DOI: 10.5281/zenodo.13753477
title: Cryogenic feed-forward of a Photonic Quantum State

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Supplemental material for 'Cryogenic feed-forward of a Photonic Quantum State'
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Simulation:
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simulation.py
	- simulation script used to calculate expected g(2)(0) values for various experimental settings
	- uncomment the the parts of the setting you want to plot
	- the POVM matrix of the 4 pixel SNSPD calculated by Timon Schapeler
	- used to calculate the response of the 4 pixel detector to a given photon number


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G2 Measurements:
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Coincidences_xxx.csv
	bidirectional coincidence Histogramms of various events (see below) at an idler mean photon number
	The collums indicate the number of counts in a given timebin
	timebins are indicative of the relative time difference between two events
	binsize: 250ps
	
	Row contents are:
		no photon number resolution
		0: coincidence HBT detector 1 and modulator trigger
		1: coincidence HBT detector 2 and modulator trigger
		2: coincidence HBT detector 2 and virtual channel of detector 1 heralded with the modulator trigger
		3: coincidence HBT detector 1 and virtual channel of detector 2 heralded with the modulator trigger
		4: coincidence HBT detector 1 and detector 2
		selecting single photons
		5: coincidence HBT detector 1 and modulator trigger
		6: coincidence HBT detector 2 and modulator trigger
		7: coincidence HBT detector 2 and virtual channel of detector 1 heralded with the modulator trigger
		8: coincidence HBT detector 1 and virtual channel of detector 2 heralded with the modulator trigger
		9: coincidence HBT detector 1 and detector 2
		selecting two photons
		10: coincidence HBT detector 1 and modulator trigger
		11: coincidence HBT detector 2 and modulator trigger
		12: coincidence HBT detector 2 and virtual channel of detector 1 heralded with the modulator trigger
		13: coincidence HBT detector 1 and virtual channel of detector 2 heralded with the modulator trigger
		14: coincidence HBT detector 1 and detector 2

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Cryogenic Electronics
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Threshold Sweep Map.csv
	observed countrate under pulsed coherent state input. The repetition rate 600kHz for the pulsed 1550nm laser.
	axis: Threshold settings ranging from 30mV to 150mV in 2mV steps
	The columns correspond to a sweep of the high level threshold.
	The rows correspond to a sweep of the low level threshold.

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Source:
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SHG_Spectrum.csv
	The resulting spectrum of the SHG conversion with the periodically poled LiNbO3 crystal. The intensity is normalized to the maximum amplitude.

JointSpectrum_Wavelength.csv
JointSpectrum_Countrate.csv
	Dataset of the joint spectral intensity in counts/s. The used incremental wavelength steps are given in the file. 
	The presented joint spectrum is acquired after the PDC-process.

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Modulator:
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ModulatorSweep_Output.csv
ModulatorSweep_Voltage.csv
ModulatorSweep_Wavelength.csv
	Characterisation scan of the cryogneic electro-optic modulator. The wavelength and voltage of modualtor is swept while the throughput power is acquired.
	The dataset is acquired with a narrow band laser with a FWHM of 1pm. The dataset is plotted in the supplementary material.

Time_ModulationTrace.csv
DrivingSignal_ModulationTrace.csv
ResponsSignal_ModulationTrace.csv
	Optical response of the croygenic photonic circuit when light is detected in the idler arm. The driving signal is generated by the SNSPD, amplifier, discriminator and modulator driver.
	The driving signal is acquired from the cryogneic circuit into a room temperature 50Ohm load. 
	The response signal of is acquired by sending constant power through the electro-optic modulator at 1550nm.
	The driving signal is generated by the complete cryogenic SNSPD, amplifier, discriminator and modulator driving connected to the modulator.
	The signal is acquired with a room temperature photodiode. 
	The time steps are given in the file.

modulator_S_parameters.csv
	The measured S parameters of the modulator measured with CW light and a photodiode
	Collums are: frequency [MHz] : S11 amplitude [dB] : S11 Phase [Degrees] : S21 amplitude [dB] : S21 Phase [Degrees]

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4-pixel SNSPD:
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Traces_SNSPDTraces.csv
Time_SNSPDTraces.csv
	1000 signal traces at the output of the SNSPD. These presented traces are acquired after the cryogenic amplifier with a room temperature oscilloscope with a 50Ohm load.
	The signals time steps are given in the second file. The dataset is displayed in figure 2b) of the main manuscript. 

Detector_bias_countrate.csv
	countrate observed after the triggering electronics when scanning the SNSPD bias current. SNSPD illuminated with pulsed 600kHz repetition rate attenuated coherent state.
	Collums are: Voltage over 110 k ohm biassing resistor [mV] : countrate when illuminated : countrate when input blocked



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Amplifiers:
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first_amp_high_power_S_parameters.csv
	S-parameters for the first amplifier stage operated at ∼50 μA Base current and 0.6 V at the collector
first_amp_low_power_S_parameters.csv
	S-parameters for the first amplifier stage operated at ∼17 μA Base current and 0.4 V at the collector
second_amp_S_parameters.csv
	S-parameters for the second amplifier stage

all files:
	Collums are: frequency [MHz] : S11 amplitude [dB] : S11 Phase [Degrees] : S21 amplitude [dB] : S21 Phase [Degrees] : S12 amplitude [dB] : S12 Phase [Degrees] : S22 amplitude [dB] : S22 Phase [Degrees]