Quantum technology is one of the most exciting areas of research today, with the potential to make huge leaps forward in areas such as communications, metrology and computing. But what are the technical foundations of quantum computers or quantum sensors? And how does the theory of quantum physics translate into practical applications?
What is quantum technology?
Quantum technology is a very theoretical branch of physics (quantum physics) based on quantum mechanics. This is a physical theory in which researchers try to describe the properties and laws of states and processes of matter. The special thing about it is that these calculations take place at the scale of atoms or even smaller. Quantum mechanics is therefore also the basis for describing phenomena in atomic physics.
Quantum mechanics is fundamentally concerned with material objects. The question is how these objects move under the influence of forces, and whether it is possible to calculate possible future states as a result. These calculations quickly lead to principles that contradict conventional physical principles. For this reason, it is considered to be particularly complex and difficult to understand. However, today’s applications of quantum technology can also be found in purely digital areas, such as cryptography.
How it all began
The beginnings of quantum mechanics can be found between 1925 and 1932 with the discoveries of Werner Heisenberg, Erwin Schrödinger, Max Born and others. They built on an ‘older quantum physics’ that Albert Einstein, Max Planck and Niels Bohr had already worked on. At that time, everything revolved around the question of how to describe the state of atoms.
Particular milestones were:
- Wave mechanics (Louis de Broglie)
- Matrix mechanics (Werner Heisenberg, Max Born, Pascual Jordan)
- Schrödinger equation (Erwin Schrödinger)
- Uncertainty Principle (Werner Heisenberg)
Although most people would not be able to explain these physical principles, or would only be able to do so vaguely, their names or common expressions such as ‘Schrödinger’s cat’ are familiar even to the layman. Quantum physics ushered in a new golden age of physics research, which continues to this day. New areas of research have emerged, such as quantum field theory and quantum electrodynamics.
Quantum mechanics – how does it work?
It would probably take a whole book to explain quantum mechanics in detail.
So here are just the main points:
- Quantum objects, wave function and wave-particle duality: The wave function is used to calculate how a particle behaves. In principle, particle behaviour and wave behaviour can be considered independently of each other.
- Superposition: It is possible for a quantum object to exist in several states at the same time, which is known as superposition.
- Entanglement: Two or more objects can be connected in such a way that they influence each other, even over long distances.
- Quantum Jumps and Uncertainty Principle: When an electron in an atom jumps from one state to another without any intermediate states, this is called a quantum jump.
- Heisenberg’s uncertainty principle: The more precisely we try to measure the position of a particle, the more fuzzy it becomes. This is why there are only probabilities for calculations, not certainties.
Quantum technology in practice – the example of quantum sensors
But how do you turn this basic research into new products that can be used in industry? After all, a technology is only really established when the theoretical basic research can be translated into practical applications and products – and offers clear advantages over other established technologies. Let us consider this question using quantum sensing as an example: What do the principles of quantum physics described above mean for use in sensing? What advantages do quantum sensors have over conventional measuring devices and what does this mean for use in industry and research?
Wave function
The wave function is central because it is the basis for describing and predicting quantum phenomena. In quantum sensing, it is important to control and manipulate the wave function of a system in order to make precise measurements. The probability amplitudes within the wave function provide information about how likely it is to find a particle at a particular location or in a particular state. This information is crucial for calibrating the sensitivity of quantum sensors and determining the optimal measurement conditions.
Superposition
A quantum system in a superposition state can be very sensitive to external influences such as magnetic fields, electric fields or temperature changes. By precisely controlling and measuring the superposition, these external influences can be very precisely determined. One example is the use of nitrogen vacancy centres in diamonds as highly sensitive magnetic field sensors.
This allows highly sensitive measurements to be made that would not be possible with conventional sensors. For example, quantum magnetometers can measure extremely weak magnetic fields, such as those generated by electrical activity in the brain or heart, enabling more accurate and non-invasive diagnoses using magnetoencephalography (MEG) or magnetocardiography (MCG).
Entanglement
Entanglement is another key mechanism in quantum sensing. In entanglement, the state of one particle remains correlated with that of the other, even when they are far apart. This property is used to make measurements that are extremely sensitive. Entangled states increase the precision and sensitivity of sensors because they can reduce quantum noise, making measurements more accurate.
