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Laser & Photonics Review

Experimental Preparation and Manipulation of Squeezed Cat States via an All‐Optical In‐Line Squeezer (Laser Photonics Rev. 16(12)/2022)

Meihong Wang, Miao Zhang, Zhongzhong Qin, Qiang Zhang, Li Zeng, Xiaolong Su, Changde Xie, Kunchi Peng

Published Dec 1, 2022• 1 citation
Publisher

Abstract

Optical Cat States In article number 2200336, Xiaolong Su and colleagues have developed an all-optical measurement-free in-line squeezer to prepare and manipulate optical squeezed cat states. The phase of the quadrature squeezing and squeezing parameter of the squeezed cat state are manipulated by changing the working condition of the in-line squeezer. The results provide a new method to prepare and manipulate optical squeezed cat states without losing their non-classicality.

DOI
10.1002/lpor.202270061

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Iterative CZC_ZCZ​-gate-based protocol for squeezed Schrödinger cat state engineering
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The origin of quantum noise is addressed and it can be eliminated when the quantum state is optimally prepared for the single measured observable. Minimum uncertainty states are reviewed using Q (α) -representation, which include squeezed states and number-phase minimum uncertainty states. Squeezing is a concept of trading quantum uncertainties between two conjugate observables to optimize the state for the measurement. Need for optical nonlinearity to achieve squeezing is induced. Principles and experimental results for squeezing quadrature amplitude and photon number are delineated. Applications to optical communications and optical precision measurement are briefly stated.
Multi-photon-added cat states are constructed by repeatedly applying the creation operator to a cat state. We study in detail their photon-number distribution, QQQ parameter, squeezing properties, and Wigner function. We show that photon addition induces a πππ phase shift in the original parity configuration whenever an odd number of photons is added, reflected as swapped vanishing probabilities and phase space displacements at the origin. Remarkably, the same process drives these states into a sub-Poissonian regime regardless of the relative phase between their coherent state components, making them valuable resources for quantum imaging, at the cost of losing quadrature squeezing, but gaining amplitude-squared one. We also discuss how these states can be generated using existing hardware.
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Non-Gaussian states, and specifically the paradigmatic cat state, are well known to be very sensitive to losses. When propagating through damping channels, these states quickly lose their nonclassical features and the associated negative oscillations of their Wigner function. However, by squeezing the superposition states, the decoherence process can be qualitatively changed and substantially slowed down. Here, as a first example, we experimentally observe the reduced decoherence of squeezed optical coherent-state superpositions through a lossy channel. To quantify the robustness of states, we introduce a combination of a decaying value and a rate of decay of the Wigner function negativity. This work, which uses squeezing as an ancillary Gaussian resource, opens new possibilities to protect and manipulate quantum superpositions in phase space.