Quantum Entanglement in Large-Scale Systems

A Dark State of 13,000 Entangled Spins Unlocks a Quantum Register Researchers have achieved a major breakthrough in quantum networking by entangling 13,000 nuclear spins within a gallium arsenide (GaAs) quantum dot system, successfully creating a scalable quantum register. This advancement could significantly improve secure quantum communication and long-distance quantum information transfer. Key Breakthrough: 13,000-Spin Quantum Register • Quantum registers are crucial for storing and transferring quantum information over long distances, but scalability and coherence have been major challenges. • The research team developed a quantum register using a network of nuclear spins, demonstrating stable and controllable entanglement across 13,000 qubits. • This marks a significant leap toward practical, large-scale quantum storage and enhances the potential for quantum networks. Why Quantum Dots Matter • Quantum dots are nano-sized semiconductor particles that can trap and control electrons, acting as quantum nodes in a future quantum internet. • They are valuable because they emit single photons, a key requirement for secure quantum communication and quantum computing. • To be truly effective, quantum networks need stable qubits that can interact with photons and store information without significant errors—a challenge that this research addresses. Implications for Quantum Technology • Ultra-Secure Quantum Networks: Scalable quantum registers could enable long-range entanglement, making quantum encryption even more secure. • More Reliable Quantum Computing: Storing information across a large number of nuclear spins enhances quantum memory stability, improving error correction. • Faster Quantum Information Processing: The ability to control thousands of entangled spins could lead to more efficient quantum operations. What’s Next? • Researchers will work on extending coherence times and improving error correction mechanisms to make this technology more practical for real-world quantum applications. • The next phase involves integrating quantum registers with photonic quantum networks, moving closer to a global quantum internet. By unlocking stable, large-scale entanglement within quantum dot systems, this discovery represents a major step toward building ultra-fast, secure quantum networks—bringing the vision of practical quantum communication closer to reality.

Breakthrough for the #quantum internet: For the first time a major telco provider has successfully conducted entangled photon experiments - on its own infrastructure. ➡️ 30 kilometers, 17 days, 99 per cent fidelity. Our teams at T-Labs have successfully transmitted entangled photons over a fiber-optic network. Over a distance comparable to travelling from Berlin to Potsdam. The system automatically compensated for changing environmental conditions in the network.   Together with our partner Qunnect we have demonstrated that quantum entanglement works reliably. The goal: a quantum internet that supports applications beyond secure point-to-point networks. Therefore, it is necessary to distribute the types of entangled photons. The so-called qubits, that are used for #QuantumComputing, sensors or memory. Polarization qubits, like the ones used for this test, are highly compatible with many quantum devices. But: they are difficult to stabilize in fibers.   From the lab to the streets of Berlin: This success is a decisive step towards the quantum internet. 🔬 It shows how existing telecommunications infrastructure can support the quantum technologies of tomorrow. This opens the door to new forms of communication.   Why does this matter for people and society?   🗨️ Improved communications: The quantum internet promises faster and more efficient long-distance communications. 🔐 Maximum security: Entanglement can be used in quantum key distribution protocols. Enabling ultra-secure communication links for enterprises and government institutions 💡Technological advancement: high-precision time synchronization for satellite networks and highly accurate sensing in industrial IoT environments will need entanglement.   Developing quantum technologies isn’t just a technical challenge. A #humancentered approach asks how these systems can be built to serve real needs and be part of everyday infrastructure. With 2025 designated as the International Year of Quantum Science and Technology, now is the time to move from research to readiness. Matheus Sena, Marc Geitz, Riccardo Pascotto, Dr. Oliver Holschke, Abdu Mudesir

🚨 Exciting #quantumcomputing alert! Now #QEC primitives actually make #quantumcomputers more powerful! 75 qubit GHZ state on a superconducting #QPU 🚨 In our latest work we address the elephant in the room about #quantumerrorcorrection - in the current era where qubit counts are a bottleneck in the systems available, adopting full-blown QEC can be a step backwards in terms of computational capacity. This is because even when it delivers net benefits in error reduction, QEC consumes a lot of qubits to do so and we just don't have enough right now... So how do we maximize value for end users while still pushing hard on the underpinning QEC technology? To answer this the team at Q-CTRL set out to determine new ways to significantly reduce the overhead penalties of QEC while delivering big benefits! In this latest demonstration we show that we can adopt parts of QEC -- indirect stabilizer measurements on ancilla qubits -- to deliver large performance gains without the painful overhead of logical encoding. And by combining error detection with deterministic error suppression we can really improve efficiency of the process, requiring only about 10% overhead in ancillae and maintaining a very low discard rate of executions with errors identified! Using this approach we've set a new record for the largest demonstrated entangled state at 75 qubits on an IBM quantum computer (validated by MQC) and also demonstrated a totally new way to teleport gates across large distances (where all-to-all connectivity isn't possible). The results outperform all previously published approaches and highlight the fact that our journey in dealing with errors in quantum computers is continuous. Of course it isn't a panacea and in the long term as we try to tackle even more complex algorithms we believe logical encoding will become an important part of our toolbox. But that's the point - logical QEC is just one tool and we have many to work with! At Q-CTRL we never lose sight of the fact that our objective is to deliver maximum capability to QC end users. This work on deploying QEC primitives is a core part of how we're making quantum technology useful, right now. https://lnkd.in/gkG3W7eE

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

PASSING FRAGILE QUANTUM STATES BETWEEN SEPARATE PHOTON SOURCES OR TRUE QUANTUM TELEPORTATION? Quantum communication aims to enable secure transmission of information across large distances by exploiting the principles of quantum mechanics. A central protocol in this context is quantum teleportation, which allows the transfer of quantum states without requiring the physical transport of the particles themselves. The essence of this process lies in maintaining quantum coherence—the stable phase relationships among superposed states—which ensures that the delicate correlations defining the quantum information are preserved during transmission. When photons originate from distinct sources, the challenge becomes even more formidable: the quantum states must remain indistinguishable and their superposition structures intact, so that interference and entanglement can be reliably established. Without coherence, the fragile quantum information encoded in superposition collapses into classical noise, undermining the fidelity of teleportation. Thus, overcoming issues of indistinguishability and coherence is not simply a technical detail but the fundamental requirement for faithfully transferring quantum states between separate photon sources. Recent experimental work using semiconductor quantum dots (QDs) has addressed this challenge. Researchers demonstrated photonic quantum teleportation between photons emitted by two separate GaAs quantum dots. In this scheme, one QD acted as a single-photon source, while the other generated entangled photon pairs. The single photon was prepared in conjugate polarization states and interfaced with the biexciton emission of the entangled pair through a polarization-selective Bell state measurement. This process enabled the polarization state of the single photon to be teleported onto the exciton emission of the entangled pair. A significant technical obstacle was the frequency mismatch between the two photon sources. This was mitigated using polarization-preserving quantum frequency converters, which aligned the photons to telecommunication wavelengths. The experiment achieved remote two-photon interference with a visibility of 30(1)% and a post-selected teleportation fidelity of 0.721(33), exceeding the classical limit. These results indicate that quantum coherence and superposition were preserved across distinct sources, consistent with successful teleportation. Unlike classical communication, quantum protocols provide intrinsic security, as attempts to intercept signals introduce detectable disturbances. Thus, while challenges remain in scaling and improving fidelity, this work shows that quantum teleportation between distinct photon sources is not merely state transfer but genuine teleportation, marking a step toward practical quantum communication networks. # https://lnkd.in/eBN4PTeC