Quantum Science: In-Depth Description

Image Credit: Scientific Frontline

Quantum Science is the multidisciplinary study and application of the physical properties of matter and energy at the scale of atoms and subatomic particles. Its primary goal is to understand the non-intuitive behaviors of the universe at its most fundamental level—characterized by probability, wave-particle duality, and non-locality—and to harness these phenomena to develop revolutionary technologies in computing, communication, and sensing.

Breakthrough could connect quantum computers at 200 times longer distance

New research from University of Chicago Pritzker School of Molecular Engineering Asst. Prof. Tian Zhong could make it possible for quantum computers to connect at distances up to 1,243 miles, shattering previous records.
Photo Credit: Jason Smith

A new nanofabrication approach could increase the range of quantum networks from a few kilometers to a potential 2,000 km, bringing quantum internet closer than ever

Quantum computers are powerful, lightning-fast and notoriously difficult to connect to one another over long distances. 

Previously, the maximum distance two quantum computers could connect through a fiber cable was a few kilometers. This means that, even if such cable were run between them, quantum computers in downtown Chicago’s Willis Tower and the University of Chicago Pritzker School of Molecular Engineering (UChicago PME) on the South Side would be too far apart to communicate with each other. 

A new approach links quantum physics and gravitation

Quantum-Geodesics 
Large masses – such as a galaxy – curve space-time. Objects move along a geodesic. If we take into account that space-time itself has quantum properties, deviations arise (dashed line vs. solid line).
Image Credit: © TU Wien  

A team at TU Wien combines quantum physics and general relativity theory – and discovers striking deviations from previous results. 

It is something like the “Holy Grail” of physics: unifying particle physics and gravitation. The world of tiny particles is described extremely well by quantum theory, while the world of gravitation is captured by Einstein’s general theory of relativity. But combining the two has not yet worked – the two leading theories of theoretical physics still do not quite fit together. 

There are many ideas for such a unification – with names like string theory, loop quantum gravity, canonical quantum gravity or asymptotically safe gravity. Each of them has its strengths and weaknesses. What has been missing so far, however, are observable predictions for measurable quantities and experimental data that could reveal which of these theories describes nature best. A new study from TU Wien may now have brought us a small step closer to this ambitious goal. 

When Quantum Gases Refuse to Follow the Rules

The team  Frederik Møller, Philipp Schüttelkopf and Jörg Schmiedmayer
Photo Credit: © Technische Universität Wien

At TU Wien, researchers have created a one-dimensional “quantum wire” made from a gas of ultracold atoms, where mass and energy flow without friction or loss. 

In physical systems, transport takes many forms, such as electric current through a wire, heat through metal, or even water through a pipe. Each of these flows can be described by how easily the underlying quantity—charge, energy, or mass—moves through a material. Normally, collisions and friction lead to resistance causing these flows to slow down or fade away. But in a new experiment at TU Wien, scientists have observed a system where that doesn’t happen at all. 

By confining thousands of rubidium atoms to move along a single line using magnetic and optical fields, they created an ultracold quantum gas in which energy and mass move with perfect efficiency. The results, now published in the journal Science, show that even after countless collisions, the flow remains stable and undiminished, thus revealing a kind of transport that defies the rules of ordinary matter. 

Light causes atomic layers to do the twist

Fang Liu, assistant professor of chemistry in Stanford’s School of Humanities and Sciences
Photo Credit: Fawn Hallenbeck/Stanford University

A study led by Stanford and Cornell researchers shows how light could be used to control the behavior of moiré materials, atomically thin layers that gain unusual properties when stacked and offset. The research has implications for developing superconductivity, magnetism, and quantum electronics.

A pulse of light sets the tempo in the material. Atoms in a crystalline sheet just a few atoms thick begin to move—not randomly, but in a coordinated rhythm, twisting and untwisting in sync like dancers following a beat.

Until now, researchers hadn’t been able to directly observe how those layers physically respond to a burst of light. In a recent study, a team led by Stanford and Cornell University researchers showed that the atomic layers can briefly twist more tightly together, then spring back, like a coiled ribbon releasing its energy.

