A qubit chain cuts logical qubit decay by half

Researchers from the University of Messina in Italy, Adam Mickiewicz University in Poland, Fuzhou University in China, and The University of Michigan, Ann Arbor, Michigan, USA have theoretically investigated a system to extend the coherence of quantum bits. The work investigates a chain of superconducting qubits arranged with alternating XX and YY ultrastrong interactions, utilizing the two lowest energy states as a single logical qubit. The authors demonstrate that increasing interaction strength or the number of qubits in the chain suppresses the logical qubit’s pure dephasing rate to zero, and reduces its relaxation rate to half that of a single physical qubit, demonstrating the feasibility of high-fidelity single and two-qubit gates. A logical qubit constructed from a chain of superconducting qubits can maintain coherence significantly longer than its constituent physical qubits, according…