Research at CQE

Radiation sensors down to single quantum limit

High-sensitivity radiation sensing in Finland has been a special focus for years, currently covered by 5 research groups at Aalto. Pushing the sensitivity limits in photodetection is especially important for new and emerging microwave quantum devices that cannot be directly measured using optical methods. Finland has recently demonstrated records, for example, in ultrasensitive fast thermometry and detection of tiny energy packets of microwave photons. These have potential to improve current wireless communications and enable novel quantum communication channels.

Research groups: PICO, NANO, NEMS, PHOTO, QCD.

Quantum metrology and precision measurements

For more than a decade, Finland has made strong efforts in quantum metrology and precision measurements, currently covered by 5 research groups at Aalto. The developments include single-electron current sources realizing the quantum ampere, the emerging standard of electric current. These will be very useful in the calibration of measurement equipment and as integrated components with the other quantum technological systems. In addition to the System of Units that is changing, the definition of the second is evolving and will be based on an optical frequency. Other research efforts in this field include parametric amplifiers, quantum metrology using phase estimation algorithms, and ultra-sensitive magnetometry using qutrits.

Research groups: NANO, KVANTTI, PICO, NEMS, QCD.

Applications of superconducting qubits

Superconducting qubit research has a long tradition in Finland, currently pursued by 6 research groups at Aalto. Although Finland has not yet started a large-scale effort to build a superconducting quantum computer, the research groups have demonstrated successful measurement and control protocols for individual qubits and pursue significant efforts in this direction. The techniques may prove useful in an eventual large-scale quantum computer and other shorter-term applications, such as tunable microwave components. The controlled generation of entangled electron spins is also being pursued based on the splitting of Cooper pairs between a superconductor and normal-state electrodes.

Research groups: KVANTTI, PICO, NANO, NEMS, QT, QCD.

Quantum reservoir engineering and heat management

Open quantum systems and mesoscopic heat transport have been successfully studied in Finland as a pioneering field, which currently includes 6 research groups at Aalto. With the recent rise of electric quantum devices, this basic knowledge has become invaluable for solving several outstanding problems, such as the interplay between dissipation and external control to guarantee extreme precision in quantum control, precise initialization of chosen quantum degrees of freedom, and quasiparticle and local phonon refrigeration. In a large-scale quantum computer, there will be a lot of power dissipated at the chip level which calls for these studies on how to, nevertheless, keep the chip at low phonon temperatures, and how to initialize the quantum degrees of freedom to even lower temperatures than the phonons. Further, the fidelity of quantum sensors could be greatly improved by accurate initialization.

Research groups: PICO, QCD, MSP, QT, Sabrina Maniscalco group, Engineered nanosystems.

Applications of quantum thermodynamics

Although the electrical degrees of freedom are very well in control of current technologies, the precise control of thermal flows and implementation of high-efficiency thermal engines has lagged behind greatly. The solution to this problem is to be found at the nanoscale, a subject where Finnish researchers have recently excelled in the thermodynamics of small electrical systems, covered by 5 research groups at Aalto. This is an exceptional knowledge base to implement quantum thermodynamic systems and engines. The potential applications are the realizations of high-efficiency heat engines working at low-temperature gradients and efficient energy-harvesting devices.

Research groups: PICO, QT, MSP, Erik Aurell group, Engineered nanosystems.

Topological materials

Topology is a very powerful tool to describe the qualitative behavior of physical systems and provides the foundations for a topological quantum computer. Topology in condensed matter quantum systems has been studied for several decades in Finland, starting from the pioneering work on superfluid helium in rotation and continuing to directions with promising future applications, such as flat-band high-temperature superconductivity. Recently, there has been breakthrough theory work in Finland discovering a connection between flat-band superfluidity and quantum geometry, connecting superfluid weight with the Chern number. Currently, there are 4 research groups at Aalto working on topological materials and defects.

Research groups: NANO, QD, ROTA, QCD.

Quantum key distribution, quantum randomness, and random number generation

Currently, quantum key distribution is being developed in 2 research groups at Aalto. The activities include, for example, calibration methods for quantum efficiency of sources and receivers. In addition to quantum key distribution, quantum random number generators have already found their way to commercial markets.

Research groups: PHOTO, MQS.

Light-matter interface and quantum optics in nanoscale

Currently, quantum optics is undergoing great miniaturization from optical tables into micro- and nanoscale waveguides on a chip. Such development is required for mobile commercial products and to implement robust utilization of the multidimensional Hilbert space. The bottleneck here is the introduction of photon–photon interactions, which calls for light-matter interfaces. These interfaces can also be used to mediate highly complex quantum states, which can be engineered in solid-state quantum processors, to optical photons and back. Another important line of research is lasing and condensation phenomena in nanoplasmonic systems, offering new types of quantum fluids with applications as coherent nanoscale light sources with low energy consumption, for instance. Some of the key applications include precision measurements with light and quantum repeaters to extend the range of true quantum-safe key distribution. Currently, there are 5 research groups at Aalto working on these topics.

Research groups: QD, NANO, NEMS, PHOTO, MQS.