Random numbers which are unpredictable and definitely unknown by anyone before they are generated are now used in a large number of real-world applications ranging from authentication, gaming, many online activities to simulations and optimizations. The development of a trusted randomness source is thus a necessity. In this work we present a simple design of a certifiable quantum random number generation and its. In particular we show how real-time low-latency randomness can be generated from measurements on time-bin photonic states every 0.12s. We generate a block of 2^13 random bits certifiable against the most powerful quantum adversary with its error bounded by 2^-64. Further our device is suitable for continuous operation giving it a potential application as a quantum randomness beacon.
We introduce our recent photonic quantum information processing experiments using the high-speed electro-optic modulator (EOM) based on a lithium niobate waveguides. First, we demonstrated the frequency shifter for single photons by using an optical single sideband (OSSB) modulator, which is based on the nested configuration of four phase modulators (PMs). By properly setting the RF modulation signal and the bias voltage to each PM, we can suppress unwanted sidebands to realize a frequency shifter that can tune the frequency of single photons with accuracy of an RF synthesizer. Using the OSSB modulator, we eliminated the frequency distinguishability between two single photons whose frequencies were different by 25 GHz, and as a result observed a Hong-Ou- Mandel interference with a visibility exceeding 90%. We also proposed and demonstrated a two-qubit controlled logic gate for time-bin qubits using a two-input, two-output optical switch. The switch enables us to individually perform different functions for two temporal bases as a time-dependent beam splitter, so that we can realize controlled-phase (C-Phase) gate for a time-bin qubit. We showed that the states of two separable single photons were entangled as a result of the C-Phase gate operation. We performed the quantum state tomography to obtain density matrices of the output states from the C-Phase gate for some specific input states, and confirmed that the averaged state fidelity to the pure states was 85%. These results indicate that the EOMs will be a useful tool for realizing advanced photonic quantum communication systems.
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