Quantum computers and quantum communication are groundbreaking technologies that enable faster and more secure data processing and transmission compared to traditional computers. In quantum computers, qubits serve as the fundamental units of information, functioning as the quantum mechanical equivalent of bits in classical computing.
Where, for example, laser pulses in a glass fiber transport information from A to B in classical digital communication, quantum mechanics uses individual photons. In principle, this makes it impossible to intercept the transmitted data. Qubits that are optically addressable (can be controlled or read out with light) are suitable for storing the photons’ information and processing it in quantum computers. The qubits can store and process quantum states, and absorb and emit them in the form of photons.
Qubit Stability Is Key
A major challenge in qubit development is extending the coherence time, i.e. the time in which qubits can store information in a stable manner. Being able to control qubits and keep them stable enough to exploit their characteristics in practical applications will be crucial to the feasibility of developing efficient and scalable quantum computers.
At KIT’s Physikalisches Institut, doctoral researchers Ioannis Karapatzakis and Jeremias Resch have investigated how to precisely control a special defect in diamonds known as a tin-vacancy (SnV) center. Their work was part of two projects funded by Germany’s Federal Ministry of Education and Research: QuantumRepeater.Link (QR.X) for secure fiber-based quantum communication and SPINNING, which aims to develop a diamond spin-photon-based quantum computer.
“A defect in the lattice structure of a diamond’s carbon atoms occurs when atoms are missing or are replaced by other atoms such as tin,” said Karapatzakis. Such defects can be used as qubits for quantum communication because they have special optical and magnetic properties that enable states such as their electron spin to be manipulated using light or microwaves. The defects can then be used as stable qubits that can store and process information and couple it with photons.
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