Qubits filter for better superposition lifetime

Schematic of a Josephson quantum filter (JQF).

Researchers at the Tokyo Medical and Dental University (TMDU), RIKEN, and the University of Tokyo propose an improved method for isolating the qubits in a quantum computer from the external environment, which may help usher in the era of practical quantum computing.

There is a fundamental tradeoff between the lifetime of the qubit superpositions and the processing speed. This is because the qubits must be carefully shielded from interacting with the environment, or the fragile superposition will snap back to being just a one or zero in a process called decoherence. To delay this loss of quantum fidelity, qubits in quantum computers are coupled only weakly to the control line through which the qubit control pulses are applied. Unfortunately, such a weak coupling limits the speed that computations can be run.

The team theoretically showed how coupling a second filter qubit to the control line can greatly reduce the noise and spontaneous radiative losses that lead to decoherence. This allows the connections to be strong, which lends itself to faster cycle times.

The paper has been published in Physical Review Applied. (TMDU)

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