In a nutshell, the Photonic Instrument employs one of these IP cameras:-

inside a windowless integrating sphere, dimly lit with a white LED arranged like this behind the camera:-

to produce noisy images that look like this:-

And each image’s JPEG file is the entropy. It’s an extremely correlated bit fixing source, averaging ~21.4kB in size. Such a file’s entropy is conservatively assessed for cryptographic purposes at 21kb, and the instrument can produce 10 frames per second. If you exclude the overhead for entropy extraction, the Photonic Instrument creates about 210kb of entropy per second.

Following entropy extraction to generate a 500kB file of independent and identically distributed random bytes, the rudimentary ent program gives the following encouraging verdict:-

$python3 ./trng.py 500000 | ent
Entropy = 7.999640 bits per byte.
Optimum compression would reduce the size
of this 500000 byte file by 0 percent.
Chi square distribution for 500000 samples is 250.16, and randomly
would exceed this value 57.39 percent of the times.
Arithmetic mean value of data bytes is 127.3968 (127.5 = random).
Monte Carlo value for Pi is 3.144924580 (error 0.11 percent).
Serial correlation coefficient is 0.000307 (totally uncorrelated = 0.0).

The output also passes diehard but that doesn’t easily fit on this summary page ❗️