Quantum physics – the principle “both and”

It is not really understandable, but we still hold your applications every day: quantum physics and its technical use. As one of the main columns of modern physics, quantum physics describes the behavior of the smallest physical objects such as molecules, atoms or elementary particles. The classical physics, which our macroscopic world describes, for example, about the sub -areas of mechanics, electrodynamics or thermodynamics, cannot explain this “microscopic” systems. A hundred years after the first mathematical wording for the description of the quantum world, in the »International Quantum Year 2025«, back and outlooks are held on the physical and technical achievements of the discipline.

The first approaches to the development of quantum physics came in 1900 by Max Planck, who realized that the heat radiation of a body could not be described with classical physics. Planck postulated that the energy exchange between the matter of the body and the electromagnetic field did not continuously take place, but only “quantified”.

The quantums also helped with the model description of atoms: in early representations, the negative electrons “like raisins” were distributed in a positively charged “dough”. While such a “rosin cake model” after Joseph Thomson was able to present certain observations well, it remained owe to an explanation: the frequencies that are characteristic of a certain atom for the cause of spectral lines, the light of discrete frequencies.

With the nuclear model of Niels Bohr (1913), electrons in the atom were first placed on stable orbits. If the electrons jumped between the individual lanes, a very specific, discrete energy was absorbed or handed over as light quantity.

With the wording of quantum mechanics in 1925, largely developed by Erwin Schrödinger, Werner Heisenberg, Max Born, Paul Dirac, Wolfgang Pauli and Pascual Jordan (his political involvement in National Socialism today is the reason that he was the only co -founder of the quantum mechanics not to be a Nobel Prize ), then a mathematical wording was available, which could correctly describe the physical properties of light and the smallest matter particles.

But also provided with this mathematical operating instructions, the smallest particles still provide great headaches, most quantum phenomena can hardly be compared to everyday processes.

An object exists in
several states at the same time

For example, the principle of “overlay” states that a quantum object can exist in several conditions (a “yes and no”); Only the physical measurement ensures certainty. The fact that such a consideration cannot be transferred to our macroscopic world was impressively described by the popular thoughts of thoughts “Schrödinger’s cat” (roughly: a cat is both lively and dead – until someone carries out a measurement …).

And also with “wave particle dualism”, an object, such as an electron, shows itself from its multi-layered side. For example, electrons behave on the one hand as the term “elementary particles” suggest (for example, if they are in an electron tube in exactly one place), on the other hand, they show in the famous double gap experiment that they can also behave like a wave if They present an interference pattern to the astonished or quantum -mechanically enlightened viewer, as is only known from waves.

With the “International Year of Quantum Science and Quantity Technologies 2025”, you not only look back on the first 100 years of quantum physics worldwide, but also take a look into the future. In 57 countries, numerous actions and lecture series are offered, which want to bring the ubiquitous use of quantum technologies closer to everyone. In Germany, the campaign year is coordinated by the German Physical Society, which under the motto “Hundred years are only the beginning …” and rejoices.

Because the “beginning” makes life very comfortable in many areas.

Quantum physics is in
our everyday technical life

In the car (or the GPS), the navigation system uses the unsurpassed precision of atomic clocks based on the discrete transitions of the electrons in the atom: The GPS receiver measures the times it needs to receive signatures of four different satellites, to determine his position as precisely as possible. Only through the extremely precise time measurement is the necessary accuracy in the position (around five meters for GPS-capable smartphones) in order not to be recorded in the rear-view mirror.

And if you buy a DVD at the cash register, you are looking forward to laser, which use the quantum-mechanical concept of the “stimulated emissions” of photons in atoms: barcode scanner or DVD laser (also for CDs) touch the data traces without contact AB, which are then converted into an electrical signal.

If the film played in this way, this could then look at this via the magnetic resonance imaging (MRI): the magnetic spin resonance, also a phenomenon of quantum physics, allows the structure and function of organs and tissues in the body very much, as part of medical diagnosis to be shown in detail.

Most quantum phenomena can hardly be compared to everyday processes.

And there is even more in (not only in the body, also for quantum mechanics): transistors, presented for the first time in 1947 and recognized with the Nobel Prize nine years later, or solar cells as semiconductor elements, CCD sensors for the digital camera, as well as the Flash memory or the raster tunnel microscope.

The latter is based on the quantum mechanical “tunnel effect”, after which particles can overcome a barrier (“tunnel”), although their energy is actually far too low. Here, too, an attempt at description of classical physics hardly helps – because those who want to “want their heads through the wall” may have a broken bone in the classic world – and only in the quantum world their impressive breakthrough.

Scientists then hope for a real breakthrough on numerous, still quite young areas of quantum physics, for example in quantum cryptography or quantum computing.

Safe encryption
with quantum cryptography

Originally, cryptography aims to encrypt information safely, so that only the transmitter and addressee have access to sensitive content. Today, the “science of secret writing” is being grasped a little further and includes aspects of data security, such as a change or counterfeiting protection. Quantum cryptography develops extremely secure methods in order to transmit the key to the (de) coding of the message exclusively to the rightful participants. If a curious third party tries to intercept the key, he has to carry out a kind of measurement: the previously overlaid state “decides” for a condition. This can recognize the listening attempt, canceled the data transmission and tried with a new key.

Security is therefore based on the laws of quantum mechanics and not on mathematical algorithms – of which the most stubborn listers always hope to be able to crack them.

In quantum computing, too, the overlap is used: instead of bits, a sequence of zeros and one, quantum computers work with quantum bits. Those units called “Quibits” can now represent both “zero” and “one”, which enables a parallel instead of the usual sequential (one after the other). Today, classic supercomputers such as “El Capitan” with a computing power of 1,742,000 teraflops – but messages like that of Google’s “QuanteCHIP Willow”, which, according to the group, need a calculation for normal supercomputers “longer than the age of the universe If «, done in five minutes, if a significant progress marked. In the case of error correction, which has so far severely limited the actual use of quantum chips (quantum states are extremely prone to interference), significant progress has also been made.

Quantenphysikalisches
Experiment with a negative period of time

Scientists recently came up with another amazing effect of quantum physics: they were able to show that photons that are blasted by clouds of rubidium atoms stimulate them as expected – but have long been emitted again before the atom has passed into its basic state. It turned out that the group speed of the photons in the nuclear clouds is faster than the speed of light (this allows the theory of relativity, since no information is transmitted!) – the atoms had kept or absorbed the photons for a “negative period of time”.

And this is how it can be said that the next hundred years will remain exciting (unsurpassed).