Entanglement Source

EPR-XX-YY Series User’s Guide

Key element to practical quantum networking and quantum sensing

Entangled photon sources are critical to the applications in quantum computing, provably quantum secure cryptography, and quantum-enhanced metrology. QCI’s general purpose entangled photon source allows users to access the entangled photons for their specific application. QCI’s entanglement source utilizes a fiber coupled periodically poled lithium niobate via spontaneous parametric down-conversion (SPDC) to produce broadband entangled photons to the entire telecom C-band. QCI’s fiber coupled source is highly customizable, robust, compact, and for both academic, R&D, and industrial applications. The schematic graph of our entangled photon module is shown below:


Figure (a) illustrates the schematic of the SPDC process, a phenomenon in quantum optics wherein a single photon, known as the 'pump photon,' of higher energy, converts into a pair of photons: a signal photon and an idler photon. This conversion process obeys the conservation of energy and momentum. Figure (b) shows the conceptual diagram of entanglement photon pairs (each pair connect using red dashed line) via SPDC processes. From the incident pump light in the visible band (775.1 nm), photon pairs are simultaneously produced under the quasi-phase matching condition, in which signals and idlers are generated in the entire telecom C-band region. The relation between the pump, idler-signal frequency under quasi-phase matching condition is

Screenshot 2024-02-28 at 10.23.57 AM

Telecom band photon pairs generator Support high dimensional encoding Plug and play system


  1. Quantum Key Distribution

  2. Quantum Authentication

  3. Quantum Metrology

  4. Quantum Networking

  5. Time Synchronization System

  6. Fundamental Physics Studies


QCI’s entangled photon source uses spontaneous parametric down-conversion (SPDC) in a quasi-phase-matched lithium niobate waveguide to create a pair of energy-time entangled photons at Telecom wavelength. It covers the entire telecom C-band Dense Wavelength Division Multiplexing (DWDM) ITU Grid thus compatible with existing fiber-optic communication infrastructure. With an integrated 775 nm pump laser, this fiber-coupled integrated sources produce >60 mega photon pairs per second.. Our entangled photon source can achieve zero-time delay second-order correlation function [g(2) (τ = 0)] value of <0.1 thus producing high-brightness heralded single-photon source ideal for quantum optics applications. The QCI’s integrated solution will offer the generation of (customizable) transform-limited single photons over broadband of telecom wavelengths, essential for quantum networks applications in quantum computing, provably secure cryptography, and quantum-enhanced metrology.

Our rackmountable entangled photon source demonstrates remarkable stability, maintaining stability over 12 hours, enduring prolonged periods of reliable entanglement. Our source’s brightness enables its operation in photon starved environments, making it resilient for both fiber and free space transmission across extensive distances. Utilizing either their polarization or time-frequency entanglement, the photon pairs form our source can be used for a myriad of applications.


Generation rate (pairs/power/sec)

5 million pairs/1uW/sec

Coincidence-to-accidental count (CAR)


Wavelength ranges

1534.3 nm ~ 1566.4 nm

Operating Temperature

15 C to 55 C

Laser source

775 nm


1. Laser power vs intrinsic count rate (16 pairs)


The above figure shows the pump laser power vs the idler intrinsic counts rate, in which the conts rate is integrated among all 16 entanglement pairs.

2. Counts rate (one idler) stability over time with the pump power at 12 uW.

figure 3

3. CAR stability over time (1 pair)

figure 4

EPR-XX-YY Series Product Family


XX IT: integrated module ST: standalone module

YY No number for standalone Number of channels, from 2 to 48


Hardware startup

Both input and output of the module are panda polarization maintaining cable (FC/APC). Carefully clean FC/APC connector (noting whether the cable is SM or PM) before connect to the FC bulkhead connector of the entanglement module. Please also note that the input power entering the module should not exceed --dBm( - - mW).

Software startup

User control: Adjust center wavelength of pump photon (tunable laser) -> TEC automatic control -> optimize waveguide phase matching


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