No abstract

The fluctuating intensity of a chaotic semiconductor laser is used for generating random sequences at rates up to 12.5 Gbits/s. The conversion of the fluctuating intensity to a random bit sequence can be implemented in either software or hardware and the overall rate of generation is much faster than any previously reported random number generator based on a physical mechanism. The generator's simplicity, robustness, and insensitivity to control parameters should enable its application to tasks of secure communication and calculation procedures requiring ultrahigh-speed generation of random bit sequences.

An all-electronic physical random number generator at rates up to 80  Gbit/s is presented, based on weakly coupled GaAs/Ga0.55Al0.45As superlattices operated at room temperature. It is based on large-amplitude, chaotic current oscillations characterized by a bandwidth of several hundred MHz and do not require external feedback or conversion to an electronic signal prior to digitization. The method is robust and insensitive to external perturbations and its fully electronic implementation suggests scalability and minimal postprocessing in comparison to existing optical implementations.

Zero-lag synchronization (ZLS) between chaotic units, which do not have self-feedback or a relay unit connecting them, is experimentally demonstrated for two mutually coupled chaotic semiconductor lasers. The mechanism is based on two mutual coupling delay times with certain allowed integer ratios, whereas for a single mutual delay time ZLS cannot be achieved. This mechanism is also found numerically for mutually coupled chaotic maps where its stability is analyzed using the Schur-Cohn theorem for the roots of polynomials. The symmetry of the polynomials allows only specific integer ratios for ZLS. In addition, we present a general argument for ZLS when several mutual coupling delay times are present.

This Letter was published online on 19 March 2010 with an incorrect caption to Fig. 4. Figure 4's caption should read as ''(Color online) 10 ns recording of the time dependent intensity of two semiconductor lasers (thin blue and thick red).To demonstrate the slow decorrelation of the intensities with increasing time we show in panel (a) (dashed line) the intensity of the laser after a delay of 4 1 . Corresponding correlation values can be seen in Fig. 3.''