25/11/2025
Prof. Dr. Emre Erdem
Sabancı University - Faculty of Engineering and Natural Sciences
One of the most important steps that opened the door to the quantum world was taken nearly a century ago. Werner Heisenberg's work, published in 1925, is considered the paper that laid the mathematical foundation for modern quantum mechanics. Just a few years before this paper, the Stern–Gerlach experiment, conducted in 1922, effectively opened the door to this new world. In the experiment, a beam of silver atoms was passed through a strong magnetic field. Only a slight deflection was expected; however, the beam split in two. This surprising result revealed the existence of tiny, invisible "magnets" within atoms. This was the first time that the quantum property of electrons, called "spin," had been revealed so clearly. For Niels Bohr and the physicists of the time, this was a historic gateway to a counterintuitive yet remarkably consistent aspect of nature.
While spin may sound like a spinning motion, it's actually an intrinsic property of the electron. It forces the electron to behave like a tiny magnet. Furthermore, this spin isn't just "up" or "down"; it can also exist in a mixture of both states simultaneously. This is called superposition. This property explains why the qubit, the fundamental building block of quantum computers, is so powerful: A qubit can be both 0 and 1 simultaneously.
One of the most interesting developments in this field is the ability to create qubits by exploiting defects within diamond crystals. A small gap sometimes forms between the carbon atoms of a diamond, and a nitrogen atom can be found right next to this gap. This structure is called an NV center. Simply put, an NV center is a "hole + nitrogen pair." The spins of the electrons trapped within this center can be controlled with light or a magnetic field. These spins can even be read by emitting colored light. A measure of a diamond's suitability for quantum technologies is how well these centers are organized and stable. Thus, diamond ceases to be a material used only in jewelry and becomes a quantum material that can become the heart of quantum computers of the future.
To control spins, one must first "see" them. The Electron Spin Resonance (ESR) device used at Sabancı University's EFSUN laboratories is a technology that can do exactly this. ESR measures the behavior of electron spins in materials under magnetic fields. This method allows us to determine an electron's spin state, how it interacts with its environment, and what defects it contains. This allows us to determine whether a material is suitable for quantum technologies at an early stage. This is a significant advantage for both research and the design of future quantum devices.
These studies aren't just being conducted for scientific curiosity. Spins and spin-based qubits have the potential to directly shape future technologies. As quantum computers develop, they will impact many areas, including the design of new drug molecules, more accurate calculations of climate models, simulation of complex robot behavior, and the acceleration of materials development processes. We're talking about an era in which some calculations that classical computers can't solve in days will be completed in seconds.
However, we must be realistic: These technologies won't be readily integrated into our daily lives in the near future. There are several reasons for this. First, qubits are extremely sensitive to even the slightest environmental influences; they can easily be damaged. Therefore, most systems require very low temperatures to function. Second, spins are very difficult to control both stably and accurately. Third, creating systems that can operate hundreds or thousands of qubits simultaneously remains a major engineering challenge. So, while the power promised by quantum computers is real, making them reliable and accessible to everyone will take time.
That's why it's significant that 2025 is called the "Year of Quantum." On the one hand, we are witnessing the culmination of 100 years of accumulated knowledge in fundamental science; on the other, we are in a period where quantum technologies are no longer confined to the laboratory and are beginning to transform into real-world devices. Spin-based qubit systems are considered one of the strongest candidates in this race. This is because spins have properties that already exist in nature, are stable, controllable, and compatible with the techniques used in chip manufacturing today.
In short, the tiny "spin" property of an electron, discovered nearly a century ago, is now laying the foundation for a new era of information processing for humanity. Perhaps the computers, sensors, and communication technologies of the future—and even many innovations we haven't yet imagined—will be based on the precise control of this tiny quantum property. As we continue to better understand these spins in our laboratories, we will continue to contribute to the shaping of the quantum age.
