Google Willow Quantum Chip: Advancing Quantum Error Correction

Introduction

Google"s Willow quantum chip has made significant advancements in quantum error correction, addressing a long-standing challenge in the field of quantum computing. Here are the specific improvements:

Exponential Error Reduction

Willow demonstrates the ability to reduce errors exponentially as the system scales up using more qubits. As the size of logical qubit arrays increased from 3x3 to 5x5 to 7x7, the error rate was cut in half each time.

Below Threshold Performance

Willow achieved "below threshold" performance, meaning it can drive errors down while scaling up the number of qubits. This is a historic accomplishment that has been an outstanding challenge since quantum error correction was introduced in 1995.

Real-time Error Correction

Willow is one of the first examples of real-time error correction on a superconducting quantum system. This is crucial for useful computation, as errors need to be corrected fast enough to prevent ruining the computation.

Beyond Breakeven Demonstration

Willow"s arrays of qubits have longer lifetimes than individual physical qubits, indicating that error correction is improving the overall system.

Improved Qubit Performance

T1 times (relaxation time) have improved from 20 microseconds to 100 microseconds, a five-fold increase. Gate fidelity has improved by roughly a factor of two.

Logical Qubit Stability

Willow can keep a single logical qubit stable enough so errors occur maybe once every hour, a vast improvement over previous setups that failed every few seconds.

Error Suppression Factor

When creating various surface code arrays on the 105-qubit processor, the error rate was suppressed by a factor of 2.4 as additional qubits were added.

These advancements in quantum error correction with Willow represent a significant step towards building scalable, practical quantum computers and could potentially lead to breakthroughs in various fields such as drug discovery, optimization problems, and artificial intelligence.