De-Gaussification by inconclusive photon subtraction

压缩态光的蒸馏与纯化扩展分析

Extended analysis of distillation and purification of squeezed states of light

本文扩展分析压缩态光的蒸馏与纯化，提出光子减法结合弱相干位移的通用方案增强任意输入压缩度，还提出福克态滤波器克服损耗局限，且发现其与GKP态生成方法相关。

Teleportation improvement by inconclusive photon subtraction

Inconclusive photon subtraction (IPS) is a conditional measurement scheme to force nonlinear evolution of a given state. In IPS the input state is mixed with the vacuum in a beam splitter and then the reflected beam is revealed by ON/OFF photodetection. When the detector clicks we have the (inconclusive) photon subtracted state. We show that IPS on both channels of an entangled twin-beam of radiation improves the fidelity of coherent state teleportation if the energy of the incoming twin-beam is below a certain threshold, which depends on the beam splitter transmissivity and the quantum effici…

Squeezed Fock state by inconclusive photon subtraction

We analyze in details the properties of the conditional state recently obtained by J. Wenger, et al. [Phys. Rev. Lett. {\bf 92}, 153601 (2004)] by means of inconclusive photon subtraction (IPS) on a squeezed vacuum state $S(r)\ket{0}$. The IPS process can be characterized by two parameters: the IPS transmissivity $τ$ and the photodetection quantum efficiency $η$. We found that the conditional state approaches the squeezed Fock state $S(r)\ket{1}$ when $τ,η\to 1$, i.e., in the limit of single-photon subtraction. For non-unit IPS transmissivity and efficiency, the conditioned state remains close…

The role of the non-Gaussianity plays in the enhancement of the fidelity in continuous variable quantum teleportation

We investigated the role of non-Gaussianity (nG) plays in the enhancement of the fidelity in continuous-variable quantum teleportation of ideal Braunstein and Kimble (BK) protocol for coherent states, theoretically. The de-Gaussification procedure is realized through subtracting photons on the two-mode squeezed vacuum state (TMSVs). We find that the high fidelity always refers to a symmetrical arrangement of photon subtractions on the different modes of the TMSVs. The non-Gaussian resources demonstrate commendable superiorities compare with the Gaussian resources only for symmetrical arrangeme…

Multi-step two-copy distillation of squeezed states via two photon subtraction

Squeezed states of light have been improving the sensitivity of gravitational-wave observatories and are nonclassical resources of quantum cryptography and envisioned photonic quantum computers. The higher the squeeze factor is, the higher is the quantum advantage. Almost all applications of squeezed light require multi-path optical interference, whose unavoidable imperfections introduce optical loss, degrade the squeeze factor, as well as the quantum advantage. Here, for the first time, we experimentally demonstrate the distillation of Gaussian squeezed states that suffered from Gaussian phot…

Photon subtracted states and enhancement of nonlocality in the presence of noise

We address nonlocality of continuous variable systems in the presence of dissipation and noise. Three nonlocality tests have been considered, based on the measurement of displaced-parity, field-quadrature and pseudospin-operator, respectively. Nonlocality of twin beam has been investigated, as well as that of its non-Gaussian counterparts obtained by inconclusive subtraction of photons. Our results indicate that: i) nonlocality of twin beam is degraded but not destroyed by noise; ii) photon subtraction enhances nonlocality in the presence of noise, especially in the low-energy regime.