Superconducting quantum circuits as a platform for studies of non-stationary cavity quantum electrodynamics

Superconducting circuits with Josephson junctions can behave quantum mechanically at ultralow temperatures and therefore they are used as building blocks for the construction of quantum computers and simulators. A remarkable... [ view full abstract ]

Superconducting circuits with Josephson junctions can behave quantum mechanically at ultralow temperatures and therefore they are used as building blocks for the construction of quantum computers and simulators. A remarkable feature of superconducting quantum circuits is their high tunability. This feature makes it possible to use them as a tool to study various effects of quantum electrodynamics in a cavity, which are hard to realize in other physical systems. We show that non-adiabatic modulation of effective coupling constant between qubits and a resonator can result in dynamic Lamb effect, when the qubit (artificial atom) is excited due to instanteneous change of its dressing by virtual photons. This effect can be significant in systems with artificial atoms due to the possibility of parametric periodical modulation of coupling constant with the optimal frequency. We further reveal a very rich dynamical behavior of such parametrically-driven hybrid systems. It includes various nontrivial dynamical regimes, enhancement of quantum effects in one of the subsystems by finite and optimal energy dissipation rate in another subsystem, as well as generation and storage of qubit-qubit entanglement in the intrinsically dissipative system. The key role in these effects is played by a fine balance between dissipation, Tavis-Cummings processes which exchange excitations between photon and qubit degrees of freedom, and anti-Tavis-Cummings processes which change the number of excitations in the system by two. The effects we study can be used in quantum technologies. They are also of importance for the full control of qubits-cavity coupled dystems.

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