Amplification and squeezing of quantum noise with a tunable Josephson metamaterial

Abstract

An array of 488 Josephson junctions that amplifies and squeezes noise beyond conventional quantum limits should prove useful in the study and development of superconducting qubits and other quantum devices. It has recently become possible to encode the quantum state of superconducting qubits and the position of nanomechanical oscillators into the states of microwave fields1,2. However, to make an ideal measurement of the state of a qubit, or to detect the position of a mechanical oscillator with quantum-limited sensitivity, requires an amplifier that adds no noise. If an amplifier adds less than half a quantum of noise, it can also squeeze the quantum noise of the electromagnetic vacuum. Highly squeezed states of the vacuum can be used to generate entanglement or to realize back-action-evading measurements of position3,4. Here we introduce a general-purpose parametric device, which operates in a frequency band between 4 and 8 GHz. It adds less than half a noise quantum, it amplifies quantum noise above the added noise of commercial amplifiers and it squeezes quantum fluctuations by 10 dB.

Cite this article

Castellanos-Beltran, M., Irwin, K., Hilton, G. et al. Amplification and squeezing of quantum noise with a tunable Josephson metamaterial. Nature Phys 4, 929–931 (2008). https://doi.org/10.1038/nphys1090

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