An add-on implementation of frequency compensation for qcrypto.
Requirements:
- Python 3.8 and above, running in Linux
gcc
(if runningfreqcd
, preferably in PATH for auto-compilation)
# Remote installation
pip3 install git+https://github.com/s-fifteen-instruments/fpfind.git
# Local installation
git clone https://github.com/s-fifteen-instruments/fpfind.git
cd fpfind && pip3 install .
Binaries and scripts will be exposed to the path; commonly used scripts are listed below.
fpfind -t {TIMESTAMPS1} -T {TIMESTAMPS2}
freqcd -X -udF fpipe -f 568 < {TIMESTAMPS}
[costream -V5 ... |] freqservo -V5 -udF fpipe -f 568
parse_timestamps -A1 -X -p {TIMESTAMPS}
Quantum key distribution requires some form of clock synchronization to retain high signal-noise ratio when pairing photon detection/generation events. This is usually achieved by having a stable clock (e.g. Rb clock, GPS receiver) or a separate clock transfer channel.
Timing correlated photons used in the QKD itself can also be used as a resource for clock synchronization, by identifying and tracking the timing delay
This library implements the frequency compensation modules supplementing the core qcrypto QKD software stack, and a reference usage can be found in QKDServer.
Components for frequency compensation (implemented in this library) are highlighted in yellow below.
In particular:
freqcd.c
performs frequency correctionfpfind.py
replacespfind.c
for initial frequency estimationfreqservo.py
performs frequency drift estimation
- The FFT buffer size is limited to 2**31 bins due to the implicit casting to
int32
performed internally bynp.bincount
on older versions ofnumpy
. This corresponds to a buffer order value upper bounded toq = 31
forfpfind
. To bypass this limitation, supply an alternative implementation fornp.bincount
.
Certain issues may appear when attempting an install on RaspbianOS:
- Importing
numpy
yields the error message statinglibopenblas.so
could not be found (this is the underlying linear algebra library for Numpy); installing thelibopenblas-dev
library fixes this, e.g.apt install libopenblas-dev
Version tags (as of v2) follow semantic versioning, with a build string indicating the date of release in "YYMMDD" format, e.g. v2.0.0+2410224. This allows clear indication to the user whether the local version is severely outdated, while maintaining the clarity of semantic versioning. Versioning is performed by:
- Modifying the version field in
pyproject.toml
, with no "v" - Adding a basic git tag associated with the commit, with "v" prepended
Commit messages to roughly follow Angular commit message guidelines (which aligns with the Conventional Commits specification). The type should be one of the following: feat, fix, perf, refactor, style, test, docs. If a scope is provided, it should be one of:
- fpplot
- freqcd
- freqservo
- parser (for both timestamp and epoch)
Commit messages can be automatically checked using pre-commit
, after installing:
pre-commit install --hook-type commit-msg