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Free keywords:
Quantum Physics, quant-ph
Abstract:
Entanglement drives nearly all proposed quantum information technologies. The
suppression of the uncertainty in joint quadrature measurements below the level
of vacuum fluctuations is a signature of non-classical correlations. Entangling
frequency modes of optical fields has attracted increased attention in recent
years, as a quantum network would rely on interfacing light at
telecommunication wavelengths with matter-based quantum memories that are
addressable at visible wavelengths. By up-converting part of a 1550 nm squeezed
vacuum state to 532 nm, we demonstrate the generation and complete
characterization of strong continuous-variable entanglement between widely
separated frequencies. Non-classical correlations were observed in joint
quadrature measurements of the 1550 nm and 532 nm fields, showing a maximum
noise suppression 5.5 dB below vacuum. A spectrum was measured to demonstrate
over 3 dB noise suppression up to 20 MHzmeasurement frequency. Our versatile
technique combines strong non-classical correlations, large bandwidth and, in
principle, the ability to entangle the telecommunication wavelength of 1550 nm
with any optical wavelength, making this approach highly relevant to emerging
proposals for quantum communication and computing.
