We report on a novel and efficient source of polarization squeezing using a single pass through an optical fiber. Simply passing this Kerr squeezed beam through a carefully aligned lambda/2 waveplate and splitting it on a polarization beam splitter, we find polarization squeezing of up to 5.1 +/- 0.3 dB. The experimental setup allows for the direct measurement of the squeezing angle.
In this work, we investigate three different compact fibered systems generating vacuum squeezing that involve optical cavities limited by the end surface of a fiber and by a curved mirror and containing a thin parametric crystal. These systems have the advantage to couple squeezed states directly to a fiber, allowing the user to benefit from the flexibility of fibers in the use of squeezing. Three types of fibers are investigated: standard single-mode fibers, photonic-crystal large mode area single-mode fibers and short multi-mode fiber taped to a single-mode fiber. The observed squeezing is m…
We study polarization squeezing of a light beam initially in the coherent state using the nonlinear interaction hamiltonian $ H=k\big(\hat a_{x}^{\dagger2}+{\hat a_{x}}^2\big)$. For the degree of polarization squeezing, we use a definition written in the final form by the authors and also used in earlier papers. We find that the polarization squeezing can be very high and the degree of polarization squeezing can be less than unity by a very small amount. We achieve the polarization squeezing even for very low beam intensity under some conditions involving phase angles in the polarization modes…
Polarization squeezing is shown to occur in non-degenerate parametric amplification of coherent light and the degree of squeezing at interaction time $T$ can be as large as $1-e^{-2T}$. This gives $86.4\%$ polarization squeezing for $T=1$ and $98.2\%$ for $T=2$. One simple case when this occurs is on taking initially plane polarized light having equal amplitudes in the two modes that finally has equal intensities of two circular polarizations. This suggest the experimental settings of parameters to achieve this extent of polarization squeezing in coherent light.
A 2.8-dB polarization squeezing of the Stokes operator S2 for the rubidium D1 line (795 nm) is achieved, with the lowest squeezing band at an audio frequency of 2.6 kHz. Two methods are applied for improving the squeezing towards low frequencies: an orthogonal-polarized locking beam that precludes residual unwanted interference and quantum noise locking method that stabilizes the relative phase between the squeezed vacuum and the local oscillator. The squeezing level is limited by absorption-induced losses at short wavelengths, here is 397.5 nm. The generated polarization squeezed light can be…
We analyze a fiber-optic gyroscope design enhanced by the injection of quantum-optical squeezed vacuum into a fiber-based Sagnac interferometer. In the presence of fiber loss, we compute the maximum attainable enhancement over a classical, laser-driven fiber-optic gyroscope in terms of the angular velocity estimate variance from a homodyne measurement. We find a constant enhancement factor that depends on the degree of squeezing introduced into the system but has diminishing returns beyond $10$--$15$ dB of squeezing. Under a realistic constraint of fixed total fiber length, we show that segmen…
We report on nonlinear squeezing effects of polarization states of light by harnessing the intrinsic correlations from a polarization-entangled light source and click-counting measurements. Nonlinear Stokes operators are obtained from harnessing the click-counting theory in combination with angular-momentum-type algebras. To quantify quantum effects, theoretical bounds are derived for second- and higher-order moments of nonlinear Stokes operators. The experimental validation of our concept is rendered possible by developing an efficient source, using a spectrally decorrelated type-II phase-mat…
