Building Blocks for Quantum Network Based on Group‐IV Split‐Vacancy Centers in Diamond

Abstract

One ultimate goal of quantum information processing is to construct a quantum network for direct sharing of quantum information between distant parties based on stationary qubits for information storage and flying qubits for information transmission. This requires long‐lived quantum memories, efficient light–matter interface, and deterministic quantum gate operations. Among matter qubits, the electron spin of nitrogen vacancy center in diamond is an appealing option for its long coherence time at room temperature, deterministic microwave control, and optical preparation and readout of the qubit. However, its poor optical properties, including weak zero‐phonon‐line emission and large spectral diffusion, limit its potential for large‐scale deployment in quantum nodes. This has motivated the investigation for alternative quantum emitters that combine long‐time memory and coherent optical properties together. The emerging group‐IV split‐vacancy color centers in diamond, such as silicon‐vacancy, germanium‐vacancy, tin‐vacancy, and lead‐vacancy centers, are promising candidates of this ongoing exploration. These quantum emitters simultaneously possess microsecond spin coherence time and optically bright transitions with narrow linewidths. This review reports recent efforts on extending the spin coherence time of these color centers via temperature, strain, and charge control, which paves the road towards constructing solid‐based matter–photon interface for quantum network applications.

Quantum Plasmonics: Energy Transport Through Plasmonic Gap

“…[12,33,[57][58][59] For example, coherency, entanglement, and tunneling can be further explored in quantum interferencebased devices, [60,61] single-photon emitters and detectors, [62,63] and quantum networks. [64][65][66][67] The quantum effect is explained further (in terms of the sub-nanometer size gap between two resonators) in the last section of this review. As discussed at length in the literature, plasmon coupling can occur over a 5 nm gap distance between plasmon dimers; thus, it is categorized as belonging to the classical regime.…”

Phonon sidebands of color centers in hexagonal boron nitride

“…Color centers in wide bandgap semiconductors, most notably diamond and SiC, with atom like behavior and favorable spin properties, have long held potential for quantum photonic technologies, such as single photon sources and spin qubits. [1][2][3] More recently, color centres in hexagonal boron nitride (hBN) [4][5][6] have emerged as an alternative pathway for fundamental studies and the rapid progress reflects the wide interest and potential of this material system. These defects span a wide spectral range, from the UV to the near-infrared 5,[7][8][9][10] and have attractive properties for quantum optics, including narrow linewidth, fast radiative recombination, stable emission and a relatively high fraction of photons emitted into the zero phonon line (ZPL).…”

Effect of Reactive Ion Etching on the Luminescence of GeV Color Centers in CVD Diamond Nanocrystals

“…Impurity-vacancy color centers in nanodiamonds (NDs) have attracted the attention of researchers as atom-like emitters for optical quantum technologies, biomedical markers, and temperature nanosensors [1][2][3][4][5][6]. Negatively charged germanium-vacancy centers (GeV − ) with zero phonon line (ZPL) at a wavelength of ~602 nm at room temperature are among the most promising emitting centers [1,[7][8][9][10][11][12][13]. The GeV − center is an interstitial point defect where a germanium atom is positioned midway between two adjacent missing carbon atoms in the diamond lattice with the diamond <111> axis as the principal [1].…”