A research team at UNIST has realized a single quantum light source that operates using electrical signals while reducing photon energy fluctuations. In quantum technology, which uses single photons as the unit of information, photon energy stability is a critical condition; this study presented a structure capable of simultaneously ensuring electrical control and light source purity.

UNIST announced on the 23rd that a research team led by Professors Sun Namgung and Jehyeong Kim of the Department of Physics has developed a high-purity single-quantum light source based on a 2D semiconductor that suppresses the Stark effect. The research results were published online in the international academic journal 'Nano Letters' on March 11. Researchers Satyabrat Behera and Jongseong Moon participated as first authors in this study.

A single quantum light source is a light source that emits photons one by one for a very short duration. In quantum computing or quantum cryptography, this single photon is utilized as the smallest unit of information. However, when voltage is applied to turn a light source on and off, the Stark effect may occur, which changes the energy of the emitted photons. In this case, interference between photons becomes difficult, which can reduce the performance of quantum information processing.

To reduce this, the research team placed tungsten diselenide (WSe₂), a two-dimensional semiconductor material, on top of pointed silicon nanopyramids and designed it so that a fine air layer is formed between the silicon and the semiconductor. This air layer reduces the electric field transmitted to the semiconductor to about one-twentieth of the level of the periphery, thereby reducing changes in photon energy. In addition, a high-quality insulating layer was added to suppress background luminescence caused by surrounding defects.

The purity of the light source has also been improved. As a result of the study, the probability value indicating single-photon emission characteristics was measured at 0.06. Generally, if this value is 0.5 or lower, it is classified as a single-quantum light source, and the closer it is to 0, the higher the probability that only one photon is emitted at a time. The research team believes that the insulating layer contributed to the improvement in purity by reducing background luminescence.

This achievement is significant in that it demonstrates the potential for application in the development of chip-based quantum communication, photon quantum computing, and quantum optical sensors, based on compatibility with silicon semiconductor processes. It is evaluated as a technology that goes beyond merely improving the performance of individual light sources and can serve as a foundational technology for the development of quantum devices that require the integration of multiple light sources onto a single chip.