NuCrypt - CPDS-2000 - Correlated Photon Detection System

CPDS-2000 (1.25 GHz)

The correlated photon detection system (CDPS) consists of multiple fiber coupled 1.25 GHz gated single-photon detectors (SPDs) sensitive to telecom wavelengths followed by electronic processing. The system is ideal for measuring entangled light as it compiles statistics including singles counts and correlations between the various detectors and it can store raw data from the detectors for off-line processing. The SPD signals can be delayed before correlation to account for different fiber lengths between the detectors. Four digital output signals can be programmed to indicate a particular detection event, such as a correlation between any combination of detectors (Boolean function) thereby allowing interfacing to external equipment and enabling feed-forward conditional measurements. Product is also available in 50 MHz - CPDS-1000.

Basic Features

Count detection events on up to four detectors at 1.25 GHz gate rates
Count correlated detection events with programmable delays
Four programmable outputs that are Boolean functions (AND, OR, XOR, NOT) of the detector outputs (1.25 GHz update); e.g. the raw detector binary output on the individual detectors or an indication of any particular correlation being detected.
Large 8 Gb memory for storing raw data (storage can be synchronized to a trigger)
Generate N-bin histograms for optical pulses arriving at rate of (1.25/N) GHz
Optional DWDM optical link connects two CPDS-2000's; correlations between two spatially separated sites can be collected

Product Specifications

Attribute	Value	Units	Comments
Number of Detectors	1 - 4		-x suffix on model number where x {1,2,3,4}
Detector sensitivity range	1200-1600	nm
Photon Detection Efficiency	15	%	at 4x10^-5 dark count rate, 1550 nm
After-Pulse Probability	5	%	10 ns after detection event with a 1x10^-3 photon arrival rate
Dark-Count Probability	4x10^-5		Per gate at 15% efficiency
Noise equivalent power (NEP)	0.2 (3)	fW/√Hz	Achievable NEP for 1.25 GHz short pulses (CW light)
Gate Temporal-Location Resolution	< 1	ps	Control gate location
Detection Temporal Window	150	ps
Input Clock	1	V	Per detector
Correlation Delay	0-2¹⁹	clock cycles	Delay of detector clocks used to match long (to 100 km) external fiber delays
Clock Rate	1.25	GHz	Standard; inquire about other rates
Form Factor			3U 19" rack mountable box; 19x5 1/4 x 24 inches
Data storage memory	8	Gbit	Aggregate memory for all detectors; actual number of storable bits depends on the detection rate: for a 10^-4 singles count rate the compression factor is 500:1 which leads to 4 Terabits of storable raw data
Masking length	0,4,7,15,23,31,47,55,63	Gates	Number of gates after a detection event ignored by the processor to mitigate after-pulsing

Typical Applications

Measure entangled light distributed over different fiber lengths
High precision LIDAR ranging
Quantum key distribution (QKD)
General low-photon light detection

Product Photo & Diagram