Manipulating the Quantum State of an Electrical Circuit

TL;DR

This paper presents the design and operation of a superconducting circuit called 'quantronium' that acts as a controllable two-level quantum system, demonstrating high coherence suitable for quantum computing.

Contribution

The paper introduces a novel superconducting circuit capable of arbitrary quantum state manipulation and high-fidelity measurement, advancing solid-state quantum processor development.

Findings

Quantum coherence quality factor Qphi=25000

Arbitrary quantum state evolution demonstrated

Potential for solid-state quantum computing

Abstract

We have designed and operated a superconducting tunnel junction circuit that behaves as a two-level atom: the ``quantronium''. An arbitrary evolution of its quantum state can be programmed with a series of microwave pulses, and a projective measurement of the state can be performed by a pulsed readout sub-circuit. The measured quality factor of quantum coherence Qphi=25000 is sufficiently high that a solid-state quantum processor based on this type of circuit can be envisioned.