Latest Developments in Quantum Interface Research

Check out the latest from MIT EQuS and Lincoln Laboratory published in @NaturePhysics! In this work, we demonstrate a quantum interconnect using a waveguide to connect two superconducting, multi-qubit modules located in separate microwave packages. We emit and absorb microwave photons on demand and in a chosen direction between these modules using quantum entanglement and quantum interference. To optimize the emission and absorption protocol, we use a reinforcement learning algorithm to shape the photon for maximal absorption efficiency, exceeding 60% in both directions. By halting the emission process halfway through its duration, we generate remote entanglement between modules in the form of a four-qubit W state with concurrence exceeding 60%. This quantum network architecture enables all-to-all connectivity between non-local processors for modular, distributed, and extensible quantum computation. Read the full paper here: https://lnkd.in/eN4MagvU (paywall), view-only link https://rdcu.be/eeuBF, or arXiv https://lnkd.in/ez3Xz7KT. See also the related MIT News article: https://lnkd.in/e_4pv8cs. Congratulations Aziza Almanakly, Beatriz Yankelevich, and all co-authors with the MIT EQuS Group and MIT Lincoln Laboratory! Massachusetts Institute of Technology, MIT Center for Quantum Engineering, MIT EECS, MIT Department of Physics, MIT School of Engineering, MIT School of Science, Research Laboratory of Electronics at MIT, MIT Lincoln Laboratory, MIT xPRO, Will Oliver

Scientists Discover New Method to Entangle Light and Sound Researchers at the Max Planck Institute for the Science of Light (MPL) have unveiled a groundbreaking technique for entangling photons (quanta of light) with acoustic phonons (traveling sound waves). Published in Physical Review Letters, this study demonstrates a robust method of creating quantum entanglement that resists external noise—overcoming a significant challenge in advancing quantum technologies. Why It Matters Quantum entanglement, where particles are interconnected so the state of one influences the other regardless of distance, is fundamental to many emerging technologies, including: • Secure Quantum Communications: Enhancing encryption through unbreakable quantum protocols. • High-Dimensional Quantum Computing: Enabling advanced computational systems capable of solving complex problems. While photon entanglement is well-established, entangling photons with phonons presents unique advantages, particularly in bridging fast optical signals with slower, localized acoustic waves. Breakthrough in Optoacoustic Entanglement The MPL team developed a new optoacoustic entanglement scheme that pairs photons with phonons. Key highlights include: 1. Enhanced Robustness: The entanglement demonstrated resistance to external noise, addressing a critical limitation of most quantum systems. 2. Efficient Coupling: By leveraging nonlinear optical methods, scientists efficiently linked the fast propagation of photons with the localized nature of phonons. 3. Versatility: This approach enables the transfer of quantum information between light and sound, creating a hybrid platform for various quantum applications. Applications of Light-Sound Entanglement 1. Quantum Memory: Phonons, with their slower speeds and longer lifetimes, can act as quantum storage for information carried by photons. 2. Hybrid Quantum Networks: Connecting quantum systems operating at different scales, such as optical and mechanical devices. 3. Resilient Quantum Devices: Building systems that are less prone to environmental disturbances, enabling practical quantum computing and communication technologies. Future Implications The ability to entangle light and sound opens the door to: • Integrating quantum technologies with classical systems. • Developing ultra-stable quantum networks that operate across varying mediums. • Expanding the range of materials and mechanisms available for quantum device engineering. This breakthrough represents a critical step toward scalable and resilient quantum systems, bridging the gap between fast optical data transmission and long-lived acoustic storage. It highlights the transformative potential of interdisciplinary quantum research.