Physicists discover new state of matter in electrons, platform to study quantum phenomena

From left, researchers Cyprian Lewandowski, Aman Kumar and Hitesh Changlani.
Photo Credit: Devin Bittner/FSU College of Arts and Sciences

Electricity powers our lives, including our cars, phones, computers and more, through the movement of electrons within a circuit. While we can’t see these electrons, electric currents moving through a conductor flow like water through a pipe to produce electricity.

Certain materials, however, allow that electron flow to “freeze” into crystallized shapes, triggering a transition in the state of matter that the electrons collectively form. This turns the material from a conductor to an insulator, stopping the flow of electrons and providing a unique window into their complex behavior. This phenomenon makes possible new technologies in quantum computing, advanced superconductivity for energy and medical imaging, lighting, and highly precise atomic clocks. 

A team of Florida State University-based physicists, including National High Magnetic Field Laboratory Dirac Postdoctoral Fellow Aman Kumar, Associate Professor Hitesh Changlani and Assistant Professor Cyprian Lewandowski, have shown the conditions necessary to stabilize a phase of matter in which electrons exist in a solid crystalline lattice but can “melt” into a liquid state, known as a generalized Wigner crystal. Their work was published in npj Quantum Materials, a Nature publication. 

The Quantum Door Mystery: Electrons That Can’t Find the Exit

Photo Credit: © Technische Universität Wien

What happens when electrons leave a solid material? This seemingly simple phenomenon has eluded accurate theoretical description until now. Researchers have found the missing piece of the puzzle.

Imagine a frog sitting inside a box. The box has a large opening at a certain height. Can the frog escape? That depends on how much energy it has: if it can jump high enough, it could in principle make it out. But whether it actually succeeds is another question. The height of the jump alone isn’t enough — the frog also needs to jump through the opening.

A similar situation arises with electrons inside a solid. When given a bit of extra energy — for example, by bombarding the material with additional electrons — they may be able to escape from the material. This effect has been known for many years and is widely used in technology. But surprisingly, it has never been possible to calculate this process accurately. A collaboration between several research groups at TU Wien has now solved this mystery: just like the frog, it’s not only the energy that matters — the electron also needs to find the right “exit,” a so-called “doorway state.”

New type of time crystals discovered

Time crystal 
Correlations between quantum particles result in a rhythmic signal – without the need for an external beat to set the tempo.
Image Credit: © TU Wien

Nature has many rhythms: the seasons result from the Earth's movement around the sun; the ticking of a pendulum clock results from the oscillation of its pendulum. These phenomena can be understood with very simple equations.

However, regular rhythms can also arise in a completely different way – by themselves, without an external clock, through the complex interaction of many particles. Instead of uniform disorder, a fixed rhythm emerges – this is referred to as a ‘time crystal’. Calculations by TU Wien (Vienna) now show that such time crystals can also be generated in a completely different way than previously thought. The quantum physical correlations between the particles, which were previously thought to be harmful for the emergence of such phenomena, can actually stabilize time crystals. This is a surprising new insight into the quantum physics of many-particle systems.

Measuring the quantum W state

Achieving the entanglement measurement of the W state
Image Credit: KyotoU / Takeuchi lab

The concept of quantum entanglement is emblematic of the gap between classical and quantum physics. Referring to a situation in which it is impossible to describe the physics of each photon separately, this key characteristic of quantum mechanics defies the classical expectation that each particle should have a reality of its own, which gravely concerned Einstein. Understanding the potential of this concept is essential for the realization of powerful new quantum technologies.

Developing such technologies will require the ability to freely generate a multi-photon quantum entangled state, and then to efficiently identify what kind of entangled state is present. However, when performing conventional quantum tomography, a method commonly used for state estimation, the number of measurements required grows exponentially with the number of photons, posing a significant data collection problem.

First distributed quantum algorithm brings quantum supercomputers closer

Dougal Main and Beth Nichol working on the distributed quantum computer.
Photo Credit: John Cairns.

In a milestone that brings quantum computing tangibly closer to large-scale practical use, scientists at Oxford University’s Department of Physics have demonstrated the first instance of distributed quantum computing. Using a photonic network interface, they successfully linked two separate quantum processors to form a single, fully connected quantum computer, paving the way to tackling computational challenges previously out of reach. The results have been published in Nature. 

