Quantum computing platforms have long relied on photons, or particles of light, to carry information, primarily due to their speed and low interaction with the environment. However, photons inherently suffer from randomness in their behavior, leading to probabilistic outcomes during quantum operations that challenge error correction and scalability. Addressing this limitation, a team comprising experimentalists from the Cleland Lab and theoreticians from the Jiang Group at the University of Chicago has unveiled a mechanism to exert deterministic control over the phase of phonons—quanta of mechanical vibrations—which can be thought of as the sound equivalent within the quantum realm.

Phonons, despite being less widespread in quantum computing discussions, possess advantageous qualities compared to photons. Unlike light, phonons are localized vibrational quanta, which, by virtue of their mechanical nature, do not readily leak into the vacuum of space, minimizing information loss. This quality could grant phonon-based quantum processors longer coherence times and better isolation from environmental noise. The team’s recent publication in Nature Physics details how phonons scattered off superconducting qubits can have their phase controlled deterministically, a feat that ensures quantum operations yield consistent, repeatable outcomes as opposed to the probabilistic results common in optical quantum systems.

Central to the research is the interaction between phonons and superconducting qubits—the quantum analogs of classical bits that form the foundation of quantum computation. By engineering precise coupling between these qubits and phonons, the UChicago team achieved control over the phonon phase, effectively turning phonons into reliable carriers of quantum information. This deterministic manipulation contrasts starkly with photon-based systems, where similar operations typically succeed only probabilistically, requiring complex measurement protocols to confirm success post-interaction. The novel phonon platform offers the enticing possibility of quantum operations that work “first time, every time,” potentially revolutionizing fidelity and efficiency in quantum circuits.

The implications of this deterministic control extend beyond mere manipulation. Conventional quantum systems are often hindered by probabilistic gates, leading to significant overhead in error correction and circuit complexity. By streamlining operations through deterministic phase gates mediated by phonons, quantum algorithms could be implemented with fewer resources and reduced error rates. The research also points toward scalable quantum architectures, since phonons can be confined and controlled within chip-based, solid-state devices, facilitating integration with existing quantum hardware technologies.

One limitation highlighted by the research concerns the lifetimes, or coherence times, of the phonons. Currently, engineered phonons under this protocol exhibit lifespans on the order of microseconds, restricted by their coupling to qubits—necessary for control but at the expense of rapid decay, akin to grabbing a ringing bell to silence it prematurely. Overcoming this hurdle stands as a significant next step; the team aims to extend phonon longevity by two orders of magnitude, which would enable phonons to sustain quantum information throughout more complex computational tasks.

Encouragingly, phonons decoupled from qubits theoretically possess coherence times stretching into seconds, vastly exceeding those of photons. This contrast arises because photons are electromagnetic waves that can leak into multiple external modes, while phonons remain confined in mechanical resonators without direct channels to vacuum loss. Realizing high-quality, well-isolated phononic resonators could thus unlock phonon coherence durations that fundamentally outpace light-based qubits, dramatically improving quantum memory and information retention capabilities.

In addition to phase control, the research incorporates number-resolving phonon detection—an advanced technique that counts individual phonons. This capability enriches the quantum toolbox by allowing precise measurements and manipulations of phonon quantum states, key for implementing error correction and complex quantum protocols. Such fine control over phonon populations and their quantum phases lays a robust foundation for building hybrid quantum systems that blend electronic, photonic, and phononic elements for optimized performance.

This phonon approach also dovetails with recent proposals from the same research group for novel quantum random access memory (qRAM) architectures, where compact and scalable quantum memories are crucial. By integrating deterministic phase gates and number-resolving detectors, future quantum processors could harness these phononic devices to realize fast, reliable memory and logic units essential for large-scale quantum computation.

Professor Andrew Cleland, leading the experimental effort, expressed cautious optimism about the phononic future. While acknowledging that photons remain dominant in current quantum computing efforts, Cleland emphasized that deterministic phonon platforms may present superior routes to predictability and scalability, particularly for chip-integrated, solid-state quantum technologies. Meanwhile, theoretical insights from Professor Liang Jiang underscore the broader field’s progress, noting rapid advancements in quantum phononics, including new architectures enabling compact devices with improved integrability.

Ultimately, this research heralds a transformative shift in quantum computing paradigms, replacing uncertainty with determinism at the quantum hardware level by leveraging the mechanical nature of sound. As the field advances toward extending phonon lifetimes and integrating these effects into fully coherent quantum processors, the vision of robust, scalable, and efficient quantum machines operating at the sound of their own quantum vibrations comes closer to reality.

