A Collaborative Research Breakthrough

A joint research effort by the University of Sydney and IBM has identified some of the primary factors leading to errors during calculations in quantum computers. Researchers have discovered a way to significantly reduce error rates, paving the way for improvements in the reliability of these devices.

New Insights on Enhancing Quantum Computer Reliability

The operation of quantum computers is based on the ability to place devices (whether they are superconducting circuits, ions, photons, Rydberg atoms, or others) in a quantum state and maintain them in that state. However, the natural tendency is to interact with the surrounding environment, leading to unintended changes in the quantum state and, consequently, calculation errors.

Researchers from the University of Sydney and IBM have announced a new study, published in Nature Communications, where they successfully identified one of the main sources of error during calculations.

To ensure that errors do not occur, quantum computers perform measurements at the halfway point of each circuit (i.e., of each function). In this way, some qubits are “read,” causing their quantum state to collapse into a classical state, allowing verification of whether errors have occurred. However, this procedure halts calculations and keeps the computer in a stalled state. According to the research, a significant portion of errors occurs precisely during this phase.

“This procedure occurs very, very often at each step of quantum computation. Each of these halfway circuit measurements takes time, and the rest of the operation must remain inactive while the measurement is completed. It’s one of the main obstacles,” said Professor Stephen Bartlett from the Nano Institute at the University of Sydney.

“But we cannot bypass this step; it’s an essential part of quantum error correction. What we did in this study was to quantitatively ascertain what kind of performance we need with these error checks. This is vital for designing systems that can scale and operate.”

Researchers utilized an IBM Quantum Eagle r2 computer with 156 qubits to measure the impact of these pauses during qubit measurement and found that reducing their duration leads to a significant increase in the survival of logical qubits during each measurement cycle: from less than 90% to 96%. They also confirmed that the noise from measurements is one of the main causes of errors in today’s devices.

“Quantum error correction is essential for building large-scale quantum computers, but it introduces a range of very complex engineering challenges,” stated Robin Harper from the Department of Physics and the Nano Institute at the University of Sydney.

“We wanted to identify which physical processes limit performance on today’s quantum devices. What we discovered is that the act of measuring qubits during a computation can itself create instabilities. By redesigning how measurements are made, we can significantly improve the reliability of logical qubits.”

The outcome of this research indicates that it will be possible to reduce the error levels of quantum computers, which will ultimately enhance their reliability and, consequently, their computing power. The findings once again highlight that there are still many elements to optimize in the design of quantum computers, and that merely increasing the number of qubits will not lead to improved performance; conversely, it is interesting to note how every aspect of these devices is quantum: ultimately, the study reaffirms how observation influences systems, albeit in an unexpected manner.