TY - JOUR
T1 - Beyond the standard quantum limit for parametric amplification of broadband signals
AU - Renger, M.
AU - Pogorzalek, S.
AU - Chen, Q.
AU - Nojiri, Y.
AU - Inomata, K.
AU - Nakamura, Y.
AU - Partanen, M.
AU - Marx, A.
AU - Gross, R.
AU - Deppe, F.
AU - Fedorov, K. G.
N1 - Publisher Copyright:
© 2021, The Author(s).
PY - 2021/12
Y1 - 2021/12
N2 - The low-noise amplification of weak microwave signals is crucial for countless protocols in quantum information processing. Quantum mechanics sets an ultimate lower limit of half a photon to the added input noise for phase-preserving amplification of narrowband signals, also known as the standard quantum limit (SQL). This limit, which is equivalent to a maximum quantum efficiency of 0.5, can be overcome by employing nondegenerate parametric amplification of broadband signals. We show that, in principle, a maximum quantum efficiency of unity can be reached. Experimentally, we find a quantum efficiency of 0.69 ± 0.02, well beyond the SQL, by employing a flux-driven Josephson parametric amplifier and broadband thermal signals. We expect that our results allow for fundamental improvements in the detection of ultraweak microwave signals.
AB - The low-noise amplification of weak microwave signals is crucial for countless protocols in quantum information processing. Quantum mechanics sets an ultimate lower limit of half a photon to the added input noise for phase-preserving amplification of narrowband signals, also known as the standard quantum limit (SQL). This limit, which is equivalent to a maximum quantum efficiency of 0.5, can be overcome by employing nondegenerate parametric amplification of broadband signals. We show that, in principle, a maximum quantum efficiency of unity can be reached. Experimentally, we find a quantum efficiency of 0.69 ± 0.02, well beyond the SQL, by employing a flux-driven Josephson parametric amplifier and broadband thermal signals. We expect that our results allow for fundamental improvements in the detection of ultraweak microwave signals.
UR - http://www.scopus.com/inward/record.url?scp=85118633063&partnerID=8YFLogxK
U2 - 10.1038/s41534-021-00495-y
DO - 10.1038/s41534-021-00495-y
M3 - Article
AN - SCOPUS:85118633063
SN - 2056-6387
VL - 7
JO - npj Quantum Information
JF - npj Quantum Information
IS - 1
M1 - 160
ER -