High bandwidth squeezed states of light

In Quantum key distribution (QKD) two-mode squeezed states of light can be utilized to encrypt data with absolute security. High transmission rates for the secret quantum key are achieved via large squeezing factors as well as a high squeezing bandwidth. While the first improves the measured bits per sample, the latter allows for a higher sample measuring rate per second. The generation of high bandwidth squeezed light with a strong non-classical noise suppression is implemented to address both topics.

The generation of high bandwidth squeezed light with a strong non-classical noise suppression is implemented to address both topics. As a first step, a highly efficient second harmonic generation cavity was set up to generate the necessary 775 nm pump power for the squeezing resonator [1]. We additionally measured the optical absorption of the nonlinear medium periodically poled potassium titanyl phosphate (PPKTP) for the squeezing and pump wavelength of 1550 nm and 775 nm [2].

The prototype of a high bandwidth squeezed light source at the telecom wavelength of 1550 nm was experimentally realized with a non-classical noise suppression of 0.3 dB and a bandwidth of more than 2 GHz [3].

A specially designed monolithic squeezing resonator experimentally demonstrated the feasibility of a high squeezing strength (3 dB) in addition to a bandwidth of more than 1.2 GHz [4].

 

 

 

GHzSqz_MeasurementPreliminary results show a non-classical noise suppression of more than 5 dB by using a custom made homodyne detector with a quantum efficiency of 99%.

 

 

 

 

This work is part of the EU project Q-Essence.

 

 

 

Contact: Stefan Ast

 

[1] Ast et al., Opt. Lett. 36, 3467 (2011)

[2] Steinlechner et al., Sensors 13, 565-573, (2013)

[3] Ast et al., Opt. Lett. 37, 2367 (2012)

[4] Ast et al., Opt. Exp. 21, 13572 (2012)

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