Quantum communication and computing are at the forefront of technological innovation, offering faster and more secure data processing compared to traditional methods.
At the core of these advancements are qubits, the fundamental units of information in quantum systems, much like bits in conventional computing.
Unlike classical systems that use electrical pulses or laser beams to transmit data, quantum communication leverages individual photons. This makes the transmission of data virtually impossible to intercept, paving the way for ultra-secure communication channels.
Qubits that can be controlled or read using light are essential in this realm, as they are able to absorb, process, and emit quantum information via photons.
However, developing stable qubits that can store data long enough to be useful in real-world applications remains a key challenge in the quest to build scalable quantum computers.
Enhancing qubit stability
A major obstacle in quantum computing is increasing the coherence time—the period during which a qubit can maintain stable quantum states.
The longer this time, the more effective the qubits are at storing and processing information. Extending this coherence time is essential for making quantum computing viable on a larger scale.
At Karlsruhe Institute of Technology (KIT), doctoral researchers Ioannis Karapatzakis and Jeremias Resch have made significant progress in this area by studying defects in diamonds, specifically tin-vacancy (SnV) centers.
These defects occur when carbon atoms in the diamond lattice are replaced by tin atoms, resulting in unique optical and magnetic properties.
Their research is part of Germany’s federally funded initiatives QuantumRepeater.Link (QR.X), aimed at advancing secure quantum communication, and SPINNING, a project focused on developing quantum computers based on diamond spin-photon technology.
Quantum communication with diamond defects
The defects in diamonds, like SnV centers, have special properties that make them ideal qubits for quantum communication.
These centers allow the electron spin—a quantum state that can store information—to be manipulated using light or microwaves. The information can then be transmitted by coupling the qubits to photons, creating a secure quantum communication channel.
The team was able to control these defects and improve their stability, making them a promising component for future quantum communication systems.
Karapatzakis and Resch made a major breakthrough by extending the coherence time of these diamond qubits to 10 milliseconds, a substantial improvement over previous results.
This was achieved through a technique called dynamical decoupling, which minimises interference and enhances qubit stability. Moreover, they demonstrated for the first time that SnV centers in diamonds can be controlled efficiently using superconducting waveguides.
These waveguides direct microwave radiation to the defects while avoiding heat generation, which is crucial for maintaining qubit performance at extremely low temperatures.
The future of quantum communication
The ability to transfer quantum states from qubits to photons is essential for establishing quantum communication between users or even quantum computers.
By successfully controlling tin-vacancy centers and demonstrating stable spectral properties, the KIT researchers have taken a major step toward realising secure and efficient quantum communication systems.
Their findings not only push the boundaries of current technology but also set the stage for future breakthroughs in quantum networks and computing.
The advancements in controlling diamond-based qubits could play a pivotal role in the development of quantum communication, bringing this revolutionary technology closer to real-world applications.
