title: Josephson directional amplifier for quantum measurement of superconducting circuits.
abstract: We realize a microwave quantum-limited amplifier that is directional and can therefore function without the front circulator needed in many quantum measurements. The amplification takes place in only one direction between the input and output ports. Directionality is achieved by multipump parametric amplification combined with wave interference. We have verified the device noise performances by using it to read out a superconducting qubit and observed quantum jumps. With an improved version of this device, the qubit and preamplifer could be integrated on the same chip.
authors.affiliation: Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: Baleegh
authors.initials: B
authors.lastname: Abdo
authors.affiliation: Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: Katrina
authors.initials: K
authors.lastname: Sliwa
authors.affiliation: Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: S
authors.initials: S
authors.lastname: Shankar
authors.affiliation: Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Hatridge
authors.affiliation: Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: Luigi
authors.initials: L
authors.lastname: Frunzio
authors.affiliation: Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Schoelkopf
authors.affiliation: Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: Michel
authors.initials: M
authors.lastname: Devoret