UNIVERSITY PARK, Pa. — This year, the world is marking the 100th anniversary of quantum mechanics, the beginning of a scientific revolution so important that it prompted the United Nations to declare 2025 as the International Year of Quantum Science and Technology.

Quantum science — the study of the behavior of subatomic particles — has already changed our world, guiding scientists and engineers in everything from developing new semiconductors, which are a staple of electronic devices, to designing the latest lasers that can be used in a range of applications, from precision surgery to industrial etching.

But, according to experts, this is just the beginning. Some optimistic experts suggest that in the next few years, quantum science could deliver the next industrial revolution with inventions and services that are truly mind-boggling, including computers that can tackle problems that our normal classical devices would take millennia to solve, and communication techniques that will deliver messages over super-secure networks. But these same experts also warn that quantum technologies could hack today’s cybersecurity measures.

Penn State Eberly College of Science faculty and Eberly-trained researchers have played a pioneering role in the exploration and development of quantum science and are currently working to nurture this “second quantum revolution,” deepening understanding of the world and applying that knowledge to improve everyday life.

What is quantum mechanics?

Often labeled “spooky” and weird by practitioners and detractors alike, quantum theory is one of the most rigorously tested and experimentally verified frameworks in the history of science. Its predictions have been confirmed with extraordinary precision across a wide range of phenomena, making it a cornerstone of today’s — and likely tomorrow’s — physics.

But what is it, exactly?

Essentially, scientists use quantum mechanics to explore the behavior of matter and energy at the smallest scales, such as atoms and subatomic particles. Unlike classical physics, which describes the world in terms of a set of fixed laws, quantum mechanics operates on probabilities. This is because these particles’ behavior often defies intuition. For example, quantum mechanics relies on concepts such as superposition and entanglement. Superposition is the ability of a quantum system to exist in multiple probabilistic states simultaneously until it is measured. For example, an electron in an atom doesn't occupy a single fixed position but exists as a "cloud" of probabilities and so offers a range of possible positions and energies at once. When a measurement occurs, this cloud "collapses" to a definite state.

Entanglement is another cornerstone of quantum mechanics that reveals the interconnectedness of particles. When two or more particles originate in close proximity, they can become entangled, meaning their states are correlated regardless of the distance between them. Measuring the state of one particle instantly determines the state of its entangled partner, a phenomenon Albert Einstein famously referred to as "spooky action at a distance."

Together, superposition and entanglement are fundamental to quantum science, making it both scientifically and philosophically interesting — and opening up the potential for commercially important quantum technologies.

Connecting molecular systems to quantum information science

Eberly College of Science researchers are finding that these seemingly otherworldly properties of quantum mechanics can inspire some down-to-earth benefits. For example, quantum science is a win-win for chemistry: Not only can quantum science lead to deeper understanding of chemistry, but scientists are also discovering ways to use chemistry to improve quantum devices, like sensors and quantum computers.

Quantum devices rely on an electron’s ability to retain quantum information over time, which depends on how it is spinning. But a variety of factors can interfere with this “spin coherence.” Kenneth Knappenberger Jr., department head and professor of chemistry, and his team are just one of the groups in the college that are combining quantum and chemistry to address the critical challenge of maintaining spin coherence in molecular systems.

“The big challenge is that after you initialize spin coherence, it rapidly decays,” Knappenberger said. “It doesn't stick around long enough to do anything with it. And, so, this is where we come in, because the root cause of this problem is really a chemistry problem.”

Maintaining spin coherence in molecular systems is a little like keeping a group of perfectly synchronized dancers moving in unison on a stage while surrounded by random gusts of wind that can throw off their timing. Just as the dancers need precise control and coordination to resist external interference, molecular spin coherence requires isolating the system from environmental noise to preserve its quantum state.

Increasing a system’s ability to maintain quantum information could lead to, as a few examples, better imaging technology and ways to make computers faster and more efficient, according to Knappenberger.

"We do a lot of research that is basically dedicated to understanding how to maintain electronic spin-coherence lifetimes, which is the persistence of spin,” Knappenberger said, adding that it could help computing because “controlling and moving spin around” is required for something like logic gates, which are fundamental to digital circuits.

Knappenberger's research group is particularly interested in understanding how molecular vibrations — the natural oscillation of atoms within a molecule — disrupt spin states. For example, Nate Smith, a graduate researcher in the Knappenberger group, is investigating how precise atomic- and molecular-level control can influence electron spin behavior in metal nanostructures. By combining the creation of advanced nanomaterials with a state-of-the-art technique that uses lasers to image materials under magnetic fields, they can study how the spin of a material’s electrons “couples” or interacts with the vibrations.

“One practical thing that you can do is actually suppress those vibrations,” Knappenberger explained. “We’ve been using solvents and ligands that make the system more rigid so that the electron retains its memory. This is analogous to shielding the synchronized dancers from the wind that disrupts their precision; molecular vibrations are like the wind in this analogy. Achieving a fundamental understanding of why electron spin and vibration couple could lead to breakthroughs, allowing us to design materials where we control vibrations to give the desired effects.”

