True random number generators are in high demand for secure cryptographic algorithms. Unlike algorithmically generated pseudo-random numbers, they are unclonable and non-deterministic. In this paper, we extract the white noise from stochastic Brownian Markov trajectories and use it to generate random numbers that qualify NIST standard tests of randomness. We trap colloidal particles in water using optical tweezers and record its confined Brownian motion in real-time. Next, in a two-step process, we use the initial section of incoming data to train and calibrate our iterative algorithm on the trap stiffness and viscosity of the solution based on the autocorrelation and power spectrum properties of the noise; then, we extract random arrays from the next section of the data. Interestingly, we get the best random number sequence for the best calibration. We test the random number sequence, which we have obtained, using standard randomness tests and observing the randomness to improve with increasing sampling frequencies.1 In the next steps, we extend this method to a wider class of processes, such as an optically trapped particle modulated by a square pulse or an external colored noise generated by an Ornstein Uhlenbeck process – we estimate the timescale of both the modulation and viscous effect using our algorithm.
We provide a multiple-sinusoid modulated optical tweezers based method to perform microrheology of a sample over a large frequency band in a one shot. So we feed the trapped particle with a square wave and a superposition of multiple-sinusoid of specific frequency and amplitude to achieve our purpose towards active microrheology. To maintain the SNR upto a certain level for the entire frequency range we increase the amplitude at high frequency in our setup. We measure the parameters of the complex fluid by extracting the phase responses at each frequency of the particle with a high SNR value compared to passive microrheology. We perform this method for a various concentrations of polyacrylamide-water solution and obtain a good agreement of the fluid parameters with the theoretical values.
Surface effects are crucial in several mesoscopic phenomena, especially those concerning biological entities. Here we determine the effects of Van der Waals forces at relatively long range ( 80 nm) by optically trapping a probe particle close to a large silica particle and modulating the spatial position of the probe employing oscillating optical tweezers. This method has greater signal-to-noise in the experimentally measured probe-response as compare to that obtained from measurements of Brownian fluctuations. We quantify the H-value experimentally by analyzing the amplitude response of a single trapped particle in comparison to numerically expected results by employing chi-square fitting, and obtain good agreement with the known H-value for the system.
Conference Committee Involvement (3)
Contemporary Trends in Optics 2019 (CoOpt-2019)
20 May 2019 |
Contemporary Trends in Optics 2017 (CoOpt-2017)
18 December 2017 |
Space Astronomy and Telescope Making Workshop
24 March 2017 |
Course Instructor
NON-SPIE: Quantifying the binding kinetics of peripheral membrane proteins
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