A near–quantum-limited Josephson traveling-wave parametric amplifier

Chris Macklin(Lawrence Berkeley National Laboratory), Kevin P. O’Brien(University of California, Berkeley), David Hover(MIT Lincoln Laboratory), Mollie E. Schwartz(University of California, Berkeley), Vladimir Bolkhovsky(MIT Lincoln Laboratory), Xiang Zhang(Lawrence Berkeley National Laboratory), William D. Oliver(MIT Lincoln Laboratory), Irfan Siddiqi(University of California, Berkeley)
Science
September 4, 2015
10.1126/science.aaa8525
Cited by 799

Abstract

Detecting single-photon level signals—carriers of both classical and quantum information—is particularly challenging for low-energy microwave frequency excitations. Here we introduce a superconducting amplifier based on a Josephson junction transmission line. Unlike current standing-wave parametric amplifiers, this traveling wave architecture robustly achieves high gain over a bandwidth of several gigahertz with sufficient dynamic range to read out 20 superconducting qubits. To achieve this performance, we introduce a subwavelength resonant phase-matching technique that enables the creation of nonlinear microwave devices with unique dispersion relations. We benchmark the amplifier with weak measurements, obtaining a high quantum efficiency of 75% (70% including noise added by amplifiers following the Josephson amplifier). With a flexible design based on compact lumped elements, this Josephson amplifier has broad applicability to microwave metrology and quantum optics.

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