In our new paper published in Nature Portfolio Light: Science & Applications, entitled "𝗔𝘁𝘁𝗼𝘀𝗲𝗰𝗼𝗻𝗱 𝗾𝘂𝗮𝗻𝘁𝘂𝗺 𝘂𝗻𝗰𝗲𝗿𝘁𝗮𝗶𝗻𝘁𝘆 𝗱𝘆𝗻𝗮𝗺𝗶𝗰𝘀 𝗮𝗻𝗱 𝘂𝗹𝘁𝗿𝗮𝗳𝗮𝘀𝘁 𝘀𝗾𝘂𝗲𝗲𝘇𝗲𝗱 𝗹𝗶𝗴𝗵𝘁 𝗳𝗼𝗿 𝗾𝘂𝗮𝗻𝘁𝘂𝗺 𝗰𝗼𝗺𝗺𝘂𝗻𝗶𝗰𝗮𝘁𝗶𝗼𝗻” We demonstrate the following breakthroughs 1-   𝗨𝗹𝘁𝗿𝗮𝗳𝗮𝘀𝘁 𝗦𝗾𝘂𝗲𝗲𝘇𝗲𝗱 𝗟𝗶𝗴𝗵𝘁 𝗚𝗲𝗻𝗲𝗿𝗮𝘁𝗶𝗼𝗻 We generated the ultrafast squeezed light pulses through a nonlinear four-wave mixing process, producing some of the shortest quantum-synthesized light pulses to date. 2-   𝗥𝗲𝗮𝗹-𝗧𝗶𝗺𝗲 𝗤𝘂𝗮𝗻𝘁𝘂𝗺 𝗨𝗻𝗰𝗲𝗿𝘁𝗮𝗶𝗻𝘁𝘆 𝗗𝘆𝗻𝗮𝗺𝗶𝗰𝘀 𝗖𝗼𝗻𝘁𝗿𝗼𝗹 By controlling and switching between amplitude and phase squeezing, the team revealed that quantum uncertainty is a dynamic, tunable property rather than a fixed limit, a breakthrough with far-reaching implications. 3-   𝗣𝗲𝘁𝗮𝗵𝗲𝗿𝘁𝘇-𝗦𝗰𝗮𝗹𝗲 𝗤𝘂𝗮𝗻𝘁𝘂𝗺 𝗖𝗼𝗺𝗺𝘂𝗻𝗶𝗰𝗮𝘁𝗶𝗼𝗻 To showcase the potential, we demonstrated a novel petahertz-scale secure quantum communication protocol. By encoding data directly onto ultrafast squeezed waveforms, the scheme provides multiple layers of protection against eavesdropping and could underpin the future of high-speed encrypted communication networks. Looks like in this International Year of Quantum Science and Technology, with great efforts from many groups, we see the birth of the new field of #𝗨𝗹𝘁𝗿𝗮𝗳𝗮𝘀𝘁 𝗤𝘂𝗮𝗻𝘁𝘂𝗺 𝗢𝗽𝘁𝗶𝗰𝘀, Thanks for the excellent team effort from my colleagues Mohamed Sennary, Javier Rivera-Dean, Mohamed ElKabbash, Maciej Lewenstein from ICFO Vladimir Pervak from Ludwig-Maximilians-Universität München and Max Planck Institute of Quantum Optics https://lnkd.in/gWG2-vep Macij and Pervek.

DARPA’s QuANET researchers have demonstrated the first functioning quantum-augmented network. Less than a year ago DARPA launched a new program called QuANET (Quantum-Augmented Network) to answer: Can we combine the best of classical and quantum communications to create a vastly more secure, resilient network? QuANET’s mission is to integrate quantum links into today’s internet infrastructure. The goal is to marry the unique “covertness” (stealth) of quantum communications with the ubiquity and scale of classical networks . And QuANET researchers just demonstrated a functioning quantum-augmented network. They encoded and sent images as quantum data on a beam of “squeezed” light. The initial attempt took five minutes, but after real-time optimization the team slashed it to just 0.7 milliseconds (~6.8 Mbps) – fast enough to stream HD video. This rapid improvement, achieved only ~10 months into the project, shows how quickly quantum networking is moving from lab theory toward practical reality. From a cybersecurity standpoint, QuANET could be impactful. Even the most advanced classical networks today remain vulnerable to relentless cyberattacks, whereas quantum communication can inherently bolster resilience – any eavesdropping or tampering attempt would disturb the quantum data and be detected. By embedding quantum encryption and transmissions into network architectures, QuANET aims to make critical infrastructure much harder to compromise. I find QuANET’s emergence to be a significant milestone. For years, quantum networking (even quantum-augmented networking) have been a niche research topic – often confined to laboratory demos or isolated testbeds. Now we’re seeing a major R&D agency actively bridging quantum and classical networks, which is a big leap toward mainstream adoption. It’s not every day you hear about an ASCII-art cat being beamed over a quantum link. More importantly, it shows that quantum-secure communication is becoming a reality. #Quantum #QuantumNetworking #PQC https://lnkd.in/gEhszfaC

