Noiseless non-reciprocity in a parametric active device

Non-reciprocal devices such as circulators and isolators belong to an important class of microwave components employed in applications including the measurement of mesoscopic circuits at cryogenic temperatures 1-5 . The measurement protocols usually involve an amplification chain that relies on circulators to separate input and output channels and to suppress backaction from different stages on the sample under test. In these devices the usual reciprocal symmetry of circuits is broken by the phenomenon of Faraday rotation based on magnetic materials and fields 6 . However, magnets are averse to on-chip integration, and magnetic fields are deleterious to delicate superconducting devices 7,8 . Here we present a new proposal that combines two stages of parametric modulation to emulate the action of a circulator. It is devoid of magnetic components and suitable for on-chip integration. As the design is free of any dissipative elements and based on reversible operation, the device operates noiselessly, giving it an important advantage over other non-reciprocal active devices for quantum information processing applications. © 2011 Macmillan Publishers Limited. All rights reserved.