Enhanced energy relaxation process of quantum memory coupled with a superconducting qubit

TL;DR

This paper investigates energy relaxation in hybrid quantum systems combining superconducting qubits and long-coherence memory qubits, revealing a fundamental leakage issue caused by decoherence and proposing feasible solutions.

Contribution

It identifies a fundamental energy leakage problem in hybrid quantum systems and explains its origin as an anti quantum Zeno effect, offering potential mitigation strategies.

Findings

Energy leakage from memory to superconducting qubit due to decoherence.

The leakage is interpreted as an anti quantum Zeno effect.

Proposed solutions are feasible with current technology.

Abstract

For quantum information processing, each physical system has different advantage for the implementation and so hybrid systems to benefit from several systems would be able to provide a promising approach. One of the common hybrid approach is to combine a superconducting qubit as a controllable qubit and the other quantum system with a long coherence time as a memory qubit. The superconducting qubit allows us to have an excellent controllability of the quantum states and the memory qubit is capable of storing the information for a long time. By tuning the energy splitting between the superconducting qubit and the memory qubit, it is believed that one can realize a selective coupling between them. However, we have shown that this approach has a fundamental drawback concerning energy leakage from the memory qubit. The detuned superconducting qubit is usually affected by severe decoherence, and this causes an incoherent energy relaxation from the memory qubit to the superconducting qubit via the imperfect decoupling. We have also found that this energy transport can be interpreted as an appearance of anti quantum Zeno effect induced by the fluctuation in the superconducting qubit. We also discuss a possible solution to avoid such energy relaxation process, which is feasible with existing technology.