Subject of Research: Quantum computing with deterministic phase control of phonons
Article Title: Acoustic phonon phase gates with number-resolving phonon detection
News Publication Date: 18-Sep-2025
Web References: https://doi.org/10.1038/s41567-025-03027-z
Image Credits: UChicago Pritzker School of Molecular Engineering / Joel Wintermantle
Keywords: Quantum computing

Conventional computing is founded on bits that hold a value of either 0 or 1, encoding information in a binary form. Quantum computers, on the other hand, leverage the phenomena of superposition and entanglement, allowing qubits to simultaneously represent states 0 and 1 in a complex, probabilistic mixture of states. This capacity enables quantum machines—such as a 20-qubit system—to represent over a million states at once, exponentially expanding their computational potential compared to classical computers. Unlocking this potential requires precise measurement of qubit states, a process inherently delicate due to the sensitivity of quantum information to external disturbances.

The act of measuring qubits demands the use of highly sensitive amplifiers capable of detecting extremely faint microwave signals emitted during quantum readout. These amplifiers must function with minimal noise to prevent disruption of the qubit’s fragile quantum state. However, existing amplification technologies generate heat and electromagnetic interference that contribute to qubit decoherence—the process by which the quantum system loses its coherence and thus its stored information. For decades, the search for more efficient, lower-noise quantum amplifiers has been a critical bottleneck in scaling quantum computing technology.

The team at Chalmers University, spearheaded by doctoral researcher Yin Zeng and supervised by professor Jan Grahn, has pushed the boundaries of amplifier technology by developing a transistor-based amplifier that consumes only a tenth of the power required by the best amplifiers currently available, without compromising on sensitivity or noise performance. This dramatic reduction in power usage directly addresses the decoherence problem, offering a pathway to larger, more stable quantum processors.

What fundamentally distinguishes this amplifier is its pulsed operation. Unlike conventional amplifiers that are continuously powered, this new technology activates only when qubit information needs to be read. This time-gated operation dramatically cuts unnecessary power consumption and minimizes thermal emissions during idle periods, thereby preserving the coherence of surrounding qubits.

Achieving rapid activation was no trivial feat. Quantum information is transmitted in pulses on nanosecond timescales, necessitating an amplifier that not only conserves energy but also responds with exceptional speed. Using an innovative approach involving genetic programming algorithms, the researchers engineered the amplifier’s control system to activate and reach full operational capacity within just 35 nanoseconds. This swift response aligns perfectly with the brief duration of qubit signal pulses, ensuring no loss in readout fidelity.

In addition to this smart pulse control, Chalmers researchers implemented a novel noise and amplification measurement technique tailored for pulse-operated low-noise microwave amplifiers. This breakthrough methodology enabled accurate characterization of the amplifier’s performance during the rapid switching intervals, a critical factor for verifying its suitability in quantum readout applications.

The implications of this development extend far beyond incremental improvements in amplifier technology. As quantum computers scale to thousands or even millions of qubits, heat dissipation from amplifiers operated continuously would pose an insurmountable barrier, causing widespread decoherence and limiting computational scale. The pulse-activated amplifier circumvents this hurdle by drastically reducing power consumption and thermal load, effectively unlocking new avenues for scaling quantum systems.

This advancement fits within the broader framework of Chalmers University’s commitment to quantum technology research, notably through the Wallenberg Centre for Quantum Technology, which fosters national efforts toward constructing scalable, practical quantum machines. The collaboration with Low Noise Factory AB, a leading manufacturer of ultra-low-noise microwave amplifiers, provided the industrial expertise necessary to transition experimental concepts into functional components suitable for real-world quantum computing platforms.

Funding from the Chalmers Centre for Wireless Infrastructure Technology and the Vinnova program "Smarter Electronic Systems" has been instrumental in supporting this research, underscoring the strategic importance of bridging fundamental science with technological innovation in the rapidly evolving quantum field.

Looking ahead, the practical adoption of this pulse-operated amplifier could redefine quantum computer architectures. By integrating energy-efficient, fast-responsive amplifiers, next-generation quantum systems can operate with more qubits, longer coherence times, and improved error rates, thereby bringing closer the realization of quantum advantages in various sectors including optimization problems, complex simulations, and secure communications.

The Chalmers team’s findings were published in the April 2025 issue of the IEEE Transactions on Microwave Theory and Techniques under the title “Pulsed HEMT LNA Operation for Qubit Readout.” This study lays the foundation for a new class of quantum measurement hardware essential for the next evolution in quantum computing.

