric readout of NV centres spins in diamond and, on the other hand, to extend the PDMR method to different spin defects in diamond (e.g. group IV-Vacancy defects or Ni-associated defects) and to color centres in other wide-bandgap materials, especially silicon carbide.
From a technical point of view, current challenges include the fast detection of ultra-low photocurrents (to make the photoelectric readout compatible with pulsed protocols used for spin manipulations), the independent readout of adjacent micrometric sets of electrodes and the minimization of the technical noise (due in particular to cross-talks between the microwave field used for spin manipulations and the photocurrent detection path). Our work aims thus at improving all components of the diamond chip, including electrodes, interconnectivity of the wire circuits on the diamond chip with the external control and readout electronics, and current amplifiers and detectors.
Quantum sensors, in which the influence of external parameters on quantum superposition states is detected, have the potential to reach ultra-low sensitivities. Solid-state magnetometers based on ensembles of NV centres spins in diamond are among the most developed quantum sensors, with the first integrated devices being expected to become commercially available within the next ten years. They enable the detection of sub-picoTesla magnetic fields with high dynamic range and bandwidth, and could find applications in the fields of automotive, space, failure analysis or magnetic field sensing in biological environment.
The QST division at Imo-Imomec works on the development of photoelectrically readout NV diamond sensors, for magnetic field sensing and microwave detection. Compared to optically readout systems, these sensors could present improved sensitivities and higher compactness, as well as an easier integration with electronics. One of our objectives is the development of architectures and protocols enabling the parallel addressing of adjacent micrometric pixels, to form spatially-resolved photoelectric quantum sensors. In parallel, we develop fully integrated compact magnetometers, containing all required components, from the control and readout system to magnetic, microwave, radio-frequency, and optical manipulation tools. This type of miniaturized device is of a high interest for scientific space missions, Earth magnetic field measurements for geological exploration, satellite navigations or monitoring of space weather.
Our research aims in particular at improving the sensitivity of photoelectrically readout diamond quantum sensors, by maximizing the NV centres charge state purity and the spin initialization fidelity, minimizing the background photocurrent and improving the charge carriers collection efficiency. Achieving these goals requires to better control the NV centres environment, to improve the diamond-electrode interface and to optimize experimental parameters. Protocols are also developed to make the photoelectric readout compatible with high-frequency AC quantum sensing.
In parallel, we investigate the use of nanodiamonds containing color centres for nanoscale temperature sensing in biological environment.
An example of quantum sensor applications is project OSCAR-QUBE, which was a demonstration of NV based quantum magnetometer sensor tested aboard the International Space Station.
Recent progress in the field of quantum sensing has demonstrated the possibility to use NV centres diamond spin qubits to detect external nuclear spins in close proximity, allowing thus nanoscale NMR at room temperature. Compared to classical NMR devices, these diamond quantum sensors enable to perform spectrally selective detection on small volumes (~ 1 pL), and do not require the applications of strong, homogeneous magnetic fields and thus the use of bulky magnet. Miniaturized quantum NMR devices could in particular be used in the pharmaceutical industry, for drug discovery and drug product development.
The QST division at Imo-Imomec works on demonstrating the practical applicability of nanoscale quantum NMR detection, by bringing it from the lab table towards real-world applications in the field of pharmaceutical analysis. Our objective is the development of novel types of quantum NMR devices based on 2D arrays of shallow NV centres in diamond. While current methods are based on the optical readout of NV spins, we aim at developing photoelectrically readout quantum NMR devices. The use of this method is expected to improve the detection sensitivity and thus to lead to faster measurements, enabling to perform dynamical detection in biological or chemical environment with high signal-to-noise ratio.
Current research on quantum communication is motivated by the need for encryption methods which cannot be broken by quantum computers, contrary to classical encryption. The development of quantum networks could lead to applications such as enhanced sensor networks or distributed quantum computing. To enable communications over large distances, quantum networks require the presence of quantum repeaters, allowing the distribution of quantum states and information between entities without direct point-to-point connections.
The QST division at Imo-Imomec studies the development of quantum memories that could be used as outer nodes for quantum communication networks. We investigate in particular memories based on NV centres in diamond, presenting the longest memory coherence properties at room temperature and for which we already established the photoelectric readout of a single nuclear spin coupled to an NV electron spin. However, other point defects in diamond - in particular group IV-vacancy defects, presenting better optical properties - are also considered for this application.
Another axis of our work deals with ultra-low-noise light detection methods, for application in the field of gravitational waves detection. Theoretical studies aiming at the mathematical description of light quantum detection (in particular squeezing and entanglement-based method) are performed, and an experimental setup enabling the production of squeezed light and the heterodyne detection of light is developed. We investigate in particular the suppression of quantum noise by using spin-optomechanical hybrid systems based on ensembles of nuclear spins in diamond.
Quantum computers, based on the encoding of information on the superposition states of qubits, act as massive parallel devices. This specificity leads to hugely enhanced computation power compared to classical computers, which could enable to address problems that cannot be solved using current technologies.
The greatest challenge to construct a quantum computer is the technology scale-up, to reach computers with thousands of qubits. The currently used superconducting qubits are operated at cryogenic temperature, making any scaling up complex and costly in terms of energy, space and cooling power. The photoelectrically readout diamond qubits developed at Imo-Imomec could facilitate this upscaling, by enabling the fabrication of qubit arrays in the form of nano-electronic chips operated at ambient conditions and easily integrated with classical electronics.
