A theoretical shortcut could speed up certain operations on protected quantum states by more than a thousand times, giving disturbances less time to corrupt information.
Before quantum computers can help discover drugs or improve energy systems, they need to carry out calculations reliably. One promising approach, called bosonic quantum codes, stores information in states with built-in protection against certain errors. Preparing and controlling those states can be a slow process, giving disturbances more time to interfere with the information being protected.
Researchers at Chalmers University of Technology in Sweden have developed a theoretical method that could make some of those operations more than a thousand times faster. The speedup concerns the creation and control of protected quantum states, a task needed to make quantum computing more reliable.
“Our results address one of the major bottlenecks in the field: how to quickly and reliably create and control the error-correcting quantum states that could play an important role in future quantum computers,” says Lei Du, a researcher in Applied Quantum Physics at Chalmers and lead author of the study published in Physical Review Letters.
From thousands of cycles to one
The method builds on quantum lattice gates, a universal set of elementary quantum operations recently proposed by the same team. Researchers can combine these basic operations to perform more complex tasks involving bosonic states.
“You can think of it like building a large Lego castle. Instead of assembling it brick by brick and risking mistakes along the way, quantum lattice gates act like pre-built Lego modules that can be connected quickly and efficiently,” says Tangyou Huang, a researcher in Quantum Technology at Chalmers and co-author of the study.
The new method implements these gates through Floquet control, which steers a quantum system using repeating control signals. Each complete repetition is called a driving cycle.
“Our method shows that a diverse range of quantum operations on bosonic states can be completed within a single driving cycle, rather than the several thousand cycles that have been required previously. This makes the operations both faster and more efficient, while reducing the risk that disturbances will corrupt the information before the process is finished. It represents an important step towards fault-tolerant quantum computers,” says Lei Du.
Fault-tolerant computers can continue calculating reliably despite errors. That capability is needed for anticipated applications in cryptography, artificial intelligence, and logistics, as well as the drug discovery and energy research that quantum computers could eventually support.
Storing quantum information beyond individual qubits
Bosonic codes provide protection through the way they store information. They can use microwave or optical resonators, devices that sustain electromagnetic waves.
“Rather than storing quantum information in individual qubits, bosonic codes encode information in the microwave fields found within superconducting circuits. This approach has been shown to provide stronger protection against certain types of errors,” explains Tangyou Huang.
Potential sources of errors include electrical noise, cosmic radiation, and overheating. Conventional computers also encounter computational errors, but established techniques allow them to be detected and corrected quickly. Quantum error correction must contend with the sensitivity of the components holding the information.
“The fundamental building blocks of quantum computers, known as qubits, are so sensitive that even the smallest disturbance can cause the quantum state to deviate from the target, resulting in the loss of information. If too many errors accumulate before they can be corrected, the computation can fail,” says Lei Du.
Superconducting circuits offer a testing ground
The proposed method is particularly suited to superconducting quantum computers, one of the leading platforms being developed for large-scale quantum computing. Chalmers is using this technology to build a 100-qubit quantum computer. An experimental demonstration of the new control method is still pending.
“A key advantage of our approach is that it can be implemented using existing superconducting quantum circuit platforms. We are already discussing possible experimental realizations with colleagues at Chalmers, and we hope to see a demonstration of the method in the near future,” says Tangyou Huang.
Reference: “Single-Period Floquet Control of Bosonic Codes with Quantum Lattice Gates” by Tangyou Huang, Lei Du and Lingzhen Guo, 3 August 2026, Physical Review Letters.
DOI: 10.1103/tnb8-3m8m
The research was funded by the National Natural Science Foundation of China (NSFC), the Wallenberg Centre for Quantum Technology (WACQT), and the Knut and Alice Wallenberg Foundation.
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