Periodic Reporting for period 2 - BRISQ (Brisk Rydberg Ions for Scalable Quantum Processors)
Reporting period: 2023-10-01 to 2025-09-30
The EU-funded BRISQ project set out to explore how future quantum computers could run extremely long and complex calculations, far beyond what is possible today. Its overall aim was to lay the foundations for a quantum computing prototype capable of executing quantum algorithms with more than one million computational steps. Reaching such depths would represent a major advance in quantum information processing and simulation. In the long term, this could benefit applications where quantum computing is expected to play an important role, such as the design of new materials and pharmaceuticals, or the solution of complex optimization problems that require very deep calculations.
BRISQ focused on a novel technological approach based on trapped ions excited to very high-energy electronic states, known as Rydberg states. These so-called Rydberg ions interact strongly with each other over relatively long distances. A key advantage of this platform is that quantum information can remain stable for very long times - up to seconds - while quantum operations between ions can be carried out extremely quickly, within about 100 nanoseconds. This combination of long stability and fast operations is essential for enabling very deep and complex quantum computations.
At the start of BRISQ, research on Rydberg-ion quantum devices was being carried out in only two laboratories worldwide, both located in Europe. One partner in the BRISQ consortium had already demonstrated the first ultra-fast entangling operation using this approach, giving Europe a strong and unique position in developing this emerging technology. BRISQ built on this foundation by strengthening and expanding the scientific and technological basis of the platform.
To achieve its goals, BRISQ brought together a consortium of experimental and theoretical academic research groups alongside industrial partners. This broad range of expertise made it possible to address the challenge from many directions, from developing scalable and industry-compatible hardware to designing quantum algorithms and software tools tailored to this new technology. Together, these advances contribute to the long-term development of powerful quantum simulators and open new possibilities for applications such as the simulation of physical systems and, potentially, quantum chemistry.
BRISQ focused on a novel technological approach based on trapped ions excited to very high-energy electronic states, known as Rydberg states. These so-called Rydberg ions interact strongly with each other over relatively long distances. A key advantage of this platform is that quantum information can remain stable for very long times - up to seconds - while quantum operations between ions can be carried out extremely quickly, within about 100 nanoseconds. This combination of long stability and fast operations is essential for enabling very deep and complex quantum computations.
At the start of BRISQ, research on Rydberg-ion quantum devices was being carried out in only two laboratories worldwide, both located in Europe. One partner in the BRISQ consortium had already demonstrated the first ultra-fast entangling operation using this approach, giving Europe a strong and unique position in developing this emerging technology. BRISQ built on this foundation by strengthening and expanding the scientific and technological basis of the platform.
To achieve its goals, BRISQ brought together a consortium of experimental and theoretical academic research groups alongside industrial partners. This broad range of expertise made it possible to address the challenge from many directions, from developing scalable and industry-compatible hardware to designing quantum algorithms and software tools tailored to this new technology. Together, these advances contribute to the long-term development of powerful quantum simulators and open new possibilities for applications such as the simulation of physical systems and, potentially, quantum chemistry.
BRISQ carried out a coordinated programme of experimental, theoretical, and technological research covering all essential building blocks of a scalable quantum computer based on Rydberg-excited trapped ions.
On the hardware side, the project designed, fabricated, and tested ion-trap devices optimized for Rydberg excitation using industrially compatible fabrication techniques. Cryogenic systems were implemented to ensure stable performance and to reduce unwanted disturbances that can disrupt quantum calculations. The project also developed and tested two-dimensional trap designs, which are an important step toward building larger and more powerful quantum computers.
The team developed advanced techniques to control individual ions with high precision. These included robust multi-pulse schemes and high-resolution laser addressing methods, which improve the accuracy and reliability of quantum operations, even in the presence of small experimental imperfections.
A central achievement of BRISQ was the development of fast and high-fidelity quantum gate protocols based on Rydberg interactions. The project created detailed theoretical models to understand how these systems behave and used this knowledge to design practical gate schemes that can operate on nanosecond timescales with very high fidelity.
