In a groundbreaking study, a team of researchers from the University of Washington has made a significant stride in the field of quantum technologies by observing and utilizing the unique vibrations of atoms. Led by Professor Mo Li, the team focused on studying the emission of light atoms when stimulated by a laser, leading to the detection of atomic vibrations referred to as “breathing.” This discovery holds great promise for the development of improved tools for various quantum applications.
At the core of quantum technologies lies quantum emitters (QEs), which enable the generation of individual quantum particles known as qubits. Qubits, akin to the information bits used in classical computing, possess distinct quantum properties that allow for computations far beyond the capabilities of classical computers. Typically, qubits are built using electrons or photons due to their unique quantum characteristics.
Professor Li and his team aimed to create a more advanced QE that could be seamlessly integrated into optical circuits. They began their research by utilizing tungsten diselenide, a molecule composed of tungsten and selenium, which they transformed into ultra-thin sheets, each just one atom thick. These sheets were then layered on top of each other and placed on nanopillars, resulting in regularly spaced quantum dots called “strain-induced quantum dots.” These quantum dots are semiconductor particles with unique electronic and optical properties, commonly employed in the construction of QEs for quantum applications.
By precisely applying laser light to one of these quantum dots, an electron is displaced from the nucleus of the tungsten diselenide atom, creating a transient quasiparticle known as an exciton. The exciton comprises a negatively charged electron and a positively charged hole in the opposing sheet. Due to their strong binding, the electron swiftly returns to the atom, releasing a single photon encoded with precise quantum information.
The successful production of consistent, high-quality photons capable of serving as qubits was an achievement in itself. However, during the analysis of the data, the researchers made an intriguing observation. Alongside the creation of photons, a quasiparticle called a phonon was also generated. Phonons are optomechanical phenomena arising from the vibration between atoms and are present in all forms of matter. They can be visualized as the “breath between atoms,” representing vibrations that occur at the atomic level.
In this study, phonons were generated through the vibration between the two atom-thin layers of tungsten diselenide, resembling tiny drumheads vibrating in relation to each other. The team discovered a close correlation between these phonons and the photons being generated. The vibrations caused by the phonons directly affected the recombination of the electron and the hole, consequently altering the emitted photon.
Remarkably, this study marked the first observation of phonons in this type of single-photon emitter system. The analysis of the emitted light spectrum unveiled evenly spaced peaks representing different quantum energy levels of the phonons. Each photon emitted by an exciton was found to be coupled with one or more phonons, which significantly influenced the optical properties of the emitted photon.
Moreover, the researchers successfully manipulated the phonon-exciton-photon interaction by applying an electrical voltage across the materials. By adjusting the voltage, they could control the interaction energy of the associated phonons and emitted photons, thereby encoding specific quantum information into a single photon.
Professor Li and his team aim to expand their research to include multiple emitters and their corresponding phonon states. This advancement would enable quantum emitters to communicate with each other, forming the basis for novel quantum circuitry. The future applications of this research encompass quantum computing, quantum communications, and quantum sensing.
The University of Washington team’s remarkable findings have opened up new possibilities in the field of quantum technology. By harnessing the intrinsic vibrations of atoms, researchers are paving the way for enhanced quantum tools with potential implications across various domains. This study, published in the journal Nature Nanotechnology, represents a significant milestone in the pursuit of quantum advancements and holds promise for the development of future quantum technologies.