The breakthrough addresses quantum’s ‘scalability problem’: a quantum computer powerful enough to be industry-disrupting would have to be capable of processing millions of qubits. Packing all these processors in a single device, however, would require a machine of an immense size. In this new approach, small quantum devices are linked together, enabling computations to be distributed across the network. In theory, there is no limit to the number of processors that could be in the network.  

Quantum mechanics helps with photosynthesis

First author Erika Keil and Prof. Jürgen Hauer in the lab.
Photo Credit: Andreas Heddergott / TUM

Photosynthesis - mainly carried out by plants - is based on a remarkably efficient energy conversion process. To generate chemical energy, sunlight must first be captured and transported further. This happens practically loss-free and extremely quickly. A new study by the Chair of Dynamic Spectroscopy at the Technical University of Munich (TUM) shows that quantum mechanical effects play a key role in this process. A team led by Erika Keil and Prof. Jürgen Hauer discovered this through measurements and simulations.

The efficient conversion of solar energy into storable forms of chemical energy is the dream of many engineers. Nature found a perfect solution to this problem billions of years ago. The new study shows that quantum mechanics is not just for physicists but also plays a key role in biology.

Photosynthetic organisms such as green plants use quantum mechanical processes to harness the energy of the sun, as Prof. Jürgen Hauer explains: “When light is absorbed in a leaf, for example, the electronic excitation energy is distributed over several states of each excited chlorophyll molecule; this is called a superposition of excited states. It is the first stage of an almost loss-free energy transfer within and between the molecules and makes the efficient onward transport of solar energy possible. Quantum mechanics is therefore central to understanding the first steps of energy transfer and charge separation.”

Even Quantum Physics Obeys the Law of Entropy

Image Credit: Courtesy of Technische Universität Wien

Is there a contradiction between quantum theory and thermodynamics? On the surface, yes - but at TU Wien, researchers have now shown how the two fit together perfectly.

It is one of the most important laws of nature that we know: The famous second law of thermodynamics says that the world gets more and more disordered when random chance is at play. Or, to put it more precisely: That entropy must increase in every closed system. Ordered structures lose their order, regular ice crystals turn into water, porcelain vases are broken up into shards. At first glance, however, quantum physics does not really seem to adhere to this rule: Mathematically speaking, entropy in quantum systems always remains the same.

A research team at TU Wien has now taken a closer look at this apparent contradiction and has been able to show: It depends on what kind of entropy you look at. If you define the concept of entropy in a way that it compatible with the basic ideas of quantum physics, then there is no longer any contradiction between quantum physics and thermodynamics. Entropy also increases in initially ordered quantum systems until it reaches a final state of disorder.

A new experimental system to bring quantum technologies closer to students

The expert Raúl Lahoz and a group of students with the new equipment for studying quantum physics.
 Photo Credit: Fundació Catalunya La Pedrera

The world of quantum physics is experiencing a second revolution, which will drive an exponential leap in the progress of computing, the internet, telecommunications, cybersecurity and biomedicine. Quantum technologies are attracting more and more students who want to learn about concepts from the subatomic world — such as quantum entanglement or quantum superposition — to explore the innovative potential of quantum science. In fact, understanding the non-intuitive nature of quantum technology concepts and recognizing their relevance to technological progress is one of the challenges of 2025, declared the International Year of Quantum Science and Technology by UNESCO.

Now, a team from the Faculty of Physics of the University of Barcelona has designed new experimental equipment that makes it possible for students to familiarize themselves with the more complex concepts of quantum physics. The configuration they present —versatile, cost-effective and with multiple ways of application in the classroom — is already operational in the Advanced Quantum Laboratory of the UB’s Faculty of Physics and could also be accessible in less specialized centers.