Delighted to share some work we've been developing over the past months! 📄 🔗🔗 https://lnkd.in/enXEQdDc 🔗🔗 ✨ Building on our previous research [https://lnkd.in/eCjCDv2D], we've explored a new direction for modular quantum computing with surface codes. The focus is on whether emission-based hardware can support fault-tolerant quantum error correction. The question we set out to answer: 🤔 📡 Can we distribute entanglement across modules without relying on slow and noisy two-qubit gates? 🔗 Our earlier work showed emission-based platforms were feasible but limited to thresholds of 0.16 % ⚡ Is there a more efficient protocol path forward? Our approach: 🎯 We propose single-shot GHZ state generation — creating the entangled states needed for stabilizer measurements directly, without Bell-pair fusion. The optical setup generates Bell pairs, W states, and GHZ states by simply observing photon detection patterns. Benchmarking on realistic hardware: 🧪 #DiamondColorCenters #QuantumHardware 🔴 We modeled this for diamond color-center platforms (what experimentalists are actually building) 🔴 Full noise modeling includes photon loss, detector efficiency, and circuit-level errors 🔴 Both photon-number-resolving and standard detectors analyzed The findings: 📊 We're grateful for what the analysis reveals about this architecture with circuit-level noise: 💎 Threshold of 0.24 % with photon-number-resolving detectors 💎 Threshold of 0.19 % with standard detectors 💎 These thresholds scale with hardware improvements — unlike previous approaches that saturated Why this matters: 🛣️ #FaultTolerance #ModularQuantumComputing #QuantumErrorCorrection This work suggests a practical pathway toward scalable modular quantum computers using hardware that's already being developed in labs. The protocols require only modest enhancements to existing emission-based setups. Looking ahead: 🔮 #ExperimentalQuantum #QuantumNetworks #DistributedQuantum We hope these results help guide the experimental community's next steps. We've tried to provide clear hardware targets and realistic thresholds that could inform near-term implementations. Special thanks to our collaborators at QuTech, Keio University, and OIST for making this collaborative effort possible. 🙏 Daniel Bhatti, Rikiya Kashiwagi, David Elkouss, Kazufumi Tanji, Wojciech Roga, Masahiro Takeoka #QuantumComputing #SurfaceCode #Photonics #ColorCenters #QuantumErrorCorrection #ModularArchitectures #QuantumInternet

PHOTON-INTERFACED SCALABLE QUANTUM NODES LINKING LIGHT AND MATTER The photon‑interfaced ten‑qubit register of trapped ions constitutes a potential advance in the development of scalable quantum network nodes. In this architecture, each ion in a ten‑qubit linear chain is individually entangled with a propagating photon, producing a sequential train of ion–photon Bell pairs with high fidelity. Previous experiments had only achieved this capability for one or two ions, making the extension to a full ten‑qubit register a meaningful step toward practical matter‑to‑light interfaces for distributed quantum information processing. The system operates by dynamically transporting ions into the mode of an optical cavity and driving a cavity‑mediated Raman transition that generates a single photon entangled with the ion’s internal qubit state. This procedure yields a time‑ordered photonic qubit stream in which each photon carries the quantum information of a distinct ion. The significance of this work lies in its direct response to a central challenge in quantum networking: the need to map the quantum state of a multi‑qubit matter register onto a set of photonic qubits that can propagate through optical fiber with low loss. Trapped ions serve as exceptionally coherent stationary qubits, but they cannot be transported between processors. Photons, by contrast, function as low‑loss flying qubits capable of transmitting quantum information over long distances. Ion–photon entanglement is therefore the essential mechanism for linking spatially separated ion‑based processors. Scaling this interface to ten ions establishes a clear path toward high‑rate, multiplexed entanglement distribution. This scaling is particularly relevant in light of recent long‑distance demonstrations in which multiple ions, each entangled with its own photon, were used to increase entanglement distribution rates over fiber links exceeding one hundred kilometers. Generating a rapid sequence of entangled photons—each correlated with a different ion—enables temporal multiplexing, which is indispensable for overcoming fiber loss and improving heralded entanglement rates. The ten‑ion photon‑interfaced register provides precisely the type of multiplexed matter‑to‑light source required for such architectures. Despite its importance, several technical challenges remain. Photon detection probabilities must be increased to support long‑distance networking without excessive repetition rates. Sequential ion shuttling introduces timing overhead and potential motional heating, and cavity alignment and stability become increasingly demanding as the register size grows. Maintaining spectral and temporal indistinguishability across the full photon train is essential for multi‑node entanglement generation and remains an active area of optimization. These challenges, however, represent engineering refinements rather than fundamental limitations. #DOI: https://lnkd.in/e5HRus5e

