Quantum computers, while rapidly advancing in size and potential, face a critical obstacle: errors. As these machines grow more powerful, the rate of errors threatens to render them impractical. Now, researchers have demonstrated a method to recycle and reuse qubits, improving their reliability and making complex computations more feasible.
The Error Problem in Quantum Computing
Existing quantum computers struggle with accuracy. They are too prone to errors for useful, real-world calculations that surpass traditional computers. While error-correction schemes are under development, a major challenge remains: creating enough high-quality qubits to run both the calculations and track those errors.
The standard approach divides qubits into two groups: those that manipulate data (the computational qubits) and those that monitor errors (ancilla qubits). Building enough of either type is difficult. A new strategy focuses on reducing the number of ancilla qubits needed by reusing them repeatedly.
Atom Computing’s Recycling Method
Researchers at Atom Computing have shown ancilla qubits can be recycled up to 41 times in a row. This is crucial because complex computations require many error-correction rounds, meaning a constant supply of fresh qubits would otherwise be needed. The team, led by Matt Norcia, achieved this with ytterbium atoms cooled to near absolute zero using lasers and electromagnetic pulses.
They organized their quantum computer into three zones:
- Computation Zone: 128 qubits run the calculations.
- Error-Tracking Zone: 80 qubits measure and replace erroneous qubits.
- Storage Zone: 75 qubits are held in a ready state for reuse.
This setup allows the team to reset ancilla qubits or swap them out with fresh ones as needed.
Challenges and Precision Control
The success of this method depends on extreme precision. Stray light from lasers can disrupt qubit function, so the researchers developed fine-tuned laser control and adjusted data qubit states to resist unwanted interference. This level of control is vital because without it, even modest calculations would require millions or billions of qubits – an impossible demand for current hardware.
Wider Implications for Quantum Progress
The ability to reuse qubits is not limited to Atom Computing. Yuval Boger of QuEra emphasizes that this capability is fundamentally important for quantum computing progress. Other researchers, including those at Harvard and MIT, have used similar methods with rubidium atoms to maintain quantum computations for hours. Even ion-based quantum computers, like Quantinuum’s Helios machine, can reuse qubits.
“Ancilla reuse is no longer just a desirable feature; it’s becoming a necessity for scaling quantum computing,” says Norcia.
This breakthrough represents a critical step towards building practical and reliable quantum computers capable of solving problems beyond the reach of classical machines.
