A new study by applied physicists used a custom-designed microscope to examine supermoiré patterns in trilayer graphene.
Category: engineering
New technique improves multi-photon state generation
Quantum dots – semiconductor nanostructures that can emit single photons on demand – are considered among the most promising sources for photonic quantum computing. However, every quantum dot is slightly different and may emit a slightly different color. This means that, to produce multi-photon states we cannot use multiple quantum dots. Usually, researchers use a single quantum dot and multiplex the emission into different spatial and temporal modes, using a fast electro-optic modulator. Now here comes the technological challenge: faster electro-optic modulators are expensive and often require very customized engineering. To add to that, it may not be very efficient, which introduces unwanted losses in the system.
The international research team, led by Vikas Remesh from the Photonics Group at the Department of Experimental Physics of the University of Innsbruck and involving researchers from the University of Cambridge, Johannes Kepler University Linz, and other institutions, has now demonstrated an elegant solution that sidesteps these limitations. Their approach uses a purely optical technique called stimulated two-photon excitation to generate streams of photons in different polarization states directly from a quantum dot without requiring any active switching components. The team demonstrated their technique by generating high-quality two-photon states with excellent single-photon properties.
“The method works by first exciting the quantum dot with precisely timed laser pulses to create a biexciton state, followed by polarization-controlled stimulation pulses that deterministically trigger photon emission in the desired polarization”, explain Yusuf Karli and Iker Avila Arenas, the study’s first authors. “It was a fantastic experience for me to work in the photonics group for my master’s thesis, remembers Iker Avila Arenas, who was part of 2022–2024 cohort of the Erasmus Mundus Joint Master’s program in Photonics for Security Reliability and Safety and spent 6 months in Innsbruck.
What makes this approach particularly elegant is that we have moved the complexity from expensive, loss-inducing electronic components after the single photon emission to the optical excitation stage, and it is a significant step forward in making quantum dot sources more practical for real-world applications, notes Vikas Remesh, the study’s lead researcher. Looking ahead, the researchers envision extending the technique to generate photons with arbitrary linear polarization states using specially engineered quantum dots.
The study has immediate applications in secure quantum key distribution protocols, where multiple independent photon streams can enable simultaneous secure communication with different parties, and in multi-photon interference experiments which are very important to test even the fundamental principles of quantum mechanics, explains Gregor Weihs, head of the photonics research group in Innsbruck.
Using Grover’s algorithm to efficiently prepare collective quantum states in optical cavities
The reliable engineering of quantum states, particularly those involving several particles, is central to the development of various quantum technologies, including quantum computers, sensors and communication systems. These collective quantum states include so-called Dicke and Greenberger-Horne-Zeilinger (GHZ) states, multipartite entangled states that can be leveraged to collect precise measurements, to correct errors made by quantum computers and to enable communication between remote devices leveraging quantum mechanical effects.
Bioelectrosynthesis platform enables switch-like, precision control of cell signaling
Cells use various signaling molecules to regulate the nervous, immune, and vascular systems. Among these, nitric oxide (NO) and ammonia (NH₃) play important roles, but their chemical instability and gaseous nature make them difficult to generate or control externally.
A KAIST research team has developed a platform that generates specific signaling molecules in situ from a single precursor under an applied electrical signal, enabling switch-like, precise spatiotemporal control of cellular responses. This approach could provide a foundation for future medical technologies such as electroceuticals, electrogenetics, and personalized cell therapies.
The research team led by Professor Jimin Park from the Department of Chemical and Biomolecular Engineering, in collaboration with Professor Jihan Kim’s group, has developed a bioelectrosynthesis platform capable of producing either nitric oxide or ammonia on demand using only an electrical signal. The platform allows control over the timing, spatial range, and duration of cell responses.
Finding clarity in the noise: New approach recovers hidden signals at the nanoscale
In the world of nanotechnology, seeing clearly isn’t easy. It’s even harder when you’re trying to understand how a material’s properties relate to its structure at the nanoscale. Tools like piezoresponse force microscopy (PFM) help scientists peer into the nanoscale functionality of materials, revealing how they respond to electric fields. But those signals are often buried in noise, especially in instances where the most interesting physics happens.
Now, researchers at Georgia Tech have developed a powerful new method to extract meaningful information from even the noisiest data, or when, alternatively, the response of the material is the smallest. Their approach, which combines physical modeling with advanced statistical reconstruction, could significantly improve the accuracy and confidence of nanoscale measurement properties.
The team’s findings, led by Nazanin Bassiri-Gharb, Harris Saunders, Jr. Chair and Professor in the George W. Woodruff School of Mechanical Engineering and School of Materials Science and Engineering (MSE), are reported in Small Methods.
Progress and Perspectives in 2D Piezoelectric Materials for Piezotronics and Piezo‐Phototronics
The emergence of two-dimensional (2D) materials has catalyzed significant advancements in the fields of piezotronics and piezo-phototronics, owing to their exceptional mechanical, electronic, and optical properties. This review provides a comprehensive examination of key 2D piezoelectric and piezo-phototronic materials, including transition metal dichalcogenides, hexagonal boron nitride (h-BN), and phosphorene, with an emphasis on their unique advantages and recent research progress. The underlying principles of piezotronics and piezo-phototronics in 2D materials is discussed, focusing on the fundamental mechanisms which enable these phenomena. Additionally, it is analyzed factors affecting piezoelectric and piezo-photoelectric properties, with a particular focus on the intrinsic piezoelectricity of 2D materials and the enhancement of out-of-plane polarization through various modulation techniques and materials engineering approaches. The potential applications of these materials are explored from piezoelectric nanogenerators to piezo-phototronic devices and healthcare. This review addresses future challenges and opportunities, highlighting the transformative impact of 2D materials on the development of next-generation electronic, optoelectronic, and biomedical devices.
This review examines advancements in 2D materials, focusing on their applications in piezotronics and piezo-phototronics. It discusses key materials like TMDs, h-BN, and phosphorene, highlighting their unique mechanical, electronic, and optical properties. The review delves into the mechanisms of piezoelectricity, explores applications such as nanogenerators and biomedical devices, and describes the future and challenges in 3D integration of 2D materials.
Chinese scientists create tool to precisely edit millions of DNA segments
The new programmable chromosome engineering systems can manipulate DNA bases with 3.5 times more efficiency than original enzyme editor.
Quantum dot technique improves multi-photon state generation
A photonics research group co-led by Gregor Weihs of the University of Innsbruck has developed a new technique for generating multi-photon states from quantum dots that overcomes the limitations of conventional approaches. This has immediate applications in secure quantum key distribution protocols, where it can enable simultaneous secure communication with different parties.
Quantum dots—semiconductor nanostructures that can emit single photons on demand—are considered among the most promising sources for photonic quantum computing. However, every quantum dot is slightly different and may emit a slightly different color. This means that to produce multi-photon states, we cannot use multiple quantum dots.
Usually, researchers use a single quantum dot and multiplex the emission into different spatial and temporal modes, using a fast electro-optic modulator. The technological challenge is that faster electro-optic modulators are expensive and often require very customized engineering. To add to that, they may not be very efficient, which introduces unwanted losses into the system.
