Quantum computing promises a future where machines can solve problems so complex, they make today’s most advanced supercomputers seem like pocket calculators. From cracking encryption algorithms that safeguard our digital world to simulating molecular interactions for revolutionary drug discoveries, quantum computers hold the potential to transform society. But there’s a catch: building a truly powerful quantum computer isn’t as simple as adding more qubits or making the system bigger. Much like how classical computers rely on complex interconnects—CPUs talking to memory chips, GPUs, and storage devices—quantum computers need their components to work together seamlessly. And in the quantum world, this is no easy feat.
Imagine trying to hold a delicate conversation where every whisper must be perfectly clear, but the participants are miles apart, speaking through a telephone line that distorts every word. That’s the challenge quantum engineers face today. Current quantum architectures are based on what’s called “point-to-point” connections. These setups require quantum information—often carried by fragile particles of light called photons—to be transferred from one processor to another through a series of intermediary steps. Every handoff risks distorting the message, compounding errors along the way. It’s like playing a high-stakes game of quantum telephone.
But now, researchers at MIT have unveiled a groundbreaking solution: a scalable “all-to-all” interconnect architecture for superconducting quantum processors. Think of it as building a quantum superhighway where information can travel directly between any processors in a network—no more messy relay races or garbled messages. This advancement could be the key to scaling up quantum systems from today’s small-scale demonstrations to tomorrow’s world-changing machines.
Their work, published in Nature Physics, demonstrates how they created a network of quantum processors connected by a specialized superconducting waveguide. Using this new device, they sent photons—tiny packets of light that carry quantum information—between processors on demand. More importantly, they showed they could generate remote entanglement between qubits that weren’t physically connected. That’s a crucial milestone on the road to building distributed quantum computers.
But what exactly does all this mean? Let’s dive in.
Quantum Computers Need Better Highways
At its core, a quantum computer stores and processes information using quantum bits, or qubits. Unlike classical bits, which are either a 0 or 1, qubits can be in multiple states at once thanks to the principle of superposition. Entanglement, another quantum property, lets qubits share a deep connection so that the state of one instantly influences the state of another, no matter the distance between them. These phenomena give quantum computers their superpowers—but also make them extremely fragile.
Current superconducting quantum processors are often built in tightly-packed arrays. Local connections between neighboring qubits are relatively easy to establish. But what happens when you need to entangle qubits on opposite ends of a chip? Or worse, when you want to connect separate processors that are housed in different cryogenic packages? Traditional wiring and routing solutions just don’t cut it. You end up with a spaghetti mess of connections prone to interference, signal degradation, and, ultimately, error.
Today’s point-to-point networks are inefficient and error-prone, requiring photons to make multiple hops across nodes, with each hop increasing the likelihood of mistakes. This bottleneck limits how big and powerful quantum processors can grow.
MIT’s Quantum Interconnect: A Game-Changer
The MIT team, led by Aziza Almanakly, Beatriz Yankelevich, and senior author William D. Oliver, tackled this issue by developing a novel interconnect architecture that provides all-to-all connectivity. This means every quantum processor in the network can directly communicate with every other processor—no middlemen required.
The heart of their system is a superconducting waveguide—a special kind of wire that can shuttle photons between quantum processors over potentially long distances. Photons are perfect messengers for quantum information because they can travel quickly and aren’t easily disturbed by their surroundings (as long as those surroundings are meticulously controlled, like in a cryogenic environment).
What makes MIT’s interconnect special is its flexibility. The team designed the system to send photons at different frequencies, at different times, and in both directions along the waveguide. It’s like building a multi-lane quantum freeway where traffic flows smoothly in either direction, and you can choose which vehicle (or photon) goes where and when.
Even better, they demonstrated that multiple modules could be coupled to this waveguide. In principle, you could have a scalable network of processors, all connected by the same “quantum bus,” communicating freely and efficiently. This is a huge leap from today’s point-to-point models.
