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Physical Review A

Zero to π continuously controllable cross-phase modulation in a Doppler-broadened N -type electromagnetically-induced-transparency medium

R. B. Li, Chengjie Zhu, L. Deng, E. W. Hagley

Published Oct 29, 2015• 6 citations
Publisher

Abstract

We demonstrate an observation of zero to $\ensuremath{\pi}$ continuously controllable cross-phase-modulation based on an $N$-type electromagnetically-induced-transparency scheme in a room-temperature $^{87}\mathrm{Rb}$ vapor. We theoretically and experimentally show that the signal field acquires a $\ensuremath{\pi}$ phase shift compared with the reference light in the presence of the phase-control field. Using the method of the optical Mach-Zehnder interferometer, we demonstrate that a zero to $\ensuremath{\pi}$ continuously controllable phase gate can be built by modulating the phase-control field. In addition, our theoretical calculation agrees well with the experimental observation, and the results presented in this work hold potential applications for the orthogonal polarization or vector gate in quantum information processing.

DOI
10.1103/physreva.92.043838

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We demonstrate a fast Kerr phase gate in a room-temperature 85Rb vapor using a Raman gain method where the probe wave travels “superluminally”. Continuously variable, zero to π radian nonlinear Kerr phase shifts of the probe wave relative to a reference wave have been observed at 333 K. We show rapid manipulation of digitally encoded probe waves using a digitally encoded phase-control light field, demonstrating the capability of the system in information science and telecommunication applications.
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We demonstrate a fast, all-optical polarization gate in a room-temperature atomic medium. Using a Polarization-Selective-Kerr-Phase-Shift (PSKPS) technique, we selectively write a π phase shift to one circularly-polarized component of a linearly-polarized input signal field. The output signal field maintains its original strength but acquires a 90° linear polarization rotation, demonstrating fast, high-fidelity, dynamically-controlled polarization gate operation. The intensity of the polarization-switching field used in this PKSPK-based polarization gate operation is only 2 mW/cm2, which would be equivalent to 0.5 nW of light power (λ = 800 nm) confined in a typical commercial photonic hollow-core fiber. This development opens a realm of possibilities for potential future extremely low light level telecommunication and information processing systems.