MIT’s proposed qubit gives fragile memory an arm
A superconducting design divides storage and interaction between two coupled modes, with faster gates predicted in simulations.
MIT’s Great Dome, photographed on October 15, 2011. Campus context for the arm-qubit research; this is not a photograph of the proposed device. Image credit“Great Dome, Massachusetts Institute of Technology, Cambridge MA.jpg” — John Phelan, CC BY 3.0, via Wikimedia Commons. · https://creativecommons.org/licenses/by/3.0/
A has two awkwardly competing jobs: hold on to fragile information and interact quickly with the rest of a machine. MIT researchers propose giving it an arm. Their design, described by MIT on September 3, separates storage from connection so one job need not undermine the other.
One mode stores quantum information; a second acts as the arm that connects to other circuit elements. A device called a quarton coupler links the two. Its strong nonlinear interaction is designed to avoid the unwanted mixing that can accompany tightly connected quantum circuits.
The paper, published in Physical Review Applied on September 2, reports a simulated entangling gate lasting 17 nanoseconds, with gate infidelity of 0.0087% after including decoherence. Those are modeled results under the study’s assumptions, rather than measurements from an operating processor.
The practical attraction is the combination. needs qubits that retain information, gates that finish quickly and measurements that return answers promptly. Optimizing storage and interaction separately could give designers more room to improve all three together. The next decisive step is experimental: fabricate the architecture and test whether its predicted behavior survives real materials, fabrication variation and control imperfections. Until then, the arm qubit offers a concrete design to test, with a demanding set of performance targets.