Faster technique for resetting quantum circuits proposed by RIKEN physicists

(Phys.org) Rebooting a quantum computer is a tricky process that can damage its parts, but now two RIKEN physicists have proposed a fast and controllable way to hit reset.
The potential power of quantum computers lies in their ability to process ‘qubits’ that can take a value of zero or one—or be some fuzzy mix of both simultaneously.
“However, to reuse the same circuit for multiple operations, you have to force the qubits back to zero fast,” says Jaw Shen Tsai, a quantum physicist at the RIKEN Center for Quantum Computing. But that is easier said than done.
One of the best current ways to hit reset for qubits built from tiny superconductors is to link the qubit to a photon—a particle of light—in a tiny device called a resonator.The trouble with this method is that permanent entanglement to a decaying photon rapidly degrades the qubit’s quality, so that it rapidly ceases to be useful for future operations. “It’s bad for the qubit, whose lifetime becomes short,” says Tsai.
Now, Tsai and his RIKEN colleague Teruaki Yoshioka have devised a simulation to help find a better way of resetting the qubit, without harming it.
Based on their calculations, the pair proposed building a resonator that can be controlled using an additional junction made by sandwiching a superconducting material with an insulator, a normal metal, another insulator and another superconductor.
The team is now testing this set-up, which is held at low temperatures using a dilution refrigerator, with promising results. “This device should be very useful if we can implement it in a quantum circuit,” Tsai says.