In 2025, breakthroughs continued to emerge from laboratories around the world. From the miraculous “teleportation” between optical quantum chips to the interconnection of quantum nodes spanning tens of kilometers, these technologies are becoming a reality at an unprecedented pace.
Scientists have achieved the first-ever teleportation of quantum gates between chips, built a metropolitan-scale quantum network, and even converted the spins of 13,000 atoms into a “dark state” capable of storing information. These achievements signal the arrival of a new era of absolutely secure communications and disruptive growth in computing power. The prototype of the quantum internet is already quietly taking shape before our very eyes.
Chip-to-chip teleportation
Professor Ren Xifeng’s research group, part of Academician Guo Guangcan’s team at the University of Science and Technology of China, has successfully achieved quantum-controlled NOT gate teleportation between two optical quantum integrated chips. This is a key step in building large-scale quantum networks and a latest breakthrough that has garnered significant attention.
The research team fabricated a quantum entangled light source based on a silicon-based photonic chip and transmitted the photons to another chip via single-mode optical fiber. The team employed high-dimensional quantum encoding technology to significantly simplify the linear optical quantum operations required within a single node.
Experimental results show that at a 5-meter fiber interconnection distance, the gate-state fidelity reaches 95.69% and the logic gate process fidelity is 94.81%. Even when the interconnection fiber is extended to 1 kilometer, the gate-state fidelity remains as high as 94.07% and the logic gate process fidelity is 93.04%.
Ion-photon entanglement
By precisely controlling an electric field, scientists guide ions one by one into an optical cavity. Within the cavity, a calibrated laser pulse causes each ion to emit a single photon, whose polarization is entangled with the ion’s quantum state.
This process generates a stream of photons, each associated with a different ion qubit in the register. These photons can be transmitted to remote nodes and used to entangle different quantum devices.
The researchers achieved an average ion-photon entanglement fidelity of 92%, demonstrating the robustness of this approach. A key advantage of this technique lies in its scalability. Early experiments were limited to linking two to three ion qubits with a single photon.
The experimental setup in Innsbruck can now be expanded to much larger registers, potentially accommodating hundreds or even more ions, paving the way for connecting complete quantum processors across laboratories and even continents.
Dark state storage technology
A research team from the University of Cambridge and colleagues from the University of Linz successfully transformed 13,000 nuclear spins into collectively entangled states, known as “dark states.” These states enable quantum information to be written, stored, retrieved, and read out with high fidelity.
The researchers achieved a storage fidelity of nearly 69% and a coherence time exceeding 130 microseconds. Quantum dots, nanoscale structures with unique optical and electronic properties, have attracted widespread attention in quantum communications for their ability to emit single photons.
Building effective quantum networks requires stable quantum bits that can not only interact with photons but also locally store quantum information.
Quantum relay breakthrough
A quantum physics research team at the University of Innsbruck, Austria, has constructed a quantum repeater node for standard telecommunications wavelengths. This core component of the quantum repeater consists of two single-matter systems capable of generating entanglement and performing entanglement exchange operations at standard photon frequencies.
The repeater, which houses a source and storage of light-matter entanglement, generates entanglement in independent network links. These links are connected via entanglement exchange, ultimately distributing the entanglement over long distances.
The newly constructed repeater node consists of two calcium ions trapped in an ion trap within an optical resonator. The scientists demonstrated quantum information transmission over a 50-kilometer optical fiber, with the quantum repeater positioned midway between the source and destination.
The researchers also calculated the electronic and control improvements required to enable transmission over 800 kilometers, which would enable connections between cities as far apart as Innsbruck and Vienna.
Multi-directional transmission system
MIT researchers have developed a new device that enables multivector quantum information transmission between processors using photons. Traditional superconducting processors rely on point-to-point connections, which can lead to latency and error accumulation as the number of modules increases.
An MIT research team used superconducting waves to guide photons, enabling each processor to emit and absorb particles in user-defined directions. This engineering innovation addresses a key challenge in interconnecting quantum modules. In their study, the scientists connected two modules, each containing four qubits.
The qubits act as an interface, converting information into photons that travel along a waveguide. By controlling the phase of microwave pulses, photons are emitted in the desired direction, and the pulses are reversed in time for absorption by particles in a remote module. Using a reinforcement learning algorithm to pre-calibrate the photons, absorption efficiency increased to 60%, demonstrating the possibility of stable remote entanglement.
This technology enables entanglement between physically disconnected qubits, laying the foundation for parallel operations in scalable networks.
Phase control network
For applications such as distributed quantum computing, it is necessary to connect various quantum information processing nodes through wide-area quantum teleportation. The primary challenge in establishing entanglement between independent quantum memories separated by long distances lies in controlling the phase of single photons.
Entanglement schemes based on single-photon interference offer advantages in terms of entanglement rate, but are extremely challenging to implement experimentally. During the entanglement process, subtle phase fluctuations introduced by the control lasers, frequency-converted pump lasers, and long fiber channels in the quantum memory can lead to entanglement decoherence.
The team designed and developed a sophisticated phase control scheme that suppresses and controls the laser linewidth through ultrastable cavity frequency stabilization, establishes phase correlation between the read and write lasers through an optical phase-locked loop, and establishes phase correlation between two nodes through remote time-sharing phase comparison.
Using these phase control techniques and quantum frequency conversion, the team achieved entanglement between quantum memories separated by more than ten kilometers. This foundation enabled them to construct the world’s first metropolitan three-node quantum entanglement network, which can establish entanglement between any two quantum memory nodes.