This research could have important ramifications for everyday use, Knappenberger said.  For example, extending the lifetime of specific spin states and enabling controlled transitions between them could potentially lead to energy-efficient spintronic devices used in digital storage and boost the robustness of quantum computers.

While physics today is most associated with quantum information science, Knappenberger emphasized the critical role of chemistry in addressing quantum challenges.

“Physicists conceptualize quantum systems, but chemists can play an important role by providing the material solutions needed to embed those ideas into reality,” he said. “Chemists can contribute by synthesizing and designing materials that function outside of a vacuum. … The challenges of practical quantum information sciences present problems we realize we don’t fundamentally understand at the molecular level. That then becomes a research problem for us.”

Penn State is an ideal place to study and answer these questions, according to Knappenberger.

"We are very fortunate to be surrounded by some of the world’s leading experts in the synthesis and characterization of atomically precise materials, theoretical descriptions of electronic and vibrational dynamics, and the measurement of a material’s electronic spin properties," Knappenberger said. "This powerful make-model-measure approach sets Penn State apart from many other universities in the quantum information sciences arena."

Quantum topology and quantum computing

Traditional quantum computers, which rely on the fragile quantum equivalent of computer bits, called qubits, face major challenges due to errors caused by environmental noise and temperature sensitivity. These issues make them impractical for everyday use, as they often require extremely cold environments to function, typically below -270 degrees Celsius, approaching absolute zero. One promising alternative lies in using topological insulators, materials with unique properties where electrical conduction happens along their edges without resistance due to special quantum effects. Researchers like Cui-Zu Chang, professor of physics, are exploring the potential of these materials for future quantum devices.

"There are two main types of quantum computing — the traditional kind, based on approaches like superconductors, and the topological approach that we're working on," he said. "Topological quantum computing has the potential to be more powerful and robust.”

Topological quantum computing leverages the unique properties of certain quantum systems, where quantum information is encoded in the overall layout — or global topology — of the system rather than its local states. You could think of this as a carpet, where you could pull a few threads but the overall pattern remains. In quantum computing, although those threads — or local states — are prone to errors that can accumulate over time, these errors do not impact the carpet, or global topology, making the topological approach far more stable than traditional quantum computers.

One of the keys to developing topological systems is harnessing the unique properties of topological insulators, materials that behave as insulators internally but allow electrons to flow freely on their surface. Chang's team is specifically focused on the quantum anomalous Hall (QAH) effect, a phenomenon where the material conducts electricity only along its edges, with no resistance, thanks to the special quantum properties of electrons in topological insulators.

"We employ a technique called molecular beam epitaxy to grow magnetically doped topological insulator thin films and heterostructures for the realization of this topological quantum phenomena," said Chang, who, in 2013, became the first person to synthesize real materials that demonstrate the QAH effect. "Because the quantum anomalous Hall effect that we are studying is a topological phenomenon, we could — based on that — build a topological quantum computer."

Unlike traditional quantum computers, which are fragile and susceptible to environmental interference, topological quantum devices could be inherently fault tolerant, a requirement for practical applications, Chang added.

Harnessing these quantum effects at practical temperatures, however, remains a challenge.

"The materials for realizing the QAH effect are really sensitive," Chang said. "When you take it out of the ultrahigh-vacuum environment we grow it in, the material can degrade. If we want to apply these materials in quantum technology, we need to be able to use them in normal air pressure and at normal temperatures, not just in the labs."

By addressing the sensitivity and temperature limitations of quantum materials, Chang said his team hopes to leverage quantum phenomena to develop practical applications based on the QAH insulators, including their use in topological quantum computing.

"If we aim to harness this quantum phenomenon for practical applications, it must be realized at higher temperatures. This is one of the key directions we are pursuing," Chang explained.

Exploring the cosmos with quantum

When we typically think of quantum, we picture the very small: tiny qubits and chemical and molecular reactions. But Eberly scientists are also using quantum mechanics to better understand big things — like the entire universe.

Sarah Shandera, professor of physics, is one of those researchers. She noted that the origin story of the universe is deeply rooted in quantum phenomena, with quantum fluctuations and properties serving as the foundation for the structure we observe today.

But studying the early universe is difficult. The most powerful telescopes can detect light from events that occurred billions of years ago, but there’s a limit. There are boundaries to our ability to see the past. Shandera uses concepts from an idea called open systems, which suggests that when there are boundaries or horizons that restrict an observer's view, complex modeling is required to account for the flow of information, energy, and correlations across those boundaries.

Shandera has taken on the challenge of defining and modeling these boundaries, attempting to understand the nature of open quantum systems together with horizons imposed by gravity.

“This is, in general, the origin story of the universe, or what we know about the very earliest moments in the universe's history,” said Shandera, who is also the director of the Penn State Institute for Gravitation and the Cosmos. “The quantum physics that was happening at that time was key. Somehow these quantum properties and the quantum fluctuations and the quantum structure of particles and matter were the seed for how the rest of the universe — which we have thus far understood at the level of classical and Einsteinian physics — was derived."

