Enabling Technologies

The second quantum revolution builds on the technologies and processes that the first quantum revolution has developed and continuously optimized over the last few decades. Laser systems play a central role in quantum technologies. Looking at the subsystems and components used, it becomes clear that, without photonic enabling technologies, it would be practically impossible to control, manipulate or measure individual quanta – be they photons, ions, electrons or atoms – or to observe their behavior.

The aim is often to bring quanta within a defined distance of micrometers so that they (or, in the case of atoms and molecules, their electrons) can interact with each other. This requires high-precision, stable lasers and optics that direct their beams to the respective focal points with micrometer precision. Lasers are used to ionize neural atoms and molecules. This makes it possible to capture and fix them electromagnetically. Alternatively, magneto-optical traps are used. Here, lasers cool neutral particles to an extreme extent in order to slow them down. As a result, they can be precisely positioned in a magnetic field for experiments and measurements, while lasers also record the forces, frequencies and other dynamics. Laser pulses can also be used to generate quantum mechanical superpositions from two states or to set quanta in rotation in a controlled manner. Process monitoring is often also based on photonics, forexample with camera-based detection of emitted photons or laser-based fluorescence measurements.

Nobel Prize technologies as enablers

Numerous research teams have developed the basic principles and have received more than one Nobel Prize in Physics for their work. These include the group led by Steven Chu, who came up with the idea of slowing down atoms using laser cooling. Lasers can cool atoms or ions in gases to a few millionths of a degree above absolute zero in a fraction of a second. This reduces their speed from hundreds of meters per second to just a few centimeters. When slowed down in this way, they can be controlled in optical gratings or with the help of laser-optical tweezers, which can be traced back to research by Arthur Ashkin, who also won a Nobel Prize.

In order to measure ultra-high frequencies in quantum systems, femtosecond lasers, very stable continuous wave lasers and optical frequency combs are used; Nobel Prize-winning groups led by Donna Strickland and Gérard Mourou as well as by Theodor W. Hänsch contributed significantly to the development and procedural application of these technologies. In addition, various methods of spectroscopy and microscopy as well as camera systems are used to observe and measure the modes of action and processes in quantum systems, which have won Nobel Prizes over the last 100 years.

Then there are the optical building blocks of the quantum systems. These include single photon sources and detectors as well as optics specifically designed for the respective system. There are also aspheres, free-form optics and micro-optics as well as highly complex lens and mirror cascades, beam splitters and deflectors, which direct the laser beams – sometimes with sub-micrometer precision – to where the individual quanta have to be controlled and manipulated or where the quantum mechanical processes have to be read out. In view of the precision, the low light intensities and the frequencies measuring up to the gigahertz range, high-end photonic components are required that ensure optimum beam shielding, minimize scattering losses, enable almost noise-free optical signal processing and provide laser beams that can be focused very sharply.

Quantum technologies are a growth market for photonic enablers. According to market analyses, they currently sell systems, components and subsystems worth around EUR 200 million annually. This volume is set to rise to more than EUR 500 million per year by 2030.