TY - JOUR
T1 - Microwave Measurement beyond the Quantum Limit with a Nonreciprocal Amplifier
AU - Lecocq, F.
AU - Ranzani, L.
AU - Peterson, G. A.
AU - Cicak, K.
AU - Metelmann, A.
AU - Kotler, S.
AU - Simmonds, R. W.
AU - Teufel, J. D.
AU - Aumentado, J.
N1 - Publisher Copyright:
© 2020 American Physical Society. © 2020 American Physical Society. US.
PY - 2020/4
Y1 - 2020/4
N2 - The measurement of a quantum system is often performed by encoding its state in a single observable of a light field. The measurement efficiency of this observable can be reduced by loss or excess noise on the way to the detector. Even a quantum-limited detector that simultaneously measures a second noncommuting observable would double the output noise, therefore limiting the efficiency to 50%. At microwave frequencies, an ideal measurement efficiency can be achieved by noiselessly amplifying the information-carrying quadrature of the light field but this has remained an experimental challenge. Indeed, while state-of-the-art Josephson-junction-based parametric amplifiers can perform an ideal single-quadrature measurement, they require lossy ferrite circulators in the signal path, drastically decreasing the overall efficiency. In this paper, we present a nonreciprocal parametric amplifier that combines single-quadrature measurement and directionality without the use of strong external magnetic fields. We extract a measurement efficiency of 62-9+17% that exceeds the quantum limit and that is not limited by fundamental factors. The amplifier can be readily integrated with superconducting devices, creating a path for ideal measurements of quantum bits and mechanical oscillators.
AB - The measurement of a quantum system is often performed by encoding its state in a single observable of a light field. The measurement efficiency of this observable can be reduced by loss or excess noise on the way to the detector. Even a quantum-limited detector that simultaneously measures a second noncommuting observable would double the output noise, therefore limiting the efficiency to 50%. At microwave frequencies, an ideal measurement efficiency can be achieved by noiselessly amplifying the information-carrying quadrature of the light field but this has remained an experimental challenge. Indeed, while state-of-the-art Josephson-junction-based parametric amplifiers can perform an ideal single-quadrature measurement, they require lossy ferrite circulators in the signal path, drastically decreasing the overall efficiency. In this paper, we present a nonreciprocal parametric amplifier that combines single-quadrature measurement and directionality without the use of strong external magnetic fields. We extract a measurement efficiency of 62-9+17% that exceeds the quantum limit and that is not limited by fundamental factors. The amplifier can be readily integrated with superconducting devices, creating a path for ideal measurements of quantum bits and mechanical oscillators.
UR - http://www.scopus.com/inward/record.url?scp=85085120828&partnerID=8YFLogxK
U2 - 10.1103/PhysRevApplied.13.044005
DO - 10.1103/PhysRevApplied.13.044005
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AN - SCOPUS:85085120828
SN - 2331-7019
VL - 13
JO - Physical Review Applied
JF - Physical Review Applied
IS - 4
M1 - 044005
ER -