Experimental violation of the standard quantum limit for parametric amplification of broadband signals
ORAL
Abstract
Phase-preserving amplification of weak signals is a crucial part of many protocols in microwave quantum information processing, such as quantum teleportation, remote state preparation, or dispersive qubit readout. Flux-driven Josephson parametric amplifiers (JPAs) allow amplification close to the standard quantum limit (SQL), implying a fundamental bound of 1/2 for the maximal quantum efficiency η for amplification of narrowband input signals. We demonstrate that the SQL does not hold for broadband input signals and experimentally find η = 70% with an amplification chain consisting of a JPA and a cryogenic HEMT amplifier. We show that η can reach 100% and experimentally is limited by the Poissonian fluctuations in the JPA pump line. This result can be exploited for multiple applications such as high-efficiency parity measurements of superconducting qubits.
*We acknowledge support by Germany’s Excellence Strategy EXC-2111-390814868, Elite Network of Bavaria through the program ExQM, and the European Union via the Quantum Flagship project QMiCS (GrantNo.820505)
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Presenters
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Michael Renger
- Walther-Meißner-Institut & Technische Universtät München, Germany