According to Shandera, quantum mechanics — and maybe even, one day, quantum computers — will guide her investigations into big questions about gravity and open systems.

This open-systems perspective is crucial for modeling complex quantum systems, like those at play at the beginning of the universe, and it may also improve quantum computers by helping to deal with the inherent noise. And eventually, Shandera said, quantum computers may in turn guide her investigations into big questions about gravity and open systems.

Quantum cryptography

The superpowers of quantum technologies are considerable — from better modeling chemical reactions to getting a glimpse into the origin of the universe.

However, to paraphrase Spider-Man’s Uncle Ben and possibly Voltaire, depending on who you ask: with these great powers comes great responsibility. Because with all quantum computing’s transformative powers for good, their amazing number-crunching ability poses significant risks to the encryption methods that keep our data safe.

But Eberly scientists are on top of that, too, by creating ways to encrypt data that quantum computers can’t hack.

Professor of Mathematics and Pentz Professor of Science Kirsten Eisenträger's research focuses on developing secure cryptographic systems that can withstand the threat of quantum computers and analyze the security of recently proposed systems.

According to Eisenträger, current public key encryption methods like the RSA cryptosystem and elliptic curve cryptography are vulnerable to being broken by quantum algorithms. She also investigates alternatives, particularly protocols based on isogenies, or specialized mathematical mapping, and lattice-based protocols. Lattice-based protocols are cryptographic systems that rely on complex geometric structures called lattices, which could be considered mazes so complex that even quantum computers can’t find a way out — or in.

While there are several promising alternatives to protect against quantum attacks, such as lattice-based approaches, Eisenträger said she wants as many options as possible on the table to keep up with the fast-evolving cryptographic hackers who could inflict trillions — with a t — of dollars of damage on the economy.

“I'm a proponent of not limiting our options and not basing all the new systems on just one method,” Eisenträger said. “There should still be a variety of systems, and people should not just work on better functionality for the systems but also still spend time checking to see whether they are really secure.”

Eisenträger’s interdisciplinary collaborations with computer scientists at Penn State have been crucial to understanding the quantum computing threat and developing robust solutions. She emphasized the challenges of bridging different fields but believes this cross-pollination of expertise is essential for addressing the complex problems in post-quantum cryptography.

"I feel like it's so timely and so exciting, and so I've collaborated with Sean Hallgren from computer science at Penn State, who's an expert in quantum algorithms,” she said. “Together, we have a unique expertise — we have the quantum side, the computer science side and then the math, working on the underlying hard problems."

Building on core strengths

Together, the broad array of quantum research at Penn State will accelerate scientists’ ability to harness the special properties of quantum materials in ways that could ultimately improve computing, medicine, cybersecurity and our understanding of the universe.

“Penn State has a long history of foundational research in both the theory and application of physics, materials science, computing and engineering,” said Andrew Read, senior vice president for research at Penn State. “We are well positioned to translate cutting-edge research into real-world solutions as well as meet both the challenges and the opportunities of quantum science. Additionally, through our strong commitment to training and education, we are cultivating the next generation of quantum scientists, engineers and entrepreneurs, helping them develop skills required in the rapidly evolving quantum landscape.”

According to Mauricio Terrones, George A. and Margaret M. Downsbrough Head of the Department of Physics, Evan Pugh University Professor, and professor of chemistry and of materials science and engineering, there are bright spots across the college, but he highlighted several key strengths of Penn State's quantum research.

“The University’s expertise and leadership in materials science is critical for quantum applications,” he said.” For example, the Two-Dimensional Crystal Consortium (2DCC) focuses on materials like crystals and films, which experience unique quantum phenomena because their electrons are confined to two dimensions. Additionally, Penn State’s state-of-the-art facilities in nanofabrication and characterization allow our researchers to develop and study sensitive materials and devices with unique properties.”

Terrones also noted that leading theorists and experimentalists are working on the fundamentals of quantum computing in the department

 “For example, the Atomic, Molecular, and Optical (AMO) Physics group uses theoretical tools and exquisite experimental control over atoms and photons to understand unique material properties, including topological principles, that may ultimately support the development of quantum bits and other quantum applications,” Terrones said.

Building complex quantum technologies requires contributions from across fields and disciplines, Terrones said, adding that Penn State has a strong tradition of multidisciplinary research and workforce development that can create the scientists who work on these complex quantum projects.

"Nature doesn’t work the way universities do,” Terrones said. “While university systems generally tend to be compartmentalized, we don’t believe that compartmentalization and science mix. Penn State’s specialized framework of our centers and institutes uniquely facilitates collaboration and provide our students with a broad foundation that will serve them well in a wide variety of potential careers in quantum. We take the responsibility to develop tomorrow’s workforce and train the new generation of researchers very seriously.”

Editor's note: This story first appeared in the spring 2025 issue of the Science Journal, the Eberly College of Science magazine.