---
title: "IBM Connects Two Nighthawk Quantum Processors: 99% Qubit Transmission Accuracy Paves the Way for Modular Supercomputers"
description: "IBM has successfully transferred quantum information between two Nighthawk processors with 99% accuracy, proving the viability of modular architecture. The company aims to build the Starling quantum supercomputer by 2029."
date: 2026-10-28T17:27:02.633Z
lang: en
url: https://xab.info/en/posts/ibm-nighthawk-quantum-processors-qubit-transfer-99
tags: [ibm, quantum-computing, nighthawk, qubits, starling, superconducting, modular-architecture]
author: "Roman V."
publisher: "XAB.info"
---

# IBM Connects Two Nighthawk Quantum Processors: 99% Qubit Transmission Accuracy Paves the Way for Modular Supercomputers

![IBM Quantum Nighthawk processor with 120 qubits being held by an engineer over a yellow board](https://xab.info/media/2026/10/28/ibm-kvantovye-protsessory-nighthawk-peredacha-kubitov-99/ibm-kvantovye-protsessory-nighthawk-peredacha-kubitov-99-1.webp)

## Key Points

- IBM demonstrated quantum information transfer between two Nighthawk processors with approximately 99% accuracy using four 80 cm coaxial cables
- The average fidelity of inter-chip CZ two-qubit operations was 94.75%, with a best result of 96.42%
- All four connections remained fully operational after three thermal heating and cooling cycles
- IBM plans to build the Starling modular quantum supercomputer by 2029

For the first time in the history of quantum computing, IBM engineers have demonstrated stable quantum information transfer between two independent processors with an accuracy of approximately 99%. The experiment, reported by 3DNews, marks a key milestone toward modular quantum computers—systems where multiple separate chips work as a single entity. Essentially, this brings the industry closer to creating quantum supercomputers capable of performing tasks beyond the reach of any single die.

### Two Nighthawks, Four Cables, 80 Centimeters

The experiment was based on two IBM Quantum Nighthawk superconducting processors, each containing 120 qubits. These chips were announced about a year prior to the reported test. To couple them, engineers used four 80 cm aluminum coaxial cables operating at microwave frequencies of around 5 GHz. Each cable formed a separate communication channel between specialized tunable qubits located at the ends of the connection. The cables were installed perpendicularly to the chip surfaces, and the contacts were secured using indium-indium pressure joints at room temperature. Notably, the assembly was performed after the processor modules had already been installed in the cryogenic system, significantly simplifying maintenance and scalability of the setup. Meanwhile, only a subset of qubits from each processor was connected and measured for the experiment, allowing for future expansion of active channels.

### Entanglement and Cross-Chip Two-Qubit Operations

Beyond simple quantum state transfer, the researchers demonstrated the joint execution of two-qubit operations and the creation of entangled states, including simultaneously across two adjacent channels. The average fidelity of inter-chip CZ operations—controlled-Z, a two-qubit quantum operation linking qubits on different dies—was 94.75%, with the best recorded result reaching 96.42%. These figures are slightly lower than state transfer fidelity because the operation itself involves several additional quantum transformations. Crucially, all four connections remained operational after three full thermal heating and cooling cycles without contact failure, confirming the mechanical and electrical reliability of the proposed architecture.

### L-coupler: Proven Connector Functionality

The experiment clearly showed that the L-couplers introduced alongside the Nighthawk processors are capable of linking independent quantum processors and transferring quantum information between them. This is not merely a laboratory curiosity, but proof that scaling quantum computers is technically feasible. The ability to integrate chips into modules opens the path to increased performance and fault tolerance in quantum computers, enabling more complex algorithms and efficient error correction codes that are critical for moving from demonstration experiments to practical computing.

### "Starling": The First Modular Quantum Supercomputer by 2029

IBM has already developed standard cryogenic racks for modular systems, and the company plans to use them to build the first practically viable modular quantum supercomputer, codenamed Starling. The successful experiment connecting two quantum processors confirmed that quantum data can be transmitted between adjacent racks and further down the chain. According to the company, IBM now has a clear roadmap to achieve its goal by 2029, in line with its previously announced quantum development plan.

### Industry Significance

IBM's achievement fits into the broader industry trend of transitioning from single chips to modular architectures. While the primary limitation of quantum computers was previously the number of qubits on a single die, the focus is now shifting to the quality of inter-chip links and long-distance entanglement stability. A transmission accuracy of around 99% and the retention of functionality after thermal cycles are the parameters without which no modular quantum computer can leave the research lab. The Nighthawk experiment demonstrates that the engineering foundation for this transition is already in place, and the remaining challenges are primarily systemic rather than fundamental.

## Fact-Check & Sources

- [Шаг к квантовым суперкомпьютерам: IBM научилась передавать квантовую информацию между чипами с точностью 99 % window-new](https://3dnews.ru/1150515/shag-k-kvantovim-superkompyuteram-ibm-nauchilas-peredavat-kvantovuyu-informatsiyu-megdu-chipami-s-tochnostyu-99-) - The primary source contains all key figures: 99% accuracy, 120 qubits per chip, four 80 cm cables, 5 GHz, CZ 94.75/96.42%, 3 thermal cycles, Starling target by 2029. There are no internal contradictions.

## FAQ

### What quantum information transmission accuracy was achieved in IBM's experiment?

The accuracy of quantum information transfer between two Nighthawk processors was approximately 99%. The average fidelity of inter-chip CZ two-qubit operations was 94.75%, with a peak result of 96.42%.

### How were the two Nighthawk processors connected?

The processors were connected using four 80 cm aluminum coaxial cables operating at microwave frequencies around 5 GHz. The cables were installed perpendicular to the chip surfaces, and contacts were secured with indium-indium pressure joints at room temperature.

### What is a modular quantum computer and why is it needed?

A modular quantum computer is a system composed of multiple separate chips working as a single setup. This approach bypasses the qubit limit on a single die, enhances fault tolerance, and enables more complex algorithms and error correction codes.

### When does IBM plan to release the Starling quantum supercomputer?

IBM aims to build the first modular Starling quantum supercomputer by 2029. The company has already developed standard cryogenic racks for such systems.

### How many qubits does each Nighthawk processor contain?

Each IBM Quantum Nighthawk processor contains 120 qubits. Two such processors were used in the experiment.