Amplification of squeezed states

Y. Yamamoto, Susumu Machida, Shōgo Saito +2 more

Lowell S. Brown

The relation of a previous paper on the parametric amplification of a quantum oscillator to squeezed states is described. In particular, we show that in general the amplification factor is also the ``squeezing factor'' of the final state.

Kevin Zelaya, Sanjib Dey, Véronique Hussin

John Alfio Vaccaro

In this thesis we examine linear amplification of squeezed light, the phase properties of squeezed light and the effect on the phase of light from linear amplification. Previous studies of linear amplifiers of light have shown that (i) when amplifying squeezed light the power gain must be less than 2 to preserve some squeezing in the output light; and (ii) a squeezed output cannot be generated from a non-squeezed input. However, these studies were restricted to a class of linear amplifier that can now be identified as not being squeezed. In this thesis we show how to breach the gain limit with a squeezed linear amplifier, and how to generate squeezed light using a squeezed linear attenuator.

P. L. Knight, Vladimír Bužek

Shaojie Li, Jiachen Liu, Changchang Zhang +4 more

Quantum noise fundamentally limits the performance of fiber-optic systems beyond the standard quantum limit (SQL), restricting long-distance quantum key distribution, quantum communication, and precision quantum sensing. To overcome these limitations, quantum-squeezed states enable quadrature-dependent noise suppression, yet their benefits rapidly degrade under fiber attenuation, necessitating low-noise amplification. Since conventional phase-insensitive amplifiers (PIAs) impose a minimum 3 dB noise figure (NF) penalty and disrupt quantum correlations, phase-sensitive amplification (PSA) becomes essential. In this work, we propose a PSA based on dual-pump frequency-degenerate four-wave mixing (FWM) to amplify weak coherent squeezed states. Here, the PSA is seeded by an information-carrying single-mode squeezed state, where the information is encoded in the displacement degree of freedom, rather than in the squeezing itself. By optimizing the relative phases among the squeezed state, pump fields, and weak signal, the scheme maintains proper squeezing alignment and preserves the encoded quantum correlations during propagation. Under low-loss conditions, it is shown that the effective NF reaches −7.787 dB, demonstrating that the scheme enables quantum-limited amplification suitable for long-haul transmission and offering a viable path toward scalable fiber-based quantum technologies.