Dear Editor,

please find enclosed a manuscript describing a quantum random number generator
that is based on homodyne detection, which features a very efficient method
for cleaning up the raw entropy contained in the physical measurement process,
and which is based on so-called linear feedback shift registers. This allows
our device to provide a rate of random bits to be extracted from a physical
measurement, where the source of randomness is the quantum fluctuations of the
electromagnetic field in a vacuum state - a source of randomness that is hard
to influence from outside.

The implementation we report on is between an experimental physics paper, and
a mathematical algorithm that is particularly lean on resources, and thus
allows us to generate clean random numbers at a very high rate. In the
manuscript at hand, we were limited by the ability to read in the random
numbers after the processing to remove bias etc into a host, and observed
480Mbit/sec according to the USB2.0 specification. The scheme easily scales up
to higher rates for methods that are able to consume random numbers at an
appropriate rate.

Quantum random number generators have been around for a while, in various
implementations. Similarly, the specific method to use the physical detection
of the vacuum fluctuation of the electromagnetic field has been implemented
before. What is new in our scheme is that we combine this with an extremely
resource-efficient randomness  extractor. This randomness extractor may be
also interesting for other physical random number generators, and therefore
may be appealing to a wider community that those who are concerned with a
quantum physical process to generate physical randomness.

We hope that Physical Review Applied is an appropriate platform for this work,
as it clearly has left the realm of quantum physics only, but showcases the
use of a physical process to efficiently provide random numbers, which should
be of reasonably widespread interest in a time where trustable encryption
becomes more and more important.

With Best Regards on behalf of all authors,

Christian Kurtsiefer