Quantum “Pitching and Catching”
One of the most fascinating aspects of the MIT system is how they send and receive photons between processors. Imagine a game of catch, but instead of tossing a ball, they’re throwing a quantum particle that must maintain its fragile quantum state throughout its journey.
The researchers built quantum computing modules, each equipped with four qubits that act as an interface with the waveguide. These interface qubits are responsible for “pitching” and “catching” photons. Using carefully timed microwave pulses, they can add energy to a qubit, causing it to emit a photon. By controlling the phase of these pulses, they can direct the photon to travel in a specific direction along the waveguide.
When it’s time to “catch” the photon, they reverse the pulses to guide it into a receiving qubit in a distant module. This careful control ensures that the photon arrives intact, with its quantum information preserved.
Remote Entanglement: Quantum’s Secret Weapon
Transferring photons is just the first step. The real magic happens when the researchers generate remote entanglement—a quantum link between qubits that aren’t physically connected.
Here’s where things get wild: to create entanglement, the researchers “half-launch” a photon from one qubit. Quantum mechanics being what it is, the photon is now in a superposition—it’s both retained by the sender and emitted toward the receiver. When the receiver absorbs its share of the photon, the two modules become entangled, even though they’re separated by space.
But ensuring the photon is absorbed efficiently on the receiving end is tricky. As the photon travels through the waveguide, it can be distorted by imperfections—like wire bonds or joints—that reduce absorption efficiency and introduce error. To overcome this, the team employed a reinforcement learning algorithm. This AI technique helped them predict how the photon would be distorted and allowed them to “pre-distort” its shape for optimal delivery. It’s like adjusting your pitch to compensate for wind, ensuring the ball lands perfectly in the catcher’s mitt.
The result? The team achieved a photon absorption efficiency greater than 60%—a significant milestone. This level of efficiency allowed them to demonstrate remote entanglement with enough fidelity to be useful in future quantum networks.
Toward a Quantum Internet
So why does this matter? Remote entanglement is a foundational building block for distributed quantum computing and even for what some call the “quantum internet.” By entangling distant qubits, you can perform quantum operations in parallel across different processors, vastly increasing the system’s computational power.
With MIT’s interconnect, you can, in principle, build networks where any processor can talk to any other, no matter where they are in the system. Want to entangle processors on opposite ends of your network? No problem. Need to move quantum data around dynamically, depending on the task at hand? That’s now possible.
“This means we can have multiple modules, all along the same bus, and we can create remote entanglement between any pair of our choosing,” explains Yankelevich. This flexibility opens the door to scalable, modular quantum computers—systems that can grow in power simply by adding more modules to the network.
What’s Next?
There’s still work to be done. The MIT team envisions improving the photon absorption efficiency even further by refining the physical path photons take—perhaps by integrating components in 3D structures rather than relying on a flat, 2D waveguide. They also aim to speed up their protocol to minimize errors introduced by the passage of time, an ever-present challenge in quantum systems.
“In principle, our remote entanglement generation protocol can also be expanded to other kinds of quantum computers and bigger quantum internet systems,” Almanakly says. Whether it’s superconducting qubits, trapped ions, or other quantum technologies, the fundamental ideas of scalable, flexible communication are universal.
The Big Picture
MIT’s new quantum interconnect isn’t just an incremental advance—it’s a bold reimagining of how quantum processors can work together in large, distributed systems. If today’s quantum computers are like isolated islands, this technology promises to build the bridges, highways, and fiber-optic cables that connect them into a unified, powerful continent.
As researchers around the world race toward the era of practical quantum computing, scalable, flexible communication between quantum processors is likely to be one of the defining challenges. Thanks to this breakthrough, we’re one big step closer to making that vision a reality.
Reference: Aziza Almanakly et al, Deterministic remote entanglement using a chiral quantum interconnect, Nature Physics (2025). On arXiv: DOI: 10.48550/arxiv.2408.05164