Quantum computers promise to solve problems far beyond the reach of classical machines, from simulating new materials to transforming AI.
But one key challenge stands in the way: speed.
To be reliable, quantum computers must perform calculations and error corrections before their fragile quantum bits, or qubits, lose coherence.
Now, MIT researchers have built a new superconducting circuit that could dramatically speed up this process.
At its heart lies an innovatively created element called the “quarton coupler,” facilitating an unprecedented degree of engagement between light and matter, essential for both reading and managing qubits.
This advancement has the potential to increase operation speeds by as much as tenfold, thereby significantly advancing fault-tolerant, practical quantum computing in the real world.
The study was spearheaded by PhD graduate Yufeng “Bright” Ye and supervised by senior author Kevin O’Brien.
A new coupler enables more powerful quantum interactions.
The quarton coupler builds on years of foundational work at MIT’s Research Laboratory of Electronics. Initially developed by Ye as part of a photon detector project to improve quantum information processing, the coupler quickly became a central focus of the lab due to its versatility.
This device is a superconducting circuit designed to produce extremely strong nonlinear interactions between particles of light (photons) and matter (qubits).
Nonlinear coupling is key to most quantum operations—it allows systems to behave in complex, non-additive ways that drive computation.
“Most of the useful interactions in quantum computing come from nonlinear coupling of light and matter. If you can get a more versatile range of different types of coupling, and increase the coupling strength, then you can essentially increase the processing speed of the quantum computer,” Ye explains.
Researchers can amplify its nonlinear effects by feeding more current into the quarton coupler, setting the stage for faster and more reliable quantum processing.
Unprecedented velocity in measuring qubit states
The primary limitation in quantum computing at present lies in the readout stage—the measurement of a qubit’s state without prematurely collapsing its quantum information.
The more intense the connection between a qubit and its readout resonator, the quicker and more precisely this measurement can be performed.
To evaluate their design, they decided to
MIT
The team developed a chip featuring two superconducting qubits linked via a quarton coupler.
A single qubit functioned as an artificial atom, holding quantum data, whereas the other operated as a resonator. The exchange of information was facilitated through microwave photons.
This configuration facilitated a light-matter interaction roughly tenfold more intense than what was previously shown, significantly speeding up the reading process.
“The interaction between these superconducting artificial atoms and the microwave light that routes the signal is basically how an entire superconducting quantum computer is built,” Ye says.
Approaching fault-tolerant quantum systems
Swift operations and readings are essential since qubits possess a restricted coherence time—the period for which they maintain their quantum state.
Greater non-linear coupling enables a higher number of operations to be executed prior to qubit degradation, thereby facilitating additional cycles of error correction and enhancing computational accuracy.
“The more times you run the error correction process, the less error there will be in the outcomes,” according to Ye.
Besides achieving quicker light-matter coupling, the scientists also showcased robust matter-matter interactions among qubits, which is another key component for developing scalable quantum computing.
Each type of interaction is crucial for managing intricate processes.
quantum
algorithms on large machines.
The objective is to incorporate the quarton coupler into an expanded quantum framework that encompasses extra circuit elements such as filters, aiming to develop a fast and minimally error-prone reading mechanism.
“This project isn’t the final chapter. It showcases basic physics principles, however, the team is currently working on developing much faster data reading methods,” explains O’Brien.
The study was published in
Nature Communications
.