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Séminaire QUEST

Jeudi 1er septembre à 9h30,
Salle Rémy Lemaire,K223

Orateur : F. Lecocq (NIST, Boulder)
"Measuring nothing, perfectly : the ideal quantum measurement of microwave photons"


Many superconducting quantum circuits rely on microwave photons to measure or couple quantum systems, such as superconducting qubits or micro-mechanical resonators. The ability to noiselessly route and amplify microwave fields is crucial to the observation of truly quantum behavior, and find applications in quantum computing, quantum feedback, position measurements, etc. However, to date, there is no system able to achieve an ideal quantum non demolition measurement of such microwave fields. Indeed, parametric amplifiers, while quantum limited, reflect the amplified signal and back-act onto the system under test, requiring a circulator to break reciprocity (i.e the symmetry of the scattering parameters under exchange of source and detector). Unfortunately, circulators are ultimately incompatible with microwave quantum circuits due to size, loss and magnetic field.

In this talk I will describe the development of a new generation of quantum limited, non-reciprocal microwave amplifiers [1,2]. Using microwave drives, the experimentalist turns on a set of parametric interactions between the modes of a microwave resonant circuit, allowing one to choose in-situ between different modes of operation : frequency conversion, circulation or any combination of reciprocal/non-reciprocal and phase sensitive/preserving amplification. With low insertion loss (<0.5dB), high return loss (<-15dB), high directivity (<-15dB) and high gain (>18dB), these devices are a new tool for quantum measurements.

[1] L. Ranzani and J. Aumentado, New J. Phys. 17, 023024 (2015)
[2] K. M. Sliwa, et al, Phys. Rev. X 5, 041020 (2015)

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