Quantum Chaos in Slow Motion: UCAS Achieves Prethermal Plateau in 78-Qubit Processor for Superior Data Processing

Breakthrough in Quantum Chaos Control Using Chuang-tzu 2.0 Processor

Chinese researchers from the University of Chinese Academy of Sciences (UCAS) and the Institute of Physics at the Chinese Academy of Sciences (CAS) have made a groundbreaking achievement by observing a tunable prethermal plateau on their 78-qubit superconducting quantum processor, Chuang-tzu 2.0. This discovery effectively puts quantum chaos in slow motion, allowing for prolonged stability in quantum states crucial for advanced data processing.

The experiment demonstrates how random multipolar driving (RMD) can suppress rapid heating in driven quantum systems, creating a stable prethermal regime that lasts over 1,000 driving cycles. This stability is vital for practical quantum computing, where maintaining coherence amid chaotic dynamics is a major hurdle.

Understanding Prethermal Plateau and Quantum Chaos

In quantum many-body systems, chaos leads to rapid thermalization, where the system heats up to an infinite-temperature state, scrambling quantum information. A prethermal plateau is a transient phase where heating is delayed, preserving useful quantum correlations longer. Traditional periodic drives (Floquet engineering) achieve this exponentially with frequency, but random drives typically cause fast heating.

Researchers introduced RMD, using structured random sequences with multipolar temporal correlations (order n). This slows chaos by engineering the drive's frequency spectrum, suppressing low-frequency components that drive heating. The prethermal lifetime scales algebraically as τ ~ (1/T)^{2n+1}, doubly tunable by frequency T and multipolar order n.

• Higher n enhances suppression through anti-aligned operators.
• Observed via particle imbalance and entanglement entropy metrics.

Chuang-tzu 2.0: A Marvel of Superconducting Quantum Engineering at UCAS

Chuang-tzu 2.0 is a flip-chip superconducting processor with 78 transmon qubits arranged in a 6×13 square lattice, coupled by 137 tunable couplers. Qubits have anharmonicity η ≈ -2π × 200 MHz, hopping J ≈ 2 MHz, simulating a 2D hard-core Bose-Hubbard model. Coherence times average T1 = 26.4 μs, enabling experiments over thousands of cycles with drive periods T = 3-8 ns.

Developed collaboratively by UCAS School of Physical Sciences and CAS Institute of Physics, this processor exemplifies China's investment in university-led quantum hardware. UCAS, as a graduate powerhouse, trains the next generation of quantum experts, integrating education with cutting-edge research.Explore research positions in quantum computing.

Step-by-Step Experimental Methodology

1. Initialization: Prepare density-wave state (every even row occupied).
2. Driving: Apply RMD sequences of U± operators over cycles.
3. Measurement: Track imbalance I = |N_even - N_odd| / (N_even + N_odd) and entropy S on subsystems via quantum-state tomography (QST).
4. Analysis: Fit lifetimes τ_I and τ_S, confirm power-law scaling.

For n=2 RMD on full 78 qubits, plateau persists ~100-500 cycles, with entanglement crossing from area-law (prethermal) to volume-law (thermalized).

Photo by MARIOLA GROBELSKA on Unsplash

Key Results: Tunable Stability and Scaling Laws

Results show clear plateaus: entropy S plateaus before avalanche to volume-law growth, imbalance I decays slowly then sharply. Lifetime τ grows with frequency (τ ∝ T^{-α}, α≈5 for n=2) and n. QST reveals non-uniform entanglement, challenging ETH assumptions in driven systems.

This 'slow motion' of chaos—delayed ergodicity—exceeds classical tensor-network limits, proving quantum advantage in simulating driven dynamics.

UCAS and CAS: Pillars of China's Quantum Higher Education

UCAS, with its School of Physical Sciences, affiliates many authors like Zheng-He Liu and Kai Xu, fostering PhD training in quantum tech. CAS labs provide hardware, but university programs drive innovation. This builds on USTC's Zuchongzhi successes, positioning Chinese universities as global leaders.Higher ed opportunities in China.

China's national strategy invests billions in quantum, with UCAS/USTC grads filling research jobs. The breakthrough highlights interdisciplinary higher ed.

Implications for Better Quantum Data Processing

Prethermal plateaus enable stable quantum information processing under drives, key for algorithms in noisy environments. Tunable stability supports fault-tolerant computing, error suppression, and simulating complex materials for drug discovery or optimization—revolutionizing data-heavy tasks.Read the Nature paper.

In China, this accelerates NISQ-era applications in finance, logistics.

Global Context and Chinese University Leadership

While IBM/Google push 100+ qubits, China's focus on control (e.g., USTC's 105-qubit Zuchongzhi 3.0) excels in dynamics. UCAS/CAS outpaces in driven-system studies, per Leiden rankings where Chinese unis top impact.Chinese universities lead research rankings.

Comparisons: Floquet prethermal exponential; RMD algebraic but versatile for non-periodic needs.

Photo by Yusuf Onuk on Unsplash

Challenges, Future Outlook, and Career Opportunities

Challenges: Scaling beyond 78 qubits, decoherence. Future: Hybrid drives for DTCS, topological phases; integrate with error correction.

For students, UCAS offers PhDs; jobs abound in quantum.Academic CV tips. University jobs in China booming.

Optimistic: Paves fault-tolerant quantum data processing by 2030s.

Stakeholder Perspectives and Broader Impacts

Lead author Kai Xu (UCAS): "Doubly tunable prethermal opens new paradigms." Experts hail simulation advantage.

Impacts: Boosts China's quantum talent pipeline, attracts global collaborators. Ethical AI-quantum fusion ahead.