title: Ultimate on-chip quantum amplifier.
abstract: We report amplification of electromagnetic waves by a single artificial atom in open 1D space. Our three-level artificial atom--a superconducting quantum circuit--coupled to a transmission line presents an analog of a natural atom in open space. The system is the most fundamental quantum amplifier whose gain is limited by a spontaneous emission mechanism. The noise performance is determined by the quantum noise revealed in the spectrum of spontaneous emission, also characterized in our experiments.
authors.affiliation: NEC Nano Electronics Research Laboratories, Tsukuba, Ibaraki 305-8501, Japan.
authors.forename: O V
authors.initials: OV
authors.lastname: Astafiev
authors.forename: A A
authors.initials: AA
authors.lastname: Abdumalikov
authors.forename: A M
authors.initials: AM
authors.lastname: Zagoskin
authors.forename: Yu A
authors.initials: YA
authors.lastname: Pashkin
authors.forename: Y
authors.initials: Y
authors.lastname: Nakamura
authors.forename: J S
authors.initials: JS
authors.lastname: Tsai