This innovation is presented in an article in the journal EPJ Quantum Technology, which results from a collaboration between professors Bruno Juliá, from the Department of Quantum Physics and Astrophysics and the UB Institute of Cosmos Sciences (ICCUB); Martí Duocastella, from the Department of Applied Physics and the UB Institute of Nanoscience and Nanotechnology (IN2UB), and José M. Gómez, from the Department of Electronic and Biomedical Engineering. It is based on the result of Raúl Lahoz’s master’s final project, with the participation of experts Lidia Lozano and Adrià Brú.

Engineering Quantum Entanglement at the Nanoscale

Study authors P. James Schuck (left) and Chiara Trovatello from the Schuck lab at Columbia Engineering.
Photo Credit: Jane Nisselson/Columbia Engineering

Physicists have spent more than a century measuring and making sense of the strange ways that photons, electrons, and other subatomic particles interact at extremely small scales. Engineers have spent decades figuring out how to take advantage of these phenomena to create new technologies.

In one such phenomenon, called quantum entanglement, pairs of photons become interconnected in such a way that the state of one photon instantly changes to match the state of its paired photon, no matter how far apart they are. 

Nearly 80 years ago, Albert Einstein referred to this phenomenon as "spooky action at a distance." Today, entanglement is the subject of research programs across the world — and it’s becoming a favored way to implement the most fundamental form of quantum information, the qubit. 

Quantum simulators: When nature reveals its natural laws

Photo Credit: © Oliver Diekmann/TU Wien

Quantum simulators are a completely new tool for research: quantum physics is studied by other kinds of quantum physics. Research teams from Innsbruck and Vienna are developing a new method that will allow this new technology to be reliably verified.

Quantum physics is a very diverse field: it describes particle collisions shortly after the Big Bang as well as electrons in solid materials or atoms far out in space. But not all quantum objects are equally easy to study. For some – such as the early universe – direct experiments are not possible at all. However, in many cases quantum simulators can be used instead: One quantum system (for example, a cloud of ultracold atoms) is studied in order to learn something about another system that looks physically very different, but still follows the same laws, i.e. adheres to the same mathematical equations.

It is often difficult to find out which equations determine a particular quantum system. Normally, one first has to make theoretical assumptions and then conduct experiments to check whether these assumptions prove correct. Strikingly, researchers at the University of Innsbruck, opens an external URL in a new window, the Institute of Quantum Optics and Quantum Information, opens an external URL in a new window (IQOQI) and TU Wien (Vienna) have now jointly achieved an important step in this field: they have developed a method that allows them to read directly from the experiment which physical theory effectively describes the behavior of the quantum system. This now allows for a new kind of quality control: it is possible to directly check whether the quantum simulator actually does what it is supposed to simulate. This should enable quantitative statements to be made about quantum systems that cannot be investigated directly.

Chemical reactions can scramble quantum information as well as black holes

Rice University theorist Peter Wolynes and collaborators at the University of Illinois Urbana-Champaign have shown that molecules can be as formidable at scrambling quantum information as black holes.
Image Credit: Courtesy of Martin Gruebele; DeepAI was used in image production

If you were to throw a message in a bottle into a black hole, all of the information in it, down to the quantum level, would become completely scrambled. Because in black holes this scrambling happens as quickly and thoroughly as quantum mechanics allows, they are generally considered nature’s ultimate information scramblers.

New research from Rice University theorist Peter Wolynes and collaborators at the University of Illinois Urbana-Champaign, however, shows that molecules can be as formidable at scrambling quantum information as black holes. Combining mathematical tools from black hole physics and chemical physics, they have shown that quantum information scrambling takes place in chemical reactions and can nearly reach the same quantum mechanical limit as it does in black holes. The work is published online in the Proceedings of the National Academy of Sciences.

“This study addresses a long-standing problem in chemical physics, which has to do with the question of how fast quantum information gets scrambled in molecules,” Wolynes said. “When people think about a reaction where two molecules come together, they think the atoms only perform a single motion where a bond is made or a bond is broken.

“It’s ultimately about predicting everything” – theory could be a map to hunted quantum materials

Photo Credit: Vendi Jukic Buca

A breakthrough in theoretical physics is an important step towards predicting the behavior of the fundamental matter of which our world is built. It can be used to calculate systems of enormous quantities of quantum particles, a feat thought impossible before. The University of Copenhagen research may prove of great importance for the design of quantum computers and could even be a map to superconductors that function at room-temperature.

