Researchers Achieve 99.915% Fidelity In Qubit Control Via Light

Scaling up superconducting quantum computers has been limited by increasing numbers of signal cables within dilution refrigerators due to space constraints and heat build-up. Full control of superconducting qubits is now achieved using optically transmitted signals instead of traditional coaxial cables. A new method controls quantum bits, known as qubits, with light in place of metal cabling inside dilution refrigerators. These specialised cooling systems are essential for maintaining ultra-low temperatures required for superconductivity but become increasingly congested with wiring as qubit numbers rise.

Transmitting microwave signals via laser beams and converting them to electrical current using photodiodes inside the refrigerator circumvents space limitations and reduces heat build-up. The University of Science and Technology of China team has fully controlled superconducting qubits using light rather than conventional wiring within dilution refrigerators, which maintain temperatures colder than those achievable with conventional refrigeration. Dilution refrigerators are key for superconductivity, yet face increasing congestion as quantum computers scale up because each qubit traditionally requires a dedicated signal cable.