We study polarization squeezing of a pure photon number state which is obviously polarized but the mere change in the basis of polarization leads to simultaneous polarization squeezing in all the components of Stokes operator vector except those falling along or perpendicular to the direction of polarization state, is observed. We use the most general definition of polarization squeezing and discuss the experimental feasibility of the result. We also observe that a squeezing operation like non-degenerate parametric amplification of the state does not reveal simultaneous squeezing in all Stokes…
We have developed an optical parametric amplification module for quadrature squeezing with input and output ports coupled with optical fibers for both fundamental and second harmonic. The module consists of a periodically poled LiNbO${}_{3}$ ridge waveguide fabricated with dry etching, dichroic beamsplitters, lenses and four optical fiber pigtales. The high durability of the waveguide and the good separation of squeezed light from a pump beam by the dichroic beamsplitter enable us to inject intense continuous-wave pump light with the power of over 300 mW. We perform $-$4.0${\pm}$0.1 dB of nois…
Optical spin squeezing: bright beams as high-flux entangled photon sources
与Wang和Sanders [Physical Review A 68，012101（2003）]的自旋压缩不等式类似，我们发现了描述宏观偏振相关的不等式，这些不等式为所有经典场所遵守，其违反意味着构成光束的光子的纠缠。我们考虑了一个现实的和精确可解的实验方案，采用偏振压缩光从光学参量振荡器（OPO），发现任何两个光子分离小于OPO相干时间是偏振纠缠。偏振纠缠对损耗是鲁棒的，并且非常明亮：效率可以超过现有的“超亮”对源至少一个数量级。这种将自旋压缩不等式转换到光域的方法，将使压缩-纠缠关系的直接检验成为可能。
Squeezing measurement with spectrally broadened in microstructured fiber local oscillator
Russian Quantum Center（俄罗斯量子中心）；Moscow Institute of Physics and Technology（莫斯科物理技术学院）；M.V.Lomonosov Moscow State University（莫斯科国立大学）；Dianov Fiber Optics Research Center（季阿诺夫光纤研究中心）
Squeezed light is one of the resources of photonic quantum technology. Among the various nonlinear interactions capable of generating squeezing, the optical Kerr effect is particularly easy-to-use. A popular venue is to generate polarization squeezing, which is a special self-referencing variant of two-mode squeezing. To date, polarization squeezing generation setups have been very sensitive to fluctuations of external factors and have required careful tuning. In this work, we report on a development of a new all-fibre setup for polarization squeezing generation. The setup consists of passive …
在Hermann A. Haus提出的双向非线性光脉冲传输问题的一般量子理论，并应用于研究光纤光栅孤子的量子特性。发现光纤光栅孤子通过光栅后会自动受到振幅压缩，并且在一定长度后压缩比达到饱和。最佳压缩比出现在脉冲能量略高于基孤子能量时。只要孤子的演化是周期性的，利用切趾光栅还可以同时压缩孤子脉冲宽度和增强压缩。
Entanglement and squeezing in a two-mode system: theory and experiment
本文报道了在光学谐振腔中，线偏振光束与冷铯原子云相互作用产生不可分离光束。我们将两个线性偏振模式的压缩转换为正交纠缠，并展示了如何使用连续变量的不可分离性准则来找出双模系统中产生的最佳纠缠[Duan et al.，物理修订信函84，2722（2000）]。我们验证了这种方法的实验与直接测量的不可分性，使用两个零差检测。然后将这种纠缠映射到一个偏振基上，实现了偏振纠缠。
We report the experimental demonstration of polarization squeezed beam at 795 nm by combining a quadrature squeezed beam with a coherent beam. The quadrature squeezed beam is generated by a degenerate optical parametric amplifier based on a PPKTP crystal. Stokes parameter squeezing of -3.8 dB and anti squeezing of +5.0 dB is observed. This polarization squeezed beam resonant to rubidium D1 line has potential applications in quantum information networks and precise measurement beyond the shot noise limit.
Squeezed light, which is easily degraded by loss, could benefit from generation directly in optical fiber. Furthermore, highly nonlinear fiber could offer more efficient generation with lower pump power and shorter fiber lengths than standard single-mode fiber. We investigate non-polarization-maintaining highly nonlinear fiber (HNLF) for squeezed-light generation by characterizing possible sources of excess noise, including its zero-dispersion wavelength (ZDW) variation and polarization noise. We find significant ZDW variation and excess polarization noise. We believe the polarization noise is…
Bright squeezed light can be generated in optical fibers utilizing the Kerr effect for ultrashort laser pulses. However, pulse propagation in a fiber is subject to nonconservative effects that deteriorate the squeezing. Here, we analyze two-mode polarization squeezing, which is SU(2)-invariant, robust against technical perturbations, and can be generated in a polarization-maintaining fiber. We perform a rigorous numerical optimization of the process and the pulse parameters using our advanced model of quantum pulse evolution in the fiber that includes various nonconservative effects and real f…