On the fringes of theoretical physics, Berislav Buca investigates the nearly impossible by way of "exotic" mathematics. His latest theory is no exception. By making it possible to calculate the dynamics, i.e., movements and interactions, of systems with enormous quantities of quantum particles, it has delivered something that had been written off in physics. An impossibility made possible.

The unexpected presence of a white cat adorns the illustrations of Buca's research. Pulci the cat is his eye-catching muse. Arrows through the cat's body illustrate the quantum mechanical origin of the playful cat's movements – and this is precisely the relationship that Buca is trying to understand by making it possible to calculate the dynamics of the very smallest particles.

The breakthrough has reinvigorated an old and fundamental scientific question: Theoretically, if all behavior in the universe can be calculated by way of the laws of physics, can we then predict everything by calculating its smallest particles? 

Kapitza-Dirac effect used to show temporal evolution of electron waves

Time dependent interference fringes from the ultrafast Kapitza Dirac Effect. An electron wave packet is exposed to two counterpropagating ultrashort laser pulses. The time span from back to front is 10 pico seconds.
Illustration Credit: © Goethe University Frankfurt

One of the most fundamental interactions in physics is that of electrons and light. In an experiment at Goethe University Frankfurt, scientists have now managed to observe what is known as the Kapitza-Dirac effect for the first time in full temporal resolution. This effect was first postulated over 90 years ago, but only now are its finest details coming to light. 

It was one of the biggest surprises in the history of science: In the early days of quantum physics around 100 years ago, scholars discovered that the particles which make up our matter always behave like waves. Just as light can scatter at a double slit and produce scattering patterns, electrons can also display interference effects. In 1933, the two theorists Piotr Kapitza and Paul Dirac proved that an electron beam is even diffracted from a standing light wave (due to the particles' properties) and that interference effects as a result of the wave properties are to be expected. 

A German-Chinese team led by Professor Reinhard Dörner from Goethe University Frankfurt has succeeded in using this Kapitza-Dirac effect to visualize even the temporal evolution of the electron waves, known as the electrons' quantum mechanical phase. The researchers have now presented their results in the journal Science. 

Magnetic Avalanche Triggered by Quantum Effects

Christopher Simon holds a crystal of lithium holmium yttrium fluoride.
Photo Credit: Lance Hayashida/Caltech

Iron screws and other so-called ferromagnetic materials are made up of atoms with electrons that act like little magnets. Normally, the orientations of the magnets are aligned within one region of the material but are not aligned from one region to the next. Think of groups of tourists in Times Square pointing to different billboards all around them. But when a magnetic field is applied, the orientations of the magnets, or spins, in the different regions line up and the material becomes fully magnetized. This would be like the packs of tourists all turning to point at the same sign.

The process of spins lining up, however, does not happen all at once. Rather, when the magnetic field is applied, different regions, or so-called domains, influence others nearby, and the changes spread across the material in a clumpy fashion. Scientists often compare this effect to an avalanche of snow, where one small lump of snow starts falling, pushing on other nearby lumps, until the entire mountainside of snow is tumbling down in the same direction.

A new type of cooling for quantum simulators

Tiantian Zhang and Maximilian Prüfer discussing measurements in the quantum lab
Photo Credit: Courtesy of Technische Universität Wien

Quantum experiments always have to deal with the same problem, regardless of whether they involve quantum computers, quantum teleportation or new types of quantum sensors: quantum effects break down very easily. They are extremely sensitive to external disturbances - for example, to fluctuations caused simply by the surrounding temperature. It is therefore important to be able to cool down quantum experiments as effectively as possible.

At TU Wien (Vienna), it has now been shown that this type of cooling can be achieved in an interesting new way: A Bose-Einstein condensate is split into two parts, neither abruptly nor particularly slowly, but with a very specific temporal dynamic that ensures that random fluctuations are prevented as perfectly as possible. In this way, the relevant temperature in the already extremely cold Bose-Einstein condensate can be significantly reduced. This is important for quantum simulators, which are used at TU Wien to gain insights into quantum effects that could not be investigated using previous methods.