Microwaves enhance diamond qubit control for quantum communication

Microwaves enhance diamond qubit control for quantum communication
by Robert Schreiber
Berlin, Germany (SPX) Oct 04, 2024

Quantum computing and communication are leading the charge toward faster, more secure data processing compared to classical technologies. At the core of quantum computers are qubits, the quantum equivalent of traditional bits, capable of storing and processing quantum information.

In traditional communication, information is transmitted using laser pulses through fiber optics, while quantum communication relies on individual photons. This makes data interception virtually impossible. Optically addressable qubits, which can be controlled by light, are key in quantum computing as they can store, process, and exchange information with photons.

The Challenge of Qubit Stability
A key hurdle in quantum computing is increasing the coherence time, which is the period a qubit can store information without losing stability. The ability to control qubits and maintain their coherence is critical to scaling up quantum computing technologies for practical use.

Researchers at Karlsruhe Institute of Technology (KIT), Ioannis Karapatzakis and Jeremias Resch, have been working on controlling a specific defect in diamonds, known as a tin-vacancy (SnV) center, which has unique optical and magnetic properties. Their research is part of two projects, QuantumRepeater.Link (QR.X) and SPINNING, funded by Germany's Federal Ministry of Education and Research. These initiatives focus on developing secure fiber-based quantum communication and quantum computers based on spin-photon interactions.

"A defect in a diamond's carbon lattice occurs when atoms are replaced by others, such as tin," explained Karapatzakis. "These defects serve as qubits because their electron spin can be manipulated by light or microwaves." By exploiting these defects, the team aimed to enhance the performance of diamond qubits in quantum communication.

Extending Coherence Time
Diamond qubits, which exist in the solid phase, are easier to manage compared to other quantum materials like atoms in vacuum. Karapatzakis and Resch succeeded in controlling the electron spins of tin-vacancy qubits using microwaves. According to Resch, "We increased the coherence times of diamond SnV centers to ten milliseconds, a significant improvement." This was achieved by using a technique called dynamical decoupling, which reduces interference.

The researchers also made significant strides by demonstrating that tin-vacancy defects can be efficiently controlled using superconducting waveguides. These waveguides direct microwaves to the defects without producing heat, crucial for qubit operation at temperatures near absolute zero. "Higher temperatures would render the qubits ineffective," added Karapatzakis.

To advance quantum communication, the next step involves transferring quantum states between qubits and photons. "With optical qubit readout and stable spectral properties, we've made a significant leap forward," said Resch. Their research on tin-vacancy centers in diamonds brings us closer to future secure and efficient quantum communication networks.

Research Report:Microwave Control of the Tin-Vacancy Spin Qubit in Diamond with a Superconducting Waveguide