Quantum Optics
The quantum properties of the nitrogen-vacancy (NV) center defect in diamond are being pursued as building blocks for quantum-enhanced technologies. Addressing and manipulating the defects, however, typically requires bulk optics, which could limit scalability. Siyushev et al. developed an on-chip technique in which the NV center is detected optoelectronically. Such a detection and manipulation method offers a route to develop an integrated platform for scalable quantum-based sensing technologies.
Science , this issue p. [728][1]
[1]: /lookup/doi/10.1126/science.aav2789
Quantum Optics
The quantum properties of the nitrogen-vacancy (NV) center defect in diamond are being pursued as building blocks for quantum-enhanced technologies. Addressing and manipulating the defects, however, typically requires bulk optics, which could limit scalability. Siyushev et al. developed an on-chip technique in which the NV center is detected optoelectronically. Such a detection and manipulation method offers a route to develop an integrated platform for scalable quantum-based sensing technologies.
Point defects in diamond, particularly nitrogen-vacancy (NV) centers, have emerged as powerful tools for a broad range of quantum technologies. These defects are promising candidates for quantum information science, serving as deterministic single-photon sources and solid-state quantum memories. They have also been employed as nanoscale quantum sensors to detect various physical quantities, including magnetic fields, electric fields, and temperature, owing to their long spin coherence time at room temperature. Development of these diamond-based quantum technologies has been rapidly boosted by a recent quantum leap in nanofabrication technologies for high-quality single-crystal diamond. Incorporating these color centers into diamond nanostructures with mature integrated photonics provides a promising route to build scalable and practical systems for quantum applications. This review discusses recent progress and challenges in the hybrid integration of diamond color centers on cutting-edge photonic platforms. Nitrogen-vacancy centers in diamond have emerged as powerful tools for a broad range of quantum technologies. This review discusses recent progress and challenges in the hybrid integration of diamond color centers on cutting-edge photonic platforms.
Quantum Optics
The development of scalable quantum systems will require the ability to control the interactions between the individual quantum building blocks of the system. Evans et al. used a pair of silicon vacancy centers embedded in a diamond nanocavity to show that interactions between the quantum emitters can be mediated optically (see the Perspective by Lodahl). Such optical control provides a speed advantage as well as the potential to develop an integrated platform for future quantum communication and quantum networking.
Science , this issue p. [662][1]; see also p. [646][2]
[1]: /lookup/doi/10.1126/science.aau4691
[2]: /lookup/doi/10.1126/science.aav3076
Nitrogen-vacancy (NV) centers in diamond have become an important instrument for quantum sensing and quantum information science. However, the readout of NV spin state requires bulky optical setups, limiting fabrication of miniaturized compact devices for practical use. Here we realized photoelectrical detection of magnetic resonance as well as Rabi oscillations on a single-defect level. Furthermore, photoelectrical imaging of individual NV centers at room temperature was demonstrated, surpassing conventional optical readout methods by providing high imaging contrast and signal-to-noise ratio. These results pave the way toward fully integrated quantum diamond devices.
Integrated photonic circuits promise to be foundational for applications in quantum information and sensing technologies, through their ability to confine and manipulate light. A key role in such technologies may be played by spin-active quantum emitters, which can be used to store quantum information or as sensitive probes of the local environment. A leading candidate is the negatively charged nitrogen vacancy (NV−) diamond color center, whose ground spin state can be optically read out, exhibiting long (≈1 ms) coherence times at room temperature. These properties have driven research toward the integration of photonic circuits in the bulk of diamond with the development of techniques allowing fabrication of optical waveguides. In particular, femtosecond laser writing has emerged as a powerful technique, capable of writing light guiding structures with 3D configurations as well as creating NV complexes. In this Perspective, the physical mechanisms behind laser fabrication in diamond will be reviewed. The properties of waveguides, single- and ensemble-NV centers, will be analyzed, together with the possibility to combine such structures in integrated photonic devices, which can find direct application in quantum information and sensing.
Quantum Information
Certain defects in diamond are among the most promising physical implementations of qubits, the building blocks of quantum computers. However, identifying a defect with balanced properties is tricky: Nitrogen vacancy centers have a long lifetime but comparatively poor optical properties, whereas negatively charged silicon vacancy centers have the opposite characteristics. Rose et al. used careful materials engineering to stabilize the neutral charge state of silicon vacancy centers and found that they combine long coherence times with excellent optical properties.
Science , this issue p. [60][1]
[1]: /lookup/doi/10.1126/science.aao0290
Quantum sensors encompass a diverse class of devices that exploit quantum coherence to detect weak or nanoscale signals. As their behavior is tied to physical constants, quantum sensors can achieve accuracy, repeatability, and precision approaching fundamental limits [1, 2]. As a result, these sensors have shown utility in a wide range of applications in both science and engineering leading to innovations. Among many solid-state spin systems, nitrogen-vacancy (NV) centers in diamonds have attracted considerable attention as a leading platform in many fields of quantum technologies, from quantum sensing to information processing and communication applications. They have superior physical properties, and their quantum coherence is preserved even at room temperature. The energy levels of NV centers are sensitive to magnetic fields, electric fields, strain, and temperature, and the spatial resolution is scalable from nanometers to millimeters. Therefore, diamond quantum sensors are distinctive sensors with multimodality and span scalable application fields. To realize an ideal quantum sensor for applications, the technical challenges in the sensor materials and the quantum control techniques, such as coherent microwave spin manipulation, effective optical spin-state initialization, and readout, have been developed. This chapter briefly explains the sensing principle using NV centers and then introduces sensor systems for biomedical applications, and monitoring of batteries for electric vehicles and internal power devices.