Random number generation is necessary for data security, for encryption keys and passwords, and computer simulations of complex systems such as the weather and financial markets. As such, there is a strong demand for random number generators that are small enough for chip-scale integration while also offering a fast generation rate.
Researchers from King Abdullah University of Science and Technology (KAUST), King Abdulaziz City for Science and Technology, and the University of California at Santa Barbara demonstrated micro-LEDs can generate random numbers at gigabit-per-second (Gbps) speeds.
Micro-LEDs developed by KAUST researchers can serve as quantum random number generators, achieving an ultra-high generation rate of 9.375 Gbps. Courtesy of KAUST.
The most robust and reliable way to generate true random numbers is to sample and digitize a physical process underpinned by the randomness of quantum mechanics. Thermal noise, chaos, and jitter from electronic and optoelectronic devices have all been investigated in the past. Micro-LEDs consume less power and require simpler electronic and photonic system architectures than other competing technologies.
The researchers reported that intensity fluctuations in the spontaneous emission from blue gallium nitride (GaN) micro-LEDs, ranging in size from 5 to 100 μm, can serve as a quantum random number generator with an ultra-high generation rate of 9.375 Gbps.
The idea of using LEDs to generate numbers isn't new. Over the past decade, researchers have explored measuring photon number and arrival time. However, these past trials provided much slower generation rates, typically on the scale of no more than a few hundred megabits per second.
“Systems relying on single-photon detection typically extract only two bits per sampling cycle, whereas our system achieves six bits by leveraging intensity fluctuations,” said researchers Heming Lin and Boon Ooi.
Importantly, for any quantum random number generator to be trusted, its output must be stringently tested to ensure that it is sufficiently random. According to the researchers, the tests developed by the U.S. National Institute of Standards and Technology (NIST) are considered the gold standard. The KAUST team tested a variety of micro-LEDs with different sizes — ranging from 5 × 5 μm² to 100 × 100 μm² — and drive currents ranging from 0.5 to 100 mA, which all passed the NIST tests.
In the future, researchers will focus on boosting generation rates by creating 2D arrays of micro-LEDs that enable parallel random number generation. They are also planning to create a fully integrated system, rather than using discrete components.
The current KAUST system comprises a GaN micro-LED, which is temperature stabilized using a thermoelectric cooler and has its light emission fed to an avalanche photodetector. This is connected to a sampling oscilloscope via an electronic amplifier.
The next step is to integrate an on-chip photodetector with the micro-LED and subsequently incorporate all the required electronic components to realize a fully integrated quantum random number generator chip.
The research was published Optics Express (www.doi.org/10.1364/OE.559375).