Taming the Void: Chinese Scientists Control Quantum Chaos in a Major Leap Forward

In a landmark experiment, scientists from the Institute of Physics at the Chinese Academy of Sciences (CAS) have successfully observed and controlled a critical intermediate stage of quantum decoherence. Using the 78-qubit superconducting quantum processor, Chaung-tzu 2.0, the team managed to tame quantum chaos, extending the life of quantum information and marking a significant step toward building more reliable and powerful quantum computers. This achievement provides a crucial window of opportunity to manipulate quantum data before it’s lost to environmental noise, a primary obstacle in the field.

The Enemy of Quantum Computing: Decoherence

Quantum computers derive their immense potential from the delicate states of qubits, which can exist in multiple states at once (superposition) and be linked together (entanglement). However, these states are incredibly fragile. Decoherence is the process where a quantum system loses its information to the surrounding environment, essentially decaying into a classical, chaotic state. This loss of information is the single biggest challenge preventing the construction of large-scale, fault-tolerant quantum computers. Modeling the dynamics of this decay for systems with dozens of qubits is impossible for even the most powerful classical supercomputers, which is why the CAS team used the Chaung-tzu 2.0 processor itself as a direct quantum simulator.

A Plateau of Stability

The researchers focused on a temporary, stable state that occurs just before a quantum system fully descends into chaos, a phenomenon known as prethermalization. During this phase, the system surprisingly resists the pull of chaos and preserves its information, creating a stable “plateau.” Professor Fan Heng, one of the lead scientists, compared this to ice melting: for a period, despite continuous heating, the temperature of the ice-water mixture remains stable at zero degrees. “On the Chaung-tzu 2.0, we clearly saw that during this plateau, chaos is suppressed,” Fan noted.

Crucially, the team demonstrated that this plateau is controllable. By applying specially designed control sequences of microwave pulses, they could actively lengthen or shorten the duration of this stable phase. This ability to manage the prethermalization state effectively acts as a shield, creating a controllable window to perform computations before the system decoheres.

Implications for the Future of Quantum Computing

This breakthrough has profound implications for the quantum industry. The ability to control the prethermalization plateau opens new avenues for developing advanced error-correction schemes. By extending the coherence time-the duration for which a qubit can hold information-scientists can perform more complex and meaningful calculations. This experiment is a powerful demonstration of using quantum computers to solve problems that are intractable for classical machines, showcasing a practical quantum advantage.

The work on Chaung-tzu 2.0 places it among the leading global efforts in quantum computing, a field with intense competition from companies like Google, IBM, and other Chinese research groups working on processors like Zuchongzhi 3.0. While the race to build a fully fault-tolerant quantum computer is far from over, the ability to observe and manipulate the very process of quantum chaos is a critical and inspiring leap forward. The team plans to develop larger and more flexible quantum chips to explore even more complex quantum behaviors.