We already demonstrated the possibility to perform the photoelectric readout of a single quantum gate made of an individual nuclear spin coupled to an NV centre electron spin. Based on this achievement, we currently work on optimizing the fidelity of photoelectrically read gates and on the application of the photoelectric readout method to more complex gate sequences, opening the possibility for the realizations of small solid-state quantum processors. By downscaling the size of the electrodes fabricated on the diamond crystal, we could also reach the site-resolved readout of dipole-dipole entangled NV qubits, thereby realize nanoscale coupled registers.
The Interreg project E-TEST is a very important step of the Einstein Telescope, as it will be a proof of concept, both on the prototype side and on the geological side.
ET-pathfinder involves the construction of a state-of-the-art R&D facility for interferometry with flexible high-tech laser setups.
Microwave generation and detection equipment is nowadays included in almost every piece of electronics. Microwave spectral analyzers suitable for novel generation of 5G and future 6G networks ...
AMADEUS (2022-2026) is an industry-led consortium, funded in the framework of the Quantum Technologies Flagship to develop miniaturized, integrated, transportable quantum sensors based on nitrogen-vacancy (NV) centers in diamond ...
The realization of small to medium-scale, integrable and portable quantum processors operating at ambient conditions represents a major technical challenge. The MAESTRO project aims at proposing a novel approach for the realization of small quantum processors ...
Nuclear Magnetic Resonance (NMR) spectroscopy is widely used by pharmaceutical companies in the process of drug discovery and drug product development ...
Hasselt University has built a significant expertise in room temperature quantum measurements on diamond spin defects. However, cooling down the solid-state spin system offers the opportunity to explore numerous physical phenomena and new applications ...
The SBO project BeQuNet (2022-2024), based on a collaboration between Belgian universities and research technology organizations, and in close cooperation with local industrial partners, aims at establishing the first Belgian quantum network ...
The objective of this four-year FWO project (2019-2023) is to use ab-initio modeling to theoretically predict and design a novel type of solid-state spin defects made of group IV (Si, Ge, Sn, Pb) – vacancy complexes (XV complexes) in diamond ...
Hasselt University has developed a photoelectric method for the readout of solid-states spin qubits in diamond. Based on the detection of free charge carriers resulting from color centres ionization, this method involves ...
The implementation of highly entangled quantum states is at the basis of most quantum technologies in the area of quantum computing, quantum simulation, quantum sensing or quantum communication ...
All gravitational waves detectors are based on Michelson interferometers. Increasing the sensitivity of these detectors requires to minimize the noise in the output signal of the optomechanical system constituted by each of the arms of the interferometer combined with an end mirror ...
OSCAR-QUBE is a student project aiming at development of a portable quantum diamond magnetometer for space applications. The resulting device was tested for nearly a year aboard International Space Station (ISS).
The expertise of the photonics and quantum lab ranges from the characterization of wide-bandgap materials and the fundamental study of color centres excitation and ionization mechanisms to the development of photoelectric spin readout methods, the study of solid-state qubits based on electron and nuclear spins and the development of quantum sensors and quantum memories. In collaboration with the wide-bandgap materials group of Imo-imomec, we operate several PECVD diamond growth reactors dedicated to the synthesis of ultra-pure and doped diamond. The photonics and quantum lab houses various home-built sensitive setups, used for the characterization of materials optical and photoelectric properties. It comprises in particular five confocal photoluminescence setups, designed for the in-depth characterization of color centres in wide-bandgap materials. All confocal setups are equipped for the characterization of spin qubits and allow the parallel detection of optical and photoelectric signals, enabling the development of optically and photoelectrically readout quantum devices.
Various sensitive home-built setups are used for the in-depth characterization of wide-bandgap materials optical (photothermal deflection spectroscopy, photoluminescence spectroscopy, photoluminescence excitation spectroscopy), photoelectric (photocurrent spectroscopy) and electronic (time of flight) properties.
Confocal photoluminescence microscopes are built on air-stabilized optical table and equipped with single photon detectors, high resolution piezoelectric stages and high numerical aperture microscope objectives, enabling the study of single color centres in insulating materials. Lasers of different wavelengths, from blue to near-infrared, are available for photoexcitation, allowing the study of a wide range of color centres in various wide-bandgap materials. The lab is in particular equipped with a state-of-the-art tunable laser, emitting from green to near-infrared, and enabling the study of defects excitation and ionization dynamics, for example by the simultaneous recording of photocurrent and photoluminescence excitation spectra. A setup enabling the characterization of samples at liquid helium temperature is under construction.
The different confocal setups are equipped with acousto-optic modulators (AOM) for light pulsing, with arbitrary waveform generators (AWG) and with fast electronic cards, enabling the application of advanced pulse sequences used for the characterization of spin coherence times (T1, T2, T2*), for the manipulation of quantum gates and for quantum sensing applications. All confocal setups allow the optical (single photon detectors) and photoelectric (stable voltage sources, sensitive current preamplifiers, lock-in amplifiers) readout of spin qubits. A calibrated setup is specially designed for quantum magnetometry applications.
Custom-built, our characterization setups can easily be adapted for different experiments and applications.
We collaborate with research groups and industrial partners specialized in the synthesis of widebandgap materials (in particular diamond) or in the implantation of color centres in these materials, and willing to evaluate the material quality, as well as the defects optical and spin properties. We also have multiple collaborations with other theoretical and experimental research groups working in the field of solid-state qubits development and quantum applications.