𝗠𝗮𝗶𝗻𝘁𝗮𝗶𝗻𝗶𝗻𝗴 𝗰𝗼𝗵𝗲𝗿𝗲𝗻𝗰𝗲 𝗶𝗻 𝘀𝘂𝗽𝗲𝗿𝗰𝗼𝗻𝗱𝘂𝗰𝘁𝗶𝗻𝗴 𝗾𝘂𝗮𝗻𝘁𝘂𝗺 𝗽𝗿𝗼𝗰𝗲𝘀𝘀𝗼𝗿𝘀 𝗶𝘀 𝗮 𝗰𝗼𝗻𝘀𝘁𝗮𝗻𝘁 𝗯𝗮𝘁𝘁𝗹𝗲. While many factors contribute to qubit decoherence, 𝗧𝘄𝗼-𝗟𝗲𝘃𝗲𝗹 𝗦𝘆𝘀𝘁𝗲𝗺 (𝗧𝗟𝗦) 𝗱𝗲𝗳𝗲𝗰𝘁𝘀 remain among the most 𝗳𝗿𝘂𝘀𝘁𝗿𝗮𝘁𝗶𝗻𝗴 𝗰𝗵𝗮𝗹𝗹𝗲𝗻𝗴𝗲𝘀. 🔹 𝗧𝗵𝗲 𝗣𝗿𝗼𝗯𝗹𝗲𝗺 𝗧𝗟𝗦 𝗱𝗲𝗳𝗲𝗰𝘁𝘀, typically found in the surfaces and interfaces of superconducting circuits, can r𝗲𝘀𝗼𝗻𝗮𝗻𝘁𝗹𝘆 𝗰𝗼𝘂𝗽𝗹𝗲 𝘄𝗶𝘁𝗵 𝗾𝘂𝗯𝗶𝘁𝘀, leading to 𝗶𝗻𝗰𝗿𝗲𝗮𝘀𝗲𝗱 𝗱𝗲𝗰𝗼𝗵𝗲𝗿𝗲𝗻𝗰𝗲 𝗮𝗻𝗱 𝗴𝗮𝘁𝗲 𝗲𝗿𝗿𝗼𝗿𝘀. These defects are particularly problematic due to their spatial and temporal instability, causing 𝘂𝗻𝗽𝗿𝗲𝗱𝗶𝗰𝘁𝗮𝗯𝗹𝗲 "𝗱𝗿𝗼𝗽𝗼𝘂𝘁𝘀" 𝗶𝗻 𝗾𝘂𝗯𝗶𝘁 𝗽𝗲𝗿𝗳𝗼𝗿𝗺𝗮𝗻𝗰𝗲. When it comes to mitigating TLS noise, several approaches exist: 🔹𝗛𝗮𝗿𝗱𝘄𝗮𝗿𝗲-𝗟𝗲𝘃𝗲𝗹 𝗦𝘁𝗿𝗮𝘁𝗲𝗴𝗶𝗲𝘀 - 𝗠𝗮𝘁𝗲𝗿𝗶𝗮𝗹 𝗘𝗻𝗴𝗶𝗻𝗲𝗲𝗿𝗶𝗻𝗴: High-purity materials and advanced fabrication techniques to reduce TLS density. - 𝗦𝘂𝗿𝗳𝗮𝗰𝗲 𝗧𝗿𝗲𝗮𝘁𝗺𝗲𝗻𝘁𝘀: Minimizing lossy interfaces where TLSs often reside. - 𝗖𝗶𝗿𝗰𝘂𝗶𝘁 𝗗𝗲𝘀𝗶𝗴𝗻: Engineering qubit circuits to minimize coupling to TLSs. 🔹𝗖𝗼𝗻𝘁𝗿𝗼𝗹 & 𝗦𝗼𝗳𝘁𝘄𝗮𝗿𝗲 𝗧𝗲𝗰𝗵𝗻𝗶𝗾𝘂𝗲𝘀 - 𝗤𝘂𝗯𝗶𝘁 𝗙𝗿𝗲𝗾𝘂𝗲𝗻𝗰𝘆 𝗧𝘂𝗻𝗶𝗻𝗴: Shifting qubit frequencies away from TLS resonances, widely used in tunable transmon architectures. - 𝗗𝘆𝗻𝗮𝗺𝗶𝗰 𝗗𝗲𝗰𝗼𝘂𝗽𝗹𝗶𝗻𝗴: Pulse sequences that average out the effect of TLS noise. - 𝗔𝗰𝘁𝗶𝘃𝗲 𝗙𝗲𝗲𝗱𝗯𝗮𝗰𝗸: Real-time monitoring and adaptive qubit control. While some of these techniques come with considerable overhead, new approaches are emerging to address the TLS challenge more efficiently: 🔹𝗧𝗵𝗲 𝗧𝗜𝗖-𝗧𝗔𝗤 𝗔𝗽𝗽𝗿𝗼𝗮𝗰𝗵: 𝗔 𝗡𝗲𝘄 𝗖𝗼𝗻𝘁𝗿𝗼𝗹 𝗦𝘁𝗿𝗮𝘁𝗲𝗴𝘆 The Siddiqi group just introduced a new technique called 𝗧𝗜𝗖-𝗧𝗔𝗤 (Targeted In-situ Control of TLS and Qubits): - 𝗦𝗶𝗻𝗴𝗹𝗲 𝗖𝗼𝗻𝘁𝗿𝗼𝗹 𝗟𝗶𝗻𝗲: Provides local and independent control of each qubit’s noise environment with a single on-chip control line. - 𝗘𝗹𝗲𝗰𝘁𝗿𝗶𝗰 𝗙𝗶𝗲𝗹𝗱 𝗧𝘂𝗻𝗶𝗻𝗴: Instead of shifting the qubit frequency, TIC-TAQ dynamically tunes TLSs away from the qubit frequency by applying a local electric field. - 𝗖𝗼𝗺𝗽𝗹𝗲𝗺𝗲𝗻𝘁𝗮𝗿𝘆 𝗧𝗲𝗰𝗵𝗻𝗶𝗾𝘂𝗲: Expected to enhance existing strategies for managing TLS-induced errors. 𝗧𝗜𝗖-𝗧𝗔𝗤 𝘀𝗵𝗼𝘄𝘀 𝗽𝗿𝗼𝗺𝗶𝘀𝗶𝗻𝗴 𝗿𝗲𝘀𝘂𝗹𝘁𝘀: - 36% Improvement in single-qubit error rates. - 17% Increase in qubit relaxation times (T₁). - 4x Suppression in TLS-induced performance outliers. 𝗪𝗵𝘆 𝗗𝗼𝗲𝘀 𝗧𝗵𝗶𝘀 𝗠𝗮𝘁𝘁𝗲𝗿? TLS defects are a roadblock on the path to fault-tolerant quantum computing. It’s great to see how hardware innovations and smart control techniques make a measurable impact. Are you more optimistic about hardware-based or control-based solutions for mitigating TLS noise? 📸 Image Credits: Larry Chen, Kan-Heng Lee et al. (arXiv, 2025)

