Researchers from Rutgers University, IBM, and other institutions have demonstrated a quantum computer that can monitor and reset its own components while running, bringing the field closer to building machines that can correct their own errors. The study, published in Nature Physics, marks one of the largest demonstrations to date of real-time quantum feedback control.
Why this matters
This advance is important because quantum computers are extremely sensitive to disturbances. Heat, stray electromagnetic signals, and tiny hardware flaws can alter the quantum bits, or qubits, that store information. Without error correction, these disturbances accumulate until calculations become unreliable. A fault-tolerant quantum computer - one that keeps working correctly despite constant small errors in its individual qubits - has not yet been built, but this experiment shows that current hardware can perform the necessary checks and resets thousands of times across a large system.
The work also confirmed a theoretical prediction: when researchers increased how often they checked and reset qubits, the system underwent a phase transition-shifting abruptly from chaotic behavior to an orderly, controllable state. This demonstrated that order can emerge from disorder in quantum systems.
In the experiment, the team used a 156-qubit IBM Quantum Heron processor, selecting a connected chain of up to 100 qubits. They alternated between two tasks: one that scrambled information among neighboring qubits to create chaos, and another that checked and reset individual qubits to impose control. They performed nearly 5,000 operations linking pairs of qubits, along with nearly 5,000 checks and resets. When checking and resetting occurred more than half the time, the researchers could guide the system toward an orderly state.
Quantum computers use qubits, which - unlike ordinary computer bits that are either 0 or 1 - can exist in superposition, holding multiple possibilities at once until measured. This property gives quantum computers their power but makes error correction difficult: quantum information cannot be copied, and measuring it can destroy the state being used.
If fully realized, fault-tolerant quantum computers could solve problems beyond the reach of today's most powerful machines, such as designing better batteries, simulating complex molecules and materials, and running certain artificial intelligence applications.