Subject of Research:
Not applicable

Article Title:
Pulsed HEMT LNA Operation for Qubit Readout

News Publication Date:
April 17, 2025

Web References:
https://doi.org/10.1109/TMTT.2025.3556982
https://www.chalmers.se/en/centres/wacqt/
https://www.chalmers.se/en/centres/witech/

References:
Zeng, Y., Grahn, J., Stenarson, J., & Sobis, P. (2025). Pulsed HEMT LNA Operation for Qubit Readout. IEEE Transactions on Microwave Theory and Techniques. DOI: 10.1109/TMTT.2025.3556982

Image Credits:
Chalmers University of Technology | Yin Zeng | Maurizio Toselli

Keywords:
Quantum computing, qubit readout, low-noise amplifier, pulsed amplifier, semiconductor transistors, quantum decoherence, superposition, microwave technology, quantum measurement, scalability, energy-efficient amplifiers, genetic programming

The essence of this novel semiconductor lies in its ability to emit circularly polarized light, a trait that enables the transfer of information regarding the "handedness" of electrons. In contrast to traditional inorganic semiconductors, such as silicon, which exhibit symmetrical properties leading to non-directional electron movement, this innovative semiconductor harnesses the chiral characteristics of molecules. Chiral molecules, which can be thought of as mirror images, are prevalent in nature and play crucial roles in biological processes like DNA synthesis. Yet, leveraging this chirality within electronics has historically posed a challenge.

Through the integration of biophilic design principles into molecular architecture, the researchers succeeded in crafting a chiral semiconductor. This was accomplished by guiding stacks of semiconducting molecules to organize into either right-handed or left-handed spiral configurations. The findings from their research have been published in the prestigious journal Science, showcasing not just a notable academic achievement but also an important milestone for future technology.

One of the most promising applications for these chiral semiconductors is their use in display technology. Current display screens are notorious for wasting energy due to inefficiencies in light filtering processes. The chiral semiconductor introduced by these researchers naturally generates light in an orientation that could significantly mitigate such losses, thereby enhancing screen brightness and energy efficiency. This leap forward has profound implications, particularly as the demand for more sustainable technologies continues to grow.

Professor Sir Richard Friend, who collaborated in leading this innovative research from Cambridge’s Cavendish Laboratory, recounted, “When I began my journey with organic semiconductors, many remained skeptical about their potential. However, it is undeniable that they now form the backbone of display technology.” Highlighting the versatility of molecular materials, he likened the freedom to design unique structures to working with a limitless set of building blocks—a stark contrast to the constraints often imposed by rigid inorganic counterparts.

At the heart of this new semiconductor lies a material called triazatruxene (TAT), which self-assembles into a helical configuration, subsequently allowing electrons to spiral effectively along its structure. When stimulated by blue or ultraviolet light, this arrangement causes TAT to emit bright green light, characterized by strong circular polarization. Achieving such an effect in semiconductors had been a formidable challenge until this recent breakthrough, as articulated by Marco Preuss, co-first author from the Eindhoven University of Technology.

Through innovative adaptations in OLED fabrication techniques, the research team successfully integrated TAT into functional circularly polarized OLEDs (CP-OLEDs). These cutting-edge devices exhibited record levels of efficiency, brightness, and polarization, setting a new benchmark in the field. Co-first author Rituparno Chowdhury remarked, “By reengineering the conventional process for manufacturing OLEDs as we employ in smartphones, we’ve discovered a practical method for trapping a stable chiral structure within a non-crystallizing matrix.”

This research is culminative of a prolonged partnership between Sir Richard Friend’s research group and the team of Professor Bert Meijer from the Eindhoven University of Technology. Meijer commented on the significance of their collaboration by stating, “This breakthrough in developing a chiral semiconductor illustrates our meticulous approach to molecular design. We have successfully linked the chirality of our molecular structure to the electrons’ movement—a feat never previously accomplished on this scale.”

The implications of these chiral semiconductors extend far beyond display technologies. Envisioning a future driven by efficient quantum computing and advanced spintronics, these organic materials represent a crucial step forward in evolving electronic mechanisms. Within the growing $60 billion industry of organic semiconductors, this development signifies a turning point that may enhance not only the way we interact with technologies but also how we harness and process information.

Moreover, the work received substantial support from initiatives including the European Union’s Marie Curie Training Network and the European Research Council. Aided by this backing, the researchers are optimistic about tackling the forthcoming challenges and barriers that lie ahead in this rapidly advancing field.

This remarkable research, encapsulating years of collaboration and dedicated inquiry, has not only contributed to a burgeoning field of study but has also provided the scientific community with fresh insights into organic electronics. As the quest for optimizing performance and sustainability in electronic devices continues, this chiral semiconductor promises to be at the forefront of innovation, rooting its significance deeply in the evolution of future technologies.

In summary, this innovative leap in the domain of organic semiconductors enriches our understanding of electronics, presenting exciting potential for the future. By leveraging the intricate properties of molecular chirality, researchers are setting the stage for advanced applications that could redefine our approach to electronics and information technology, heralding in a new era characterized by efficiency and effectiveness.

Subject of Research: Chiral Semiconductors
Article Title: Circularly polarized electroluminescence from chiral supramolecular semiconductor thin films
News Publication Date: 14-Mar-2025
Web References: DOI Link
References: Science Journal
Image Credits: Samarpita Sen/Rituparno Chowdhury

Keywords

Organic semiconductors, display technology, light emitting diodes, molecular electronics, quantum computing, spintronics, semiconductors.