QUEST Excellence Cluster gets underway

Research on the quantum limit begins

May 23, 2008

Today, on 23 May 2008, the Hannover QUEST Excellence Cluster (Center for Quantum Engineering and Space-Time Research), has officially started its work. In the four areas of quantum engineering, quantum sensors, space-time research and novel technologies, around 60 new scientists will be involved in the coming five years, in addition to the 190 already pursuing research on the quantum limit.

Area “quantum engineering”

The new possibilities for the manipulation of light and matter, which are described by the term “quantum engineering”, have revolutionized nuclear physics and quantum optics in recent years. A completely new range of parameter areas has thereby been opened up by these fields of research: just as the coherent (connected) light waves of the laser light can also be described as a current of numerous light particles or light quanta – so does a particle stream of extremely cold atoms (cooled down to ca. -273° C by means of laser cooling, thereby reaching a temperature near that of absolute zero) increasingly take on the character of a coherent wave of matter as the temperature drops.

So-called atomic lasers thereby enter the realm of the conceivable. These would emit material waves with laser-like properties. This opens an entirely new range of applications in so-called atomic optics - like the laser in optics - in quantum optics, both in fundamental research as well as in innovative technical applications.

Quantum engineering therefore constitutes its own major research area in QUEST. This field forms the basis for other research areas and innovations in the Cluster of Excellence. These include, for example, innovative quantum sensors, the next generation of optical atomic clocks, in which the “pendulum” oscillates at the rate of light frequency (about 1015 Hz), next-generation gravitational wave detectors and innovative precision measuring devices for geodesy.

In this sense, quantum engineering provides a workbench for hammering out new ideas for driving research in these fields, to explore its physical boundaries, and particularly to investigate new, far more complex and coupled quantum phenomena. The experimental and theoretical methods of different disciplines are brought together here to create new control mechanisms for quantum systems.

The “quantum sensors” area

Such control is the prerequisite for the development of next-generation quantum sensors. In the field of “quantum sensors” the development of new gravitational wave detectors, optical frequency standards, and atomic clocks, as well as inertial sensors with light and material waves are planned.

The three currently operational gravitational wave observatories, LIGO (US), Virgo (Italian-French) and GEO600 (German-British) are the most sensitive detectors for the measurement of length differences ever created. The length change in the two arms of the detectors is measured by a high-precision laser interferometer. In GEO600, the gravitational wave detector in Ruthe, south of Hanover, the next-generation technology has already been tested and used.

To make further progress in this area, QUEST is already working intensively on new light sources that use a special form of light - “squeezed light” - to reduce light-based noise to a level below the so-called quantum noise limit. This research area has also given rise to the necessary developments for the space-borne gravitational wave detector “LISA”, which was conceived under the scientific leadership of the Albert Einstein Institute in Hannover. Atomic optics have the potential to provide atomic clocks with the capacity for such unimaginable accuracy that they deviate measurably from one another when separated by only one centimetre in height above the laboratory table, due to the relativistic redshift in the gravitational field of the earth. This research work in QUEST gives rise to highly interesting application possibilities in geodesy, which can thereby measure the geoid (potential of the earth's gravity) precisely with the help of these extremely precise atomic clocks.

On the other hand, new atomic interferometers are being designed and built in QUEST that, as highly precise inertial sensors, will far surpass the best “classical” acceleration and rotation sensors. These sensors will be used in outer space to research the free fall of different masses, especially on the quantum level with various elements or isotopes, in order to investigate the so-called equivalence principle more precisely. This could provide the first clues for a theory of the yet unexplored quantum gravitation. Pursuing the same aim, QUEST is seeking to check the consistency of natural constants by comparing highly precise atomic clocks, which are each operated with different isotopes as atomic reference points.

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