BRISQ also looked beyond basic two-ion operations. It studied ways to control several ions at once to make quantum computations more efficient and explored how the natural vibrations of the ion system can be used as an extra resource for simulating complex physical systems. BRISQ studied how such advantages can be effectively realized on the Rydberg-ion platform.
In addition to hardware and control, BRISQ worked on the software needed to run quantum computers reliably. The project developed tools to help detect and correct errors during calculations and created methods to translate high-level quantum algorithms into instructions that the Rydberg-ion hardware can carry out efficiently. Together, these advances lay important groundwork for future large-scale and reliable quantum computers.
On the hardware side, the project designed, fabricated, and tested ion-trap devices optimized for Rydberg excitation using industrially compatible fabrication techniques. Cryogenic systems were implemented to ensure stable performance and to reduce unwanted disturbances that can disrupt quantum calculations. The project also developed and tested two-dimensional trap designs, which are an important step toward building larger and more powerful quantum computers.
The team developed advanced techniques to control individual ions with high precision. These included robust multi-pulse schemes and high-resolution laser addressing methods, which improve the accuracy and reliability of quantum operations, even in the presence of small experimental imperfections.
A central achievement of BRISQ was the development of fast and high-fidelity quantum gate protocols based on Rydberg interactions. The project created detailed theoretical models to understand how these systems behave and used this knowledge to design practical gate schemes that can operate on nanosecond timescales with very high fidelity.
BRISQ also looked beyond basic two-ion operations. It studied ways to control several ions at once to make quantum computations more efficient and explored how the natural vibrations of the ion system can be used as an extra resource for simulating complex physical systems. BRISQ studied how such advantages can be effectively realized on the Rydberg-ion platform.
In addition to hardware and control, BRISQ worked on the software needed to run quantum computers reliably. The project developed tools to help detect and correct errors during calculations and created methods to translate high-level quantum algorithms into instructions that the Rydberg-ion hardware can carry out efficiently. Together, these advances lay important groundwork for future large-scale and reliable quantum computers.
BRISQ delivered important advances beyond the state of the art by establishing a credible pathway towards realizing a trapped-ion quantum computing platform that combines long coherence times and ultra-fast gate speeds. The project developed and validated improved theoretical gate schemes and identified experimentally realistic parameter regimes to enable fast and accurate gate operations.
In parallel, BRISQ built and characterized the key technological foundations required to realize such gates experimentally. These included scalable and industrially compatible ion trap hardware, cryogenic operation, advanced control techniques, and two-dimensional trap architectures suitable for future large-scale systems. Together, these results demonstrate how ultra-fast quantum operations and long-lived quantum information can be integrated into a single, scalable platform.
BRISQ advanced Rydberg-ion quantum computing from an early-stage research concept to a well-defined, technically grounded platform supported by scalable hardware designs, robust control methods and high-performance gate protocols. These developments are an essential step towards fault-tolerant quantum computation and clearly identify the remaining challenges for experimental demonstration.
Further progress will require the experimental realisation of the proposed gate schemes and quantum error correction protocols, as well as scaling up to larger ion arrays. The outcomes of BRISQ provide a solid foundation for follow-up research, technology maturation and potential Pathfinder-to-Transition activities, which are aimed at demonstrating high-fidelity operation in increasingly complex quantum systems.
In parallel, BRISQ built and characterized the key technological foundations required to realize such gates experimentally. These included scalable and industrially compatible ion trap hardware, cryogenic operation, advanced control techniques, and two-dimensional trap architectures suitable for future large-scale systems. Together, these results demonstrate how ultra-fast quantum operations and long-lived quantum information can be integrated into a single, scalable platform.
BRISQ advanced Rydberg-ion quantum computing from an early-stage research concept to a well-defined, technically grounded platform supported by scalable hardware designs, robust control methods and high-performance gate protocols. These developments are an essential step towards fault-tolerant quantum computation and clearly identify the remaining challenges for experimental demonstration.
Further progress will require the experimental realisation of the proposed gate schemes and quantum error correction protocols, as well as scaling up to larger ion arrays. The outcomes of BRISQ provide a solid foundation for follow-up research, technology maturation and potential Pathfinder-to-Transition activities, which are aimed at demonstrating high-fidelity operation in increasingly complex quantum systems.