Exploring the Quantum Frontier for 6G! Our latest work, "Harnessing Rydberg Atomic Receivers: From Quantum Physics to Wireless Communications", co-authored with Yuanbin Chen, Xufeng Guo, Chau Yuen, Yufei Zhao, Yong Liang Guan, Chong Meng Samson See, and Lajos Hanzo looks at the exciting integration of Rydberg atomic receivers into wireless communication systems. By leveraging principles of quantum mechanics, these receivers open unprecedented possibilities for ultra-sensitive signal detection and transformative applications in 6G networks. Superior Sensitivity: A staggering 44 dB SNR gain over conventional RF receivers. Extended Coverage: Up to 150 times range extension at extremely low power levels. Quantum-Driven Efficiency: Support for higher-order QAM with reduced error rates, reshaping how we envision low-power, high-performance wireless networks. The implications for 6G are immense—quantum technologies like Rydberg atomic receivers could redefine coverage, efficiency, and precision in wireless communication. More on the paper can be found here:

⚛️ Distributed Quantum Information Processing: A Review of Recent Progress 📑 Distributed quantum information processing seeks to overcome the scalability limitations of monolithic quantum devices by interconnecting multiple quantum processing nodes via classical and quantum communication. This approach extends the capabilities of individual devices, enabling access to larger problem instances and novel algorithmic techniques. Beyond increasing qubit counts, it also enables qualitatively new capabilities, such as joint measurements on multiple copies of high-dimensional quantum states. The distinction between single-copy and multi-copy access reveals important differences in task complexity and helps identify which computational problems stand to benefit from distributed quantum resources. At the same time, it highlights trade-offs between classical and quantum communication models and the practical challenges involved in realizing them experimentally. In this review, we contextualize recent developments by surveying the theoretical foundations of distributed quantum protocols and examining the experimental platforms and algorithmic applications that realize them in practice. ℹ️ Knörzer et al - 2025