Dresden 2020 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 52: Superconducting Electronics: SQUIDs, Qubits, Circuit QED, Quantum Coherence and Quantum Information Systems 2 (joint session TT/HL)
TT 52.4: Talk
Thursday, March 19, 2020, 10:15–10:30, HSZ 03
Experimental violation of the standard quantum limit for parametric amplification of broadband signals — •K. Fedorov1,2, M. Renger1,2, S. Pogorzalek1,2, C. Scheuer1,2, Q. Chen1,2, Y. Nojiri1,2, M. Partanen1, A. Marx1, F. Deppe1,2,3, and R. Gross1,2,3 — 1Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany — 2Physik-Department, TU München, 85748 Garching, Germany — 3Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany
Phase-preserving amplification is a crucial part of many protocols in microwave quantum information processing, such as quantum teleportation, remote state preparation [1], or dispersive qubit readout. Josephson parametric amplifiers (JPAs) allow amplification close to the standard quantum limit (SQL), implying a fundamental bound of 50 % 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.
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).
[1] S. Pogorzalek et al., Nat. Commun. 10, 2604 (2019).