This is particularly useful in low-quantum-noise interferometers, which are used, for example, in gravimetry to measure the Earth’s gravitational field. There, quantum-based instruments can detect the tiniest changes, which can help in the search for oil, gas or mineral deposits, or in monitoring volcanoes and making more accurate predictions.
Uncertainty Principle
Heisenberg’s Uncertainty Principle imposes a limit on the accuracy with which certain measurements can be made simultaneously. Quantum sensing seeks to understand these limits and optimise measurement results by developing measurement strategies that minimise quantum noise and maximise precision. In this sense, the uncertainty principle provides a limit that researchers can work towards, inspiring them to constantly develop new innovations for even more precise measurements.
Industrially viable products
As you can see, there are many reasons to believe that quantum-based measurement devices offer unique advantages. But are there also products that can be used in industry today? The answer is yes! The first market-ready products that combine the benefits of quantum sensing with products suitable for industrial use are appearing on the market. A good example is the Quantum Magnetometer from Quantum Technologies. This ultra-fine sensor not only provides measurements in the nanometre range, it is also compact and robust enough to be used in complex environments such as electric vehicles, solar and wind power plants, and smart factories.Quantum technology in use today
We can already see examples of how quantum technology is improving our research, development and production, and not just in the field of sensors.
Scanning tunnelling microscopy (tunnel effect)
Scanning tunnelling microscopy is used to study the surface structure of materials at the atomic level. It exploits the tunnelling effect, a central phenomenon of quantum mechanics. The tunnelling effect occurs as follows: when an extremely sharp metal tip (the ‘scanning cone’) is brought very close to a conductive surface (less than 1 nanometre away), electrons can ‘tunnel’ through the tiny gap, even if the direct transition would be blocked by an energy barrier. This tunneling effect produces a measurable electric current, called the tunneling current. The tunnelling current depends strongly on the distance between the tip and the surface. Changing the distance by just a few picometres (trillionths of a metre) leads to a significant change in the tunneling current. This makes it possible to map the atomic structure of the surface with high precision.
Scanning tunnelling microscopy can therefore be used to examine semiconductors, metals or nanomaterials for the tiniest irregularities, opening up new possibilities for microelectronics.
Flash memory (tunneling effect)
Flash memory is a type of non-volatile memory used in many devices such as USB sticks, SSDs and memory cards. The tunnelling effect plays a crucial role in storing and erasing data. A memory is made up of millions of transistors that contain an isolated layer (the ‘floating gate’). Electrons can be stored on this floating gate. To store data, a high voltage is applied, causing electrons to ‘tunnel’ through a thin insulating layer (oxide) to the floating gate. The electrons remain stored there, trapped by the oxide layer, even when the voltage is switched off. When the data is erased, the voltage is reversed. This causes the electrons to tunnel back through the oxide layer and the floating gate is discharged.Flash memory is particularly durable and reliable because the insulating effect of the floating gate protects the stored electrons over a long period of time. They also consume little power because no energy is required to maintain the data after storage. Because flash memory offers a lot of storage capacity in a small space, it is also very compact, making it suitable for small devices such as smartphones, in smart cars or other IoT devices.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is already widely used in medicine. It provides detailed images of the inside of the body using physical principles such as strong magnetic fields and radio frequency waves. Background: Many atoms in the body, in particular the hydrogen nuclei (protons) in water molecules, have a property called spin, a type of quantum mechanical angular momentum. A strong magnet in the MRI machine orients the hydrogen nuclei (protons) in the body, which behave like small magnets. A short pulse knocks the protons out of alignment and tilts them into a superposition. They start to move and emit weak radio signals. The protons then return to their original position. As they do so, they emit energy that is measured by sensors. Because different types of tissue produce different signals, a contrast is created that is detected by the machine and combined into an image.
Not only can MRI imaging show the individual layers of tissue very accurately, but unlike X-rays and CT scanners, it does not use radiation.
