  Random numbers are widely used for information security, cryptography,
stochastic modeling, and quantum simulations. Key technical challenges for
physical random number generation are speed and scalability. We demonstrate a
method for ultrafast generation of hundreds of random bit streams in parallel
with a single laser diode. Spatio-temporal interference of many lasing modes in
a specially designed cavity is introduced as a scheme for greatly accelerated
random bit generation. Spontaneous emission, caused by quantum fluctuations,
produces stochastic noise that makes the bit streams unpredictable. We achieve
a total bit rate of 250 terabits per second with off-line post-processing,
which is more than two orders of magnitude higher than the current
post-processing record. Our approach is robust, compact, and energy efficient
with potential applications in secure communication and high-performance
computation.
