Efficient polarization squeezing in optical fibers

Abstract

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 λ/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.c 2018 Optical Society of America OCIS codes: 190.3270, 190.4370, 270.5290, 270.6570. The budding field of quantum information holds promise to revolutionize communication. In particular the field of quantum information with continuous variables has received much attention in the last decades with the realization, for instance, of quantum teleportation, quantum cryptography and dense coding.1 Most of these protocols require the use of squeezed (or entangled) states of light that are generally detected using a strong local oscillator, which makes the scalability of quantum networks difficult. Recently, polarization squeezing has attracted much attention 2-6 as it can be measured in direct detection, 7 making it especially attractive for cryptography and other quantum communication applications. Furthermore the flucuations of the polarization variables can be mapped onto the collective fluctuations of an atomic ensemble, paving the way to quantum memory.8 To date polarization squeezing has been achieved using the nonlinear interactions in Optical Parametric Amplifiers, 4 optical fibers 5 and atomic media. 6In this paper we present the results of a novel and efficient method of bright pulse polarization squeezing generation using the Kerr effect in an optical fiber. This setup is greatly simplified relative to other schemes and leads to high squeezing levels. Further, this method enables us to completely characterize all quadratures of the state exiting an optical fiber. In particular we measured the angle by which the squeezed uncertainty region has been rotated by the nonlinear Kerr effect.It has been known for a long time that the optical Kerr effect in glass fiber can generate quadrature squeezing. This third order nonlinear effect (χ 3 ), also refered to as Self Phase Modulation produces an intensity dependent change in the refractive index. The squeezing generation can be understood by a single mode picture represented in Fig. 1(a): since different amplitudes experience different rotations in phase space, the fluctuation circle (corresponding to shot noise) of the input field is transformed into an ellipse. The squeezed quadrature is rotated by the angle θ sq relative the amplitude quadrature. Since the Kerr effect conserves photon number, the amplitude fluctuations remain at the shot noise level preventing direct detection of the squeezing.Polarization squeezing overcomes this problem. It can be generated by overlapping two quadrature squeezed beams produced in the two orthogonal polarization modes of the fiber, visualized byâ x andâ y in Fig. 1(b). This setup, seen in Fig. 2, is similar to our previous experiment producing polariza...

Quantum Reconstruction of an Intense Polarization Squeezed Optical State

“…The quantum states on which we performed the measurements were polarization squeezed states created by the Kerr nonlinearity experienced by ultrashort laser pulses in optical fibers [15]. Our experiment employs a Cr 4 :YAG laser emitting near Fourier-limited 140 fs FWHM pulses at 1497 nm with a repetition rate of 163 MHz.…”

Coherent optical control of correlation waves of spins in semiconductors

“…Such light ͑polarization-squeezed vacuum͒ was discussed by Karrasiov, 24 Lehner et al, 25 and Korolkova et al 26 and generated in several experiments. 27,28 In this paper we demonstrate ͓see Eq. ͑29͔͒ that by externally manipulating the phase of the frequency dependent photonic correlations a possibility opens up of optical coherent control of spins in semiconductors.…”

“…It is an intriguing direction for future research, especially since strong correlated light sources are becoming increasingly available. 27,28 Another interesting direction to explore is related to effects of nonclassical squeezed light ͉M͉ Ͼ N on the spectrum, which we showed to have a unique effect on the static spin correlations. 29 Although unexplored in this work, light in the quantum optical regime may have a unique effect on the temporal spin fluctuations.…”

“…These photon correlations are spectral functions, which can be externally controlled at the source. [26][27][28] Given these functions it is possible to characterize the fluctuations of the Stokes vector, whose average is assumed to be zero in this calculation ͑unpolarized͒. 29 We note that there is also a ͗S z ͑q , t͒ ͑1͒ S z ͑qЈ , tЈ͒ ͑3͒ ͘ contribution which we discuss in detail in Appendix C. This contribution has a much smaller phase space compared to ͗S z ͑q , t͒ ͑2͒ S z ͑qЈ , tЈ͒ ͑2͒ ͘ and therefore we neglect it.…”

One-dimensional Bose gas dynamics: Breather relaxation

“…These quantum predictions use a truncated Wigner approximation, which is a 1/N expansion, in a regime where other exactly known predictions are recovered to high accuracy. Such dynamical calculations are testable in forthcoming BEC experiments.Techniques for observing near lossless quantum dynamics have led to quantitative tests of quantum field dynamics in photonic systems [1][2][3][4]. Improvements in ultra-cold quantum gas experiments mean that these experiments can now also compare first principles calculations of many-body quantum dynamics with observations [5].…”