Quantum-state engineering with Josephson-junction devices

TLDR

Quantum computing has spurred activity in using Josephson junction systems, where charge or phase degrees of freedom serve as qubits that can be coherently manipulated with voltage and current pulses, enabling logic gates within coherence times limited by circuit fluctuations. The paper reviews recent theoretical and experimental progress in quantum state engineering with Josephson junction devices. The authors analyze in detail the quantum measurement process using single‑electron transistors, SQUIDs, and other nanoelectronic devices.

Abstract

We review recent theoretical and experimental progress in quantum state engineering with Josephson junction devices. The concepts of quantum computing have stimulated an increased activity in the field. Either charges or phases (fluxes) of the Josephson systems can be used as quantum degrees of freedom, and their quantum state can be manipulated coherently by voltage and current pulses. They thus can serve as qubits, and quantum logic gates can be performed. Their phase coherence time, which is limited, e.g., by the electromagnetic fluctuations in the control circuit, is long enough to allow a series of these manipulations. The quantum measurement process performed by a single-electron transistor, a SQUID, or further nanoelectronic devices is analyzed in detail.