Non-invasive bioinert room-temperature quantum sensor from silicon carbide qubits

The article Non-invasive bioinert room-temperature quantum sensor from silicon carbide qubits explores the development of a new type of quantum sensor based on divacancy qubits in silicon carbide (SiC). The study focuses on creating a room-temperature, bioinert quantum sensor suitable for biological applications, particularly in bioimaging, radical detection, and nanoscale nuclear spin sensing.

Key points from the article include:

1. Quantum Sensor Design: The sensor uses alkene-terminated SiC hosting divacancy qubits located just below the surface. This configuration ensures stable operation with minimal interference from biological environments, as SiC is bioinert. The qubits are excited and read out at near-infrared wavelengths, avoiding the absorption issues common in biological systems, which often affect green light.

2. Surface Treatment: The success of the sensor depends on the surface termination of SiC. Alkene modification (CH2=CHC11H23) was found to reduce interface defects significantly compared to conventional oxidation methods. This modification forms a hydrophobic layer that protects the SiC surface from external environmental damage, ensuring stable qubit operation. Furthermore, this surface can be functionalized for specific bioapplications by replacing the alkene groups with hydrophilic functional groups like alcohol.

3. Defect Types and Stability: The study compares different types of defects in SiC, particularly focusing on the divacancy defects, which are stable and have excellent properties for quantum sensing. These divacancies offer long coherence times and high optical readout contrasts, making them suitable for use as quantum sensors. The study also discusses challenges with other defects, such as carbon clusters, which are unsuitable for quantum applications due to their stochastic nature.

4. Quantum Sensing Protocols: The sensor demonstrated successful use in spin-relaxometry and quantum nuclear magnetic resonance (qNMR) measurements, with sensitivity of approximately 13 nT/√Hz. The experiments used gadolinium-based complexes (Gd-DO3A) to simulate radical detection, showing that the divacancy qubit sensor could detect paramagnetic species efficiently.

5. Room-Temperature Operation: A significant advantage of this quantum sensor is its operation at room temperature, which eliminates the need for energy-consuming cooling systems. This makes the sensor suitable for practical in vivo biological applications, including real-time monitoring of biological processes at the nanoscale.

6. Future Applications: The alkene-terminated SiC sensor has potential for use in quantum simulation and optoelectronics. The study also explores its ability to serve as a platform for observing and controlling quantum systems in biological settings and high-power optoelectronic devices.

In conclusion, this research presents a promising advancement in room-temperature quantum sensing, combining the bioinert properties of SiC with the stability of divacancy qubits. The sensor's ability to operate at room temperature with minimal interference from biological systems makes it an excellent candidate for applications in biological and medical fields.