Bose-Einstein Condensate (MAIUS 1 spacecraft)
A Bose-Einstein condensate (BEC) is a special state of matter formed when atoms are cooled to extremely low temperatures close to absolute zero. In this state, the atoms ‘merge’ and behave like a single large particle that behaves quantum mechanically. For example, all the atoms oscillate synchronously and exhibit collective behaviour. In addition, a BEC can move without friction (superfluidity) and is particularly sensitive to the smallest external influences such as forces and fields. This makes them particularly interesting for precision measurements and experiments in quantum physics.
The MAIUS1 spacecraft was launched in 2017. Scientists succeeded in creating a Bose-Einstein condensate in space and using it for interferometry experiments. This discovery is crucial for use in space travel and future scientific experiments. The success of the mission has paved the way for new experiments with BECs in space and could enable long-term applications in navigation, geodesy and fundamental physics research. The MAIUS2 spacecraft was launched in December 2023 with the mission of creating a Bose-Einstein condensate from two different atomic species (rubidium and potassium).
Quantum Cryptography & Quantum Computing
Quantum cryptography uses the laws of quantum mechanics to encrypt information with absolute security. An encrypted key is transmitted via quantum states. Because of quantum mechanics, information cannot be intercepted (tapped) without altering the data, which is immediately detectable. Quantum cryptography is seen as a new milestone in protecting against fraud and cyber-attacks, particularly in business sectors and industries that manage sensitive data, such as finance, insurance and healthcare.
Quantum computing has also made headlines in recent months with new developments and products, especially when it comes to quantum computers. These no longer work with bits, but with qubits. Qubits can not only be 0 or 1, but can also be both at the same time by superposition. Advantages: Quantum computers use quantum entanglement and parallel processing. This allows them to solve certain problems, for example in cryptography or materials research, much faster than conventional computers. Companies such as IBM and Google are leading the way with their quantum computers. Google, for example, unveiled a new quantum chip in December. This chip would far exceed the computing speed of any computer currently available. The new Google chip takes less than five minutes to perform a benchmark calculation that would take the fastest supercomputers available today about ten septillion years (a period of time that would exceed the age of the universe). At present, however, quantum computers are still slightly prone to error. This is mainly due to the sensitivity of the qubits and the physical limitations of today’s hardware. Only when companies have developed more stable qubit technologies and can reliably avoid or correct errors will quantum computers be ready to be scaled up for widespread use.
Quantum teleportation
Quantum teleportation is a quantum mechanical process in which the state of a particle (e.g. a photon or an atom) is transferred from one location to another without the particle itself travelling through space. It is therefore not a case of ‘beaming’ an object, but rather the precise transfer of information about the state of a particle.
Quantum teleportation thus enables the secure exchange of quantum states, which is essential for future quantum networks. In a quantum internet, information can be transmitted in an entangled and tap-proof manner. In addition, entangled states can be transported over long distances. Quantum teleportation also plays an important role in quantum computing: it helps to transfer qubits between different parts of a quantum computer without destroying their sensitive states.
Superconductors (needed for fusion power plants, for example)
Superconductors are materials that completely lose their electrical resistance above a certain temperature (transition temperature). This means that they can conduct electricity without any loss of energy. Superconductivity occurs when the electrons in the material form so-called Cooper pairs, which move through the lattice of the material without resistance. Research is currently underway to develop room-temperature superconductors so that the technology can be used for other purposes.
In fusion power plants, superconductors play a crucial role in generating and controlling the extremely strong magnetic fields required for fusion. For example, hot plasma (temperatures of over 100 million degrees) is generated in fusion reactors where the fusion of hydrogen isotopes (e.g. deuterium and tritium) takes place. The plasma is so hot that it cannot come into contact with the walls. It is therefore confined and kept in suspension by strong magnetic fields. These magnetic fields are generated by superconducting coils because they require very high currents, which would cause enormous energy losses with normal conductors.
Another important point is energy efficiency: superconductors make it possible to generate the magnetic fields without heat loss, which significantly increases the energy efficiency of the fusion power plant. Without superconductors, energy losses would be so high that a fusion power plant would not be economically viable.
Theory becomes reality
What began about 100 years ago with the question of how to describe the state of atoms heralded a paradigm shift in physics and changed the way we understand and describe our world. Today, quantum technology is a thriving discipline in physics research. It is now up to thought leaders to put the achievements in this field into practice and drive them forward.
Images: Adobe Stock
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