IBM researchers have demonstrated a multi-channel quantum interconnect, linking two 120-qubit chips with four superconducting couplers that transfer quantum information at an average accuracy of 99 percent, and up to 99.29 percent at their best.
The work concerns the long-distance couplers, or L-couplers, that connect qubits, the core units of quantum computers. Unlike conventional bits, which are restricted to a binary state of 1 or 0, qubits can also exist in a superposition of states until they are measured, offering an exponential increase in computing power.
Scaling up quantum computers by linking separate chips with L-couplers makes more practical sense than packing ever more qubits onto the same microchip, the team argues. But the connectors need to carry fragile quantum information over long distances in quantum terms, in this case 80 centimeters. The researchers linked two 120-qubit chips with four L-couplers made of superconducting aluminum.
The team observed that the cables lost very little energy in use, stayed operational through three cycles of warming up and cooling down, and could also transmit entanglement between the two chips. "To our knowledge this is the first demonstration of a multi-channel quantum interconnect between large-qubit superconducting processors," they write in their paper.
The couplers are intended to be installed inside fridge-like cryogenic systems that IBM unveiled in August, which keep qubits at temperatures about 180 times colder than deep space. The company's aim is to link hundreds of quantum chips inside these units and deliver a fault-tolerant quantum computer by 2029.
"The successful connection and operation of these cryogenic modules signals a leap forward in that direction," says Jay Gambetta, director of IBM Research, who was not directly involved in the study.
There is work remaining before the couplers are ready for use. The researchers noted magnetic interference that affected signal quality, and further efficiency improvements will be required. The research has yet to be peer-reviewed; a preprint is available on arXiv.
Analysis
Why This Matters
- Scaling up quantum computers is one of the field's biggest hurdles; linking separate chips with couplers is a more practical route than packing more qubits onto a single microchip.
- The 99 percent average transfer accuracy across four channels is, the researchers say, the first demonstration of its kind between large-qubit superconducting processors.
- The couplers are designed for IBM's cryogenic modules, part of the company's stated plan to deliver a fault-tolerant quantum computer by 2029.
Background
Unlike classical bits, which are restricted to a binary state of 1 or 0, qubits can occupy a superposition of states until measured, offering an exponential increase in computing power. Adding ever more qubits to a single chip becomes impractical, so IBM is pursuing a modular approach: linking chips with long-distance couplers capable of carrying fragile quantum states over distances of 80 centimeters inside systems cooled to temperatures far colder than deep space.
What to Watch
- Whether the magnetic interference that affected signal quality can be reduced in future iterations.
- Peer review of the preprint, which has yet to be assessed.
- Further efficiency improvements needed before the couplers are operational, and progress toward connecting hundreds of chips ahead of the 2029 target.
Checked
12 claims in this story checked against 1 source: 11 supported.
Show each claim
- SupportedIBM linked two 120-qubit chips with four L-couplers.ScienceAlert: “Here, the researchers linked two 120-qubit chips together with four L-couplers made of superconducting aluminum”
- SupportedThe interconnect achieved an average transfer accuracy of 99 percent.ScienceAlert: “achieving an average transfer accuracy of 99 percent, and peaking at 99.29 percent.”
- SupportedThe best transfer accuracy was 99.29 percent.ScienceAlert: “achieving an average transfer accuracy of 99 percent, and peaking at 99.29 percent.”
- SupportedThe multi-channel interconnect is a step toward modular, scalable quantum computers.ScienceAlert: “These four high-fidelity L-couplers establish a practical path to scalable quantum interconnects for modular quantum computing,”
- SupportedThe researchers call this the first demonstration of a multi-channel quantum interconnect between large-qubit superconducting processors.ScienceAlert: “To our knowledge this is the first demonstration of a multi-channel quantum interconnect between large-qubit superconducting processors, and it establishes the combined L-coupler technology presented here as a viable building block for scaling modular systems,”
- Partly supportedThe researchers argue that linking chips makes more practical sense than packing more qubits onto one chip.ScienceAlert: “Scaling up quantum computers by linking multiple chips with L-couplers makes more practical sense than trying to pack ever more qubits together on the same microchip.”
- SupportedThe couplers carry quantum information over a distance of 80 centimeters.ScienceAlert: “But the connectors need to be capable of carrying fragile quantum information over very long distances in quantum terms – 80 centimeters (31.5 inches) long in this case.”
- SupportedThe cables remained operational through three warming and cooling cycles.ScienceAlert: “The team also observed that their cables lost very little energy in use, stayed operational through three cycles of warming up and cooling down, and could also transmit entanglement between the two chips.”
- SupportedThe cables could transmit entanglement between the two chips.ScienceAlert: “The team also observed that their cables lost very little energy in use, stayed operational through three cycles of warming up and cooling down, and could also transmit entanglement between the two chips.”
- SupportedJay Gambetta said the modules’ successful connection and operation signals a leap forward, and he was not directly involved in the study.ScienceAlert: ““The successful connection and operation of these cryogenic modules signals a leap forward in that direction and will accelerate our progress alongside continued innovation in quantum hardware, software, and algorithms,” says Jay Gambetta, director of IBM Research, who wasn't directly involved in the study.”
- SupportedIBM aims to link hundreds of quantum chips and deliver a fault-tolerant quantum computer by 2029.ScienceAlert: “The ultimate aim is to link hundreds of quantum chips together in these cryogenic units – cooled down to temperatures 180 times colder than deep space – and from there to deliver the world's first fault-tolerant quantum computer by 2029.”
- SupportedThe research has not yet been peer-reviewed and a preprint is available on arXiv.ScienceAlert: “The research has yet to be peer-reviewed, but a preprint is available on arXiv .”
