Direct-Write Quantum Calligraphy in Monolayer Semiconductors

Naval Research Laboratory, Washington, DC and Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio

In contrast with conventional light-emitting diodes (LEDs) that emit billions of photons simultaneously to form a steady stream of light, a single photon emitter (SPE) generates exactly one photon on demand, with each photon indistinguishable from another. These characteristics are essential for photon-based quantum technologies under development. In addition, such capabilities should be realized in a material platform that enables precise, repeatable placement of SPEs in a fully scalable fashion compatible with existing semiconductor chip manufacturing.

(a) Illustration showing an AFM tip indenting the TMD/polymer structure to introduce local strain. (b) Patterned single photon emission in WSe₂ induced by AFM indentation of the letters NRL and AFRL. (c) AFM indents produce single photon emitter “ornaments” on a monolayer WSe₂ “Christmas tree.”

Researchers developed a way to directly write quantum light sources — which emit a single photon of light at a time — into monolayer semiconductors such as tungsten diselenide (WSe₂). An atomic force microscope (AFM) was used to create nanoscale depressions or indents in a single monolayer of WSe₂ on a polymer film substrate. A highly localized strain field is produced around the nano-indent, creating the single photon emitter state in the WSe₂. Time-correlated measurements of this light emission confirmed the true single photon nature of these states. These emitters are bright, producing high rates of single photons, and spectrally stable — key requirements for emerging applications.

This quantum calligraphy allows deterministic placement and real-time design of arbitrary patterns of SPEs for facile coupling with photonic waveguides, cavities, and plasmonic structures. A nano-imprinting approach is effective in creating large arrays or patterns of quantum emitters for wafer-scale manufacturing of quantum photonic systems.

In addition to enabling versatile placement of SPEs, these results present a general methodology for imparting strain into two-dimensional (2D) materials with nanometer-scale precision, providing an invaluable tool for further investigations and future applications of strain engineering of 2D devices.

Quantum computation on a chip provides onboard capability to rapidly analyze very large data sets acquired by sensor arrays, so that the entire data set does not have to be transmitted, reducing bandwidth requirements.

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