Amplifiers are crucial in every experiment carrying out a very sensitive measurement. However, they always degrade the information by adding noise. Quantum mechanics puts a limit on how small this degradation can be. Theoretically, the minimum noise energy added by a phase preserving amplifier to the signal it processes amounts at least to half a photon at the signal frequency. In this article, we show that we can build a practical microwave device that fulfills the minimal requirements to reach the quantum limit. This is of importance for the readout of solid state qubits, and more generally, for the measurement of very weak signals in various areas of science. We also discuss how this device can be the basic building block for a variety of practical applications such as amplification, noiseless frequency conversion, dynamic cooling and production of entangled signal pairs.
Probing Synthetic Caroli-de Gennes-Matricon States Through Critical Current in Full-Shell Nanowire Josephson Junctions
Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC(马德里材料科学研究所,西班牙高等科学研究委员会);Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid(马德里自治大学凝聚态物理系);Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid(马德里自治大学凝聚态物理中心);Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen(哥本哈根大学尼尔斯·玻尔研究所量子设备中心);Quantum Advanced Research Center (QuARC), CSIC(西班牙高等科学研究委员会量子高级研究中心)
Josephson-like magnetic tunnel junction -- transition from classical to quantum regime
Moscow Center for Advanced Studies(莫斯科高等研究中心);New Spintronic Technologies(新自旋电子技术公司);Prokhorov General Physics Institute of the Russian Academy of Sciences(俄罗斯科学院普罗霍罗夫普通物理研究所)
We demonstrate an Al superconducting quantum interference device in which the Josephson junctions are implemented through gate-controlled proximitized Cu mesoscopic weak-links. The latter behave analogously to genuine superconducting metals in terms of the response to electrostatic gating, and provide a good performance in terms of current-modulation visibility. We show that, through the application of a static gate voltage, we are able to modify the interferometer current-flux relation in a fashion which seems compatible with the introduction of $π$-channels within the gated weak-link. Our re…