A tunable tunnel diode based digitized noise source includes a digitized noise source for producing a sequence of random digital signals. The digitized noise source includes a tunnel diode for providing a current signal that includes quantum shot noise. The digitized noise source can also include a current-to-voltage converter coupled to the tunnel diode for converting the current signal to a voltage signal, a filtering and amplification circuit coupled to the current-to-voltage converter for producing an amplified voltage signal, and a digitization circuit for converting the amplified voltage signal into the sequence of digital signals that represents random bits. The tunable tunnel diode based digitized noise source further includes an entropy estimator coupled to the output of the digitization circuit for estimating an entropy of the sequence of digital signals and for providing a feedback bias voltage to the tunnel diode.