| name | meaning | type | used by |
|---|
| /dev/xdma0_user | FPGA registers for control and monitoring | memory map; addresse with respect to bytes, values 4bytes=32bit | hw_alice.py / hw_bob.py, hws.py gc |
| /dev/xdma0_c2h_0 | global counter (qubit identifier) and click result of detected qubit | FPGA to OS fifo 128bit/word | gc |
| /dev/xdma0_h2c_0 | global counter of detected qubit | OS to FPGA fifo 128bit/word | gc |
| /dev/xdma0_h2c_1 | RNG values | OS to FPGA fifo 128bit/word | |
| /dev/xdma0_c2h_2 | TDC timestamps, global counter, click result for calibration | FPGA to OS fifo 128bit/word | hws.py, hw_bob.py |
| /dev/xdma0_c2h_3 | angles (rng values of detected qubits) | FPGA to OS fifo 128bit/word | node, qber |
| ~/qline/hw-control/startstop.s | start and stop the raw key generation | unix stream; each byte a command | node, qber |
| ~/qline/hw-control/result.f | measurement result (on Bob only) | unix fifo; each byte a result | node, `qber |
The dataflow when you run qber
| name | meaning |
|---|
hw_alice.py; hw_bob.py | manually change hardware settings individually on Alice and Bob (see help message of the sript) |
hws.py | hardware init procedures controlled by Alice |
gc | background process to send gc from Bob to Alice and start/stop raw key generation; gc_client is waiting for start/stop from another program |
qber | calculate qber (for calibration only) |
node | send start/stop to gc_client; process raw key to final key (qber estimation, error correction, privacy amplification) |
kms | key management service; takes key from node |
| name | meaning | edited by |
|---|
| ~/hw_control/config/defaults.txt | initial hardware parameters | Admin |
| ~/hw_control/config/tmp.txt | running hardware parameters | hw_bob.py / hw_alice.py, hws.py, |
| ~/config/ | high level configuration for all programs | Admin (through gen_config) |
Meaning of paramters in config/defaults.txt and config/tmp.txt:
| name | value | meaning | only on |
|---|
| angleX | [-1,1] | the four angle values to be applied onto the phase modulator | |
| am_mode | off | amplitude modulator is not sending pulses | Alice |
| single | single pulse every two repetitions (at 40MHz) | Alice |
| double | double pulse every repetition (qubits at 80 MHz) | Alice |
| single64 | single pulse every 64 repetitions | Alice |
| am_shift | [0,640) | fine shift the amplitude modulator in units of 1/10 qubit distance | Alice |
| pm_mode | off | 0 angle everywhere | |
| seq64 | 64 periodic sequence of alternating, linearly increasing angle values | |
| fake_rng | periodic, predefined rng sequence | |
| true_rng | true rng | |
| pm_shift | [0,640) | Same as am. In case of pm_mode == *_rng the value is taken mudulo 10 | |
| fiber_delay_mod | [0,32) | delay angles before postprocessing in units of double repetition rate modulo 32 | |
| fiber_delay | [0,..] | same but full range | |
| insert_zeros | {on,off} | insert zeros every 16 repetitions | |
| zero_pos | [0,16) | at this position | |
| feedback | {on,off} | compensate interferometer drift based on click result at the zeros position | Bob |
| am_bias | [-10,10] | bias in volt for background suppression | Alice |
| vca | [0,5] | bias in volt for attenuation to single photon level | Alice |
| qdisatnce | [-1,1] | fine tune the distance of the double pulse around 5ns | Alice |
| SPD_mode | {gated, free} | gated or continuous mode | Bob |
| SPD_deadtime | [8,100] | deadtime in microseconds | Bob |
| SPD_eff | {20,30} | detection efficiency | Bob |
| gate_delay | [0,12000] | delay TTL gate pulse to SPD in ps | Bob |
| gate_delayX | [0,404) | internal values for gate_delay | Bob |
| t0 | [0,100] | detection time offset in units of 20ps (to fine align the gates) | Bob |
| polX | [0,5] | voltage to the 4